Re: [fpc-devel] Fwd: While - Otherwise Statement

[Martin Schreiber]

On Tuesday 13 October 2015 23:25:03 Michael Van Canneyt wrote:

> > But the existence of such a continue block shows the fundamental issue on
> > which a decision is needed. should (if a volunteer for a patch exists)
> > every little "save one statement in your code helper" be added? Because
> > there are thousands of them, and if you add them all the readability of
> > code will go down, because you need to first learn them all.
>
> I think the answer to your question is a clear and loud "NO".
>
> The argument that we can refrain from using these new features does not
> hold, because other people will be using it, and we will have to know all
> of it to be able to understand their code.
> None of these features will automagically make Object Pascal a popular
> language.

>
> However, I seem to be one of the very few thinking this given the
> enthousiasm with which people are discussing this.
>

We are at least two people. :-)

> Soon I will be forced to emigrate to Javascript country.

Or to MSElang? ;-)

Martin
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Mark Morgan Lloyd]

Michael Van Canneyt wrote:

But the existence of such a continue block shows the fundamental issue 
on which a decision is needed. should (if a volunteer for a patch 
exists) every little "save one statement in your code helper" be 
added? Because there are thousands of them, and if you add them all 
the readability of code will go down, because you need to first learn 
them all.


I think the answer to your question is a clear and loud "NO".

The argument that we can refrain from using these new features does not 
hold,
because other people will be using it, and we will have to know all of 
it to be able to understand their code.
None of these features will automagically make Object Pascal a popular 
language.


However, I seem to be one of the very few thinking this given the 
enthousiasm with which people are discussing this.


For what it's worth, I agree with you. It's one thing restoring 
something like the "inline if" (or a functional equivalent) which was in 
ALGOL and is regularly used in most current languages, but doing 
something like adding a completely new flow control construct which has 
no significant precedent in other languages is much more difficult to 
defend.


Soon I will be forced to emigrate to Javascript country. Despite all its 
drawbacks, it remains at least a simple language. a dozen keywords and 
you're done. No wonder Node.js is so popular.

Compare that with the jungle we're making of it... :(


At the same time, I think it's worth distinguishing three distinct cases 
that contribute to syntax complexity.


The first is the case that you had in early ALGOL implementations, where 
there was limited support for external libraries and where every detail 
of control of- for example- file open mode had to be expressed as part 
of the language syntax.


The second is the case where a language has a fairly verbose syntax, but 
where this is used to define a rich set of general-purpose flow-control 
and data-definition constructs. This is where Pascal is at.


The third case is modern C++, Javascript and so on which grossly 
overload the limited ASCII character set and where abusing even the 
lowly parenthesis can have non-obvious effects. Then there's the issues 
they have with things like "static", and their use of "std::something" 
as quasi-directives.


I'm still struggling with a mainframe emulator, originally written in 
Javascript, where around half of the complexity was due to the lack of 
any support for multithreading. I also think that the recent forking of 
the Scratch graphical language, where a significant proportion of the 
community has rejected MIT's attempts to reimplement it in Javascript, 
indicates that there's an increasing awareness that both the language 
and its typical implementations- i.e. embedded in a browser or as 
ActionScript in Flash- leave much to be desired.


And Node.js is lipstick on a pig.

--
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markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Walter Prins]

On 14 October 2015 at 07:28, Martin Schreiber  wrote:

> On Tuesday 13 October 2015 23:25:03 Michael Van Canneyt wrote:
> > However, I seem to be one of the very few thinking this given the
> > enthousiasm with which people are discussing this.
> >
>
> We are at least two people. :-)
>

For what it's worth, with me that's at least 3.


> > Soon I will be forced to emigrate to Javascript country.
>
> Or to MSElang? ;-)
>

Or Scala?  :-P  (Digressing a bit more in this vein, I've been feeling the
pull of more functional languages lately, in particular Scala, which if you
don't know is a functional OO hybrid language that targets the JVM.  I
actually wish something similar happened in the Object Pascal space.  C#
inspired F#.   Java inspired Scala.  Delphi/FPC inspired/inspires ...?
Further aside, for those interested in more functional programming and
Scala, watch this video: https://goo.gl/chdMlv   In a different vein,
there's also the Rust language which is another language seems well worth
learning and brings new ideas to the table well above and beyond syntactic
sugar But enough of that, hope that's not been too off topic!)

Walter
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Nikolai Zhubr]

Hi all,
14.10.2015 23:44, Walter Prins:



On 14 October 2015 at 07:28, Martin Schreiber > wrote:

On Tuesday 13 October 2015 23:25:03 Michael Van Canneyt wrote:
>  However, I seem to be one of the very few thinking this given the
>  enthousiasm with which people are discussing this.
>

We are at least two people. :-)

For what it's worth, with me that's at least 3.


Me too! Me too!
That's 4 already :-)


Thank you,
Nikolai






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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Jonas Maebe]

Sven Barth wrote:

The intrafunctional gotos not really. But the interfunctional ones
(modeswitch nonlocalgoto in 2.7.1+) might mess with managed types ;)


The compiler should give an error if you try to "goto" out of or into a 
frame than needs initialisation/finalisation.



Jonas
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Michael Van Canneyt]

On Mon, 12 Oct 2015, wkitt...@windstream.net wrote:


On 10/12/2015 03:43 PM, Martin Frb wrote:
Actually the above does not represent what the actual feature request is 
about


The "else" is to be executed, after the while (even if the while looped 
ZERO

times).
But it is to be skipped if the while exited via break (and only then).

For that reason "else" or "otherwise" are badly chosen keywords. Because 
they

imply a different function.


exactly my and others' points... "and" would be better but then one might 
just as easily use a goto to jump around that part if break was used to get 
out of the loop...


anyway, it seems that no matter what the discussion, it won't make it into 
the compiler... that according to another post from a compiler dev ;)


Maybe my remark was not clear.

I'm not against this *functionality*.

I merely pointed out that *the syntax using 'else'* 
is not going to make it because it breaks backwards compatibility.


If another keyword is used: no problem.

I don't understand why anyone would want this marginal functionality and thus 
(again) needlessly complicates the language, but hey, it's a (mostly) free world


Alas, the monstrosity that Object Pascal syntax is becoming is less and less 
appealing by the day, it's simply frightening...


Michael.
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Sven Barth]

Am 13.10.2015 08:36 schrieb "Jonas Maebe" :
>
> Sven Barth wrote:
>>
>> The intrafunctional gotos not really. But the interfunctional ones
>> (modeswitch nonlocalgoto in 2.7.1+) might mess with managed types ;)
>
>
> The compiler should give an error if you try to "goto" out of or into a
frame than needs initialisation/finalisation.

Ah, ok, so we're already checking that. Good ^^
Then it's mostly the "bad karma" of goto I'd say ;)

Regards,
Sven
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Mark Morgan Lloyd]

wkitt...@windstream.net wrote:

On 10/13/2015 04:32 AM, Michael Van Canneyt wrote:



On Mon, 12 Oct 2015, wkitt...@windstream.net wrote:


On 10/12/2015 03:43 PM, Martin Frb wrote:
Actually the above does not represent what the actual feature 
request is about


The "else" is to be executed, after the while (even if the while 
looped ZERO

times).
But it is to be skipped if the while exited via break (and only then).

For that reason "else" or "otherwise" are badly chosen keywords. 
Because they

imply a different function.


exactly my and others' points... "and" would be better but then one 
might just
as easily use a goto to jump around that part if break was used to 
get out of

the loop...

anyway, it seems that no matter what the discussion, it won't make it 
into the

compiler... that according to another post from a compiler dev ;)


Maybe my remark was not clear.

I'm not against this *functionality*.

I merely pointed out that *the syntax using 'else'* is not going to 
make it

because it breaks backwards compatibility.


a... my bad... sorry 'bout that... i've been thinking about this, 
too... 'else' and 'otherwise' mean the same thing... what they seem to 
be looking for is 'aswell'...



foo := 0;
while foo < 100 do
  begin
inc(foo);
  end;
aswell
  begin
dec(foo);
  end;


either 'aswell' or 'aswellas'... while foo is less than 100 increment 
foo as well as decrement foo when it is no longer less than 100...


If somebody really has to do this wouldn't "also" be a better choice to 
avoid (getting close to overloading "as"? :-/


--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[wkitty42]

On 10/13/2015 04:32 AM, Michael Van Canneyt wrote:



On Mon, 12 Oct 2015, wkitt...@windstream.net wrote:


On 10/12/2015 03:43 PM, Martin Frb wrote:

Actually the above does not represent what the actual feature request is about

The "else" is to be executed, after the while (even if the while looped ZERO
times).
But it is to be skipped if the while exited via break (and only then).

For that reason "else" or "otherwise" are badly chosen keywords. Because they
imply a different function.


exactly my and others' points... "and" would be better but then one might just
as easily use a goto to jump around that part if break was used to get out of
the loop...

anyway, it seems that no matter what the discussion, it won't make it into the
compiler... that according to another post from a compiler dev ;)


Maybe my remark was not clear.

I'm not against this *functionality*.

I merely pointed out that *the syntax using 'else'* is not going to make it
because it breaks backwards compatibility.


a... my bad... sorry 'bout that... i've been thinking about this, too... 
'else' and 'otherwise' mean the same thing... what they seem to be looking for 
is 'aswell'...



foo := 0;
while foo < 100 do
  begin
inc(foo);
  end;
aswell
  begin
dec(foo);
  end;


either 'aswell' or 'aswellas'... while foo is less than 100 increment foo as 
well as decrement foo when it is no longer less than 100...


i don't see a need for it because in this case if one wants foo to only get to 
99, then they should use 99 as their count...



foo := 0;
while foo < 99 do
  begin
inc(foo);
  end;


at the end of the loop, foo will equal 99... but it is also a very simple 
example...



If another keyword is used: no problem.


ok...


I don't understand why anyone would want this marginal functionality and thus
(again) needlessly complicates the language, but hey, it's a (mostly) free
world

Alas, the monstrosity that Object Pascal syntax is becoming is less and less
appealing by the day, it's simply frightening...


it seems that way... but it doesn't mean that we have to use it... we can stay 
with the traditional ways and means within whatever it becomes as long as they 
don't change with these undesirable extensions...


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Re: [fpc-devel] Fwd: While - Otherwise Statement

[David W Noon]

-BEGIN PGP SIGNED MESSAGE-
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On Mon, 12 Oct 2015 22:34:03 -0300, Flávio Etrusco
(flavio.etru...@gmail.com) wrote about "Re: [fpc-devel] Fwd: While -
Otherwise Statement" (in

Re: [fpc-devel] Fwd: While - Otherwise Statement

[David W Noon]

-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1

On Mon, 12 Oct 2015 21:32:07 -0400, Wkitty42 (wkitt...@windstream.net)
wrote about "Re: [fpc-devel] Fwd: While - Otherwise Statement" (in
<561c5f17.4070...@windstream.net>):

[snip]
> that looks very much like what some would consider goto
> statements... does the leave return to the top of the previous loop
> or does it drop to the next statement in the previous loop?

It leaves the loop at the END statement that matches the DO statement
as labelled. So it goes to the next statement in the surrounding loop.

>> If the label is omitted then the immediately containing loop is
>> left.
> 
> "immediately containing loop" meaning loop_3 if we're in loop_3?

Correct. It's the same as break.

> yup! and i did catch the THEH->THEN oops... no problems there O:)

Ageing eyes, I'm afraid. When I remove my contact lenses at night I
have very distorted corneas (keratoconus) and cannot easily
distinguish an H from an N. ... :-(
- -- 
Regards,

Dave  [RLU #314465]
*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Ralf Quint]

On 10/13/2015 1:32 AM, Michael Van Canneyt wrote:



I don't understand why anyone would want this marginal functionality 
and thus (again) needlessly complicates the language, but hey, it's a 
(mostly) free world


Alas, the monstrosity that Object Pascal syntax is becoming is less 
and less appealing by the day, it's simply frightening...

+1

Ralf

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Re: [fpc-devel] Fwd: While - Otherwise Statement

[wkitty42]

On 10/13/2015 09:40 AM, Mark Morgan Lloyd wrote:

wkitt...@windstream.net wrote:

a... my bad... sorry 'bout that... i've been thinking about this, too...
'else' and 'otherwise' mean the same thing... what they seem to be looking for
is 'aswell'...


foo := 0;
while foo < 100 do
  begin
inc(foo);
  end;
aswell
  begin
dec(foo);
  end;


either 'aswell' or 'aswellas'... while foo is less than 100 increment foo as
well as decrement foo when it is no longer less than 100...


If somebody really has to do this wouldn't "also" be a better choice to avoid
(getting close to overloading "as"? :-/


it might... i don't know anything about "as" because i've never used it... what 
does it do?


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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Martin Frb]

wkitt...@windstream.net wrote:
a... my bad... sorry 'bout that... i've been thinking about this, 
too... 'else' and 'otherwise' mean the same thing... what they seem 
to be looking for is 'aswell'...



foo := 0;
while foo < 100 do
  begin
inc(foo);
  end;
aswell
  begin
dec(foo);
  end;


either 'aswell' or 'aswellas'... while foo is less than 100 increment 
foo as well as decrement foo when it is no longer less than 100...




I am not native English, but aswell to me implies "do both" and gives no 
order.
So I would expect this (the aswell block) to be executed for each 
iteration too. like the perl continue block 
http://perldoc.perl.org/functions/continue.html


btw, while I am not for it, the continue block appears much more useful 
than the "on-none-break" block. Though the continue block is not really 
ever needed, usually you can write the loop with the counter decrement 
at the top.


But the existence of such a continue block shows the fundamental issue 
on which a decision is needed. should (if a volunteer for a patch 
exists) every little "save one statement in your code helper" be added? 
Because there are thousands of them, and if you add them all the 
readability of code will go down, because you need to first learn them all.

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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Sven Barth]

Am 13.10.2015 19:21 schrieb :
>>
>> If somebody really has to do this wouldn't "also" be a better choice to
avoid
>> (getting close to overloading "as"? :-/
>
>
> it might... i don't know anything about "as" because i've never used
it... what does it do?

It's an operator for casting classes and interfaces in a safe way (which
means that an exception is raised if the cast fails).

See here:
http://www.freepascal.org/docs-html/ref/refsu47.html#x141-15100012.8.7

Regards,
Sven
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Michael Van Canneyt]

On Tue, 13 Oct 2015, Martin Frb wrote:


wkitt...@windstream.net wrote:
a... my bad... sorry 'bout that... i've been thinking about this, 
too... 'else' and 'otherwise' mean the same thing... what they seem to be 
looking for is 'aswell'...



foo := 0;
while foo < 100 do
  begin
inc(foo);
  end;
aswell
  begin
dec(foo);
  end;


either 'aswell' or 'aswellas'... while foo is less than 100 increment foo 
as well as decrement foo when it is no longer less than 100...




I am not native English, but aswell to me implies "do both" and gives no 
order.
So I would expect this (the aswell block) to be executed for each iteration 
too. like the perl continue block 
http://perldoc.perl.org/functions/continue.html


btw, while I am not for it, the continue block appears much more useful than 
the "on-none-break" block. Though the continue block is not really ever 
needed, usually you can write the loop with the counter decrement at the top.


But the existence of such a continue block shows the fundamental issue on 
which a decision is needed. should (if a volunteer for a patch exists) every 
little "save one statement in your code helper" be added? Because there are 
thousands of them, and if you add them all the readability of code will go 
down, because you need to first learn them all.


I think the answer to your question is a clear and loud "NO".

The argument that we can refrain from using these new features does not hold,
because other people will be using it, and we will have to know all of it to 
be able to understand their code.

None of these features will automagically make Object Pascal a popular language.

However, I seem to be one of the very few thinking this given the enthousiasm with 
which people are discussing this.


Soon I will be forced to emigrate to Javascript country. 
Despite all its drawbacks, it remains at least a simple language. 
a dozen keywords and you're done. No wonder Node.js is so popular.

Compare that with the jungle we're making of it... :(

Michael.
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Dmitry Boyarintsev]

On Tue, Oct 13, 2015 at 5:25 PM, Michael Van Canneyt  wrote:

> However, I seem to be one of the very few thinking this given the
> enthousiasm with which people are discussing this.
>

Even Niklaus Wirth regrets about bloating languages:
https://www.youtube.com/watch?v=BJIqHIYSDrk

thanks,
Dmitry
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Mattias Gaertner]

On Tue, 13 Oct 2015 23:25:03 +0200 (CEST)
Michael Van Canneyt  wrote:

>[...]
> The argument that we can refrain from using these new features does not hold,
> because other people will be using it, and we will have to know all of it to 
> be able to understand their code.

And it costs precious time of documentation and tool writers, who are
already lacking behind. And every new feature makes the compiler a bit
slower, costing time of all users.
Each new feature must present a solid case, why it is needed aka
outweighs the downside.


> None of these features will automagically make Object Pascal a popular 
> language.
> 
> However, I seem to be one of the very few thinking this given the enthousiasm 
> with 
> which people are discussing this.

Are you kidding?
Some people are already forking FPC because of such things.

 
> Soon I will be forced to emigrate to Javascript country. 
> Despite all its drawbacks, it remains at least a simple language. 
> a dozen keywords and you're done. No wonder Node.js is so popular.
> Compare that with the jungle we're making of it... :(

Well, then you should vote against this new functionality.


Mattias
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Sven Barth]

Am 11.10.2015 23:56 schrieb "Steve Smith" :
>
> Am I being stupid? It's late here so...
>
> What's wrong with
>
> === code begin ===
>
> while bool do
>foo;
> bar;
>
> or
>
> repeat
>foo;
> until bool;
>
> bar;
>
> === code end ===

You know... You got me there...
Though at least for the while-loop it may have a use if one defines the
then-clause as being executed only if the loop was entered once. Or - using
a different keyword - if the loop was never executed.
The repeat-loop however is always executed at least once, so there it's
completely useless indeed...

Regards,
Sven
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Sven Barth]

Am 12.10.2015 03:19 schrieb "Dmitry Boyarintsev" :
>
> a bit off-topic,
>
> But has case-otherwise been in FPC from the start?
>
> I believe it came from GNU pascal (
http://www.gnu-pascal.de/gpc/otherwise.html) and never existed in Delphi
world (
http://docwiki.embarcadero.com/RADStudio/XE3/en/Declarations_and_Statements#Case_Statements)
?!
> I can see that FPC compiles case-otherwise for any syntax mode.

It's from Extended ISO Pascal and I don't know for how long it exists in
FPC already, but it does so definitely for some time.

Regards,
Sven
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Sven Barth]

Am 12.10.2015 17:17 schrieb "Dmitry Boyarintsev" :
> About while-then. While the syntax is unlikely to break anything, it's
inconsistent with if-statement.
> where, if-then is executed when condition is true.
> For while-then is executed then condition is false.
> Thus, while-else or while-otherwise are better. However, both syntax
would cause code incompatibility.

It's less about consistency with if-then, but more about consistency from a
human language point of view.

"while true do this then that" reads more or less as well as "while true do
this otherwise that" (though both carry a slightly different meaning) with
the added benefit of the former not to break any existing code (as you had
written yourself).

Regards,
Sven
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Dmitry Boyarintsev]

On Mon, Oct 12, 2015 at 2:07 AM, Sven Barth 
wrote:

> It's from Extended ISO Pascal and I don't know for how long it exists in
> FPC already, but it does so definitely for some time.
>
Thanks! I've never thought to go and read the FP documentation on "case
statement", assuming it works in turbo pascal/delphi compatible way.

About while-then. While the syntax is unlikely to break anything, it's
inconsistent with if-statement.
where, if-then is executed when condition is true.
For while-then is executed then condition is false.
Thus, while-else or while-otherwise are better. However, both syntax would
cause code incompatibility.

thanks,
Dmitry
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Dmitry Boyarintsev]

On Mon, Oct 12, 2015 at 1:35 PM, Ralf Quint  wrote:

>
> Either the while loop is executed or it isn't, depending in the
> expression. I don't see an actual use case for any else/otherwise extension
> to it...
>

You probably want to reread python while-else implementation. (
https://docs.python.org/2/reference/compound_stmts.html)
"Else" becomes sort of "part of the loop". Thus if you break out of the
loop, "else" would not be executed.
However, if no break occurs "else" part would be executed.

It might be a rare case where it's needed. (I cannot think of any), but to
achieve exactly the same functionality in Pascal either of two options
should be used.

1) make an extra check if break occurred.

breakflag:=false;

while cond do
  if someothercond then begin
breakflag : =true;
break;
  end;

if not breakflag then
  while_else_code

2) use goto! :)

label postElseLabel

while cond do
  if someothercond then begin
 goto  postElseLabel
  end;

while_else_code
:postElseLabel

thanks,
Dmitry
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Ralf Quint]

On 10/12/2015 10:18 AM, Michael Van Canneyt wrote:


That is the meaning of "However, both syntax would cause code 
incompatibility."

and is already in my very first reply to OP.

So While... else or While .. Otherwise will never make it in the 
compiler.

Thanks for that.

This is s typical example of one of those things that just don't make 
any sense in the first place.


Either the while loop is executed or it isn't, depending in the 
expression. I don't see an actual use case for any else/otherwise 
extension to it...


Ralf

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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Ralf Quint]

On 10/12/2015 10:47 AM, Dmitry Boyarintsev wrote:


On Mon, Oct 12, 2015 at 1:35 PM, Ralf Quint > wrote:



Either the while loop is executed or it isn't, depending in the
expression. I don't see an actual use case for any else/otherwise
extension to it...


You probably want to reread python while-else implementation. 
(https://docs.python.org/2/reference/compound_stmts.html)
Sorry, we are programming here in Pascal, not Python. I could give a 
rodent's posterior about what Python implements.


People need to properly design their software, not just hacking away. 
Then they do not need to come up with whacko stop-gaps to fix what could 
have been done properly in the first place...


Ralf


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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Dmitry Boyarintsev]

On Mon, Oct 12, 2015 at 1:54 PM, Ralf Quint  wrote:

> Sorry, we are programming here in Pascal, not Python. I could give a
> rodent's posterior about what Python implements.
>
> People need to properly design their software, not just hacking away. Then
> they do not need to come up with whacko stop-gaps to fix what could have
> been done properly in the first place...
>

Well, from fpc-devel list perspective your only hope is that any new
feature is added via MODESWITCH. Thus any existing unit would be kept
clean. You would also be able to keep your libraries clean, by not allowing
using of a certain modeswitches.

However, if you look at the recent (for the past few months) discussions,
you might spot that the number of requests for new features (from recent
Delphi and other languages) is growing. Constantly.

In this particular case it's even worse (actually it's better, from
fpc-devel POV), since the patch has been provided.

The next step would probably be controlled "break", where a user would be
able to specify how many nested loops needed to broken from.

thanks,
Dmitry
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Michael Van Canneyt]

On Mon, 12 Oct 2015, Max Nazhalov wrote:



On 12.10.2015 17:17 schrieb "Dmitry Boyarintsev"  
wrote:

About while-then. While the syntax is unlikely to break anything, it's
inconsistent with if-statement.
where, if-then is executed when condition is true.
For while-then is executed then condition is false.
Thus, while-else or while-otherwise are better. However, both syntax would
cause code incompatibility.


I doubt "while-else" is a variant, due to dangling "else".

How will be compiled, e.g.
if something then
 while not_done_yet do
   the_work
else // obviously valid, and expected to be a part of "if-then-else"
 something_else_happened;


That is the meaning of "However, both syntax would cause code incompatibility."
and is already in my very first reply to OP.

So While... else or While .. Otherwise will never make it in the compiler.

Michael.
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Mark Morgan Lloyd]

Ralf Quint wrote:

On 10/12/2015 10:18 AM, Michael Van Canneyt wrote:


That is the meaning of "However, both syntax would cause code 
incompatibility."

and is already in my very first reply to OP.

So While... else or While .. Otherwise will never make it in the 
compiler.

Thanks for that.

This is s typical example of one of those things that just don't make 
any sense in the first place.


Either the while loop is executed or it isn't, depending in the 
expression. I don't see an actual use case for any else/otherwise 
extension to it...


The only possible use would be to specify a finalisation statement which 
was only executed if the while loop cycled at least once, or possibly 
one which was executed if the loop never cycled.


--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Steve Smith]

On 12/10/15 18:47, Dmitry Boyarintsev wrote:


On Mon, Oct 12, 2015 at 1:35 PM, Ralf Quint > wrote:


Either the while loop is executed or it isn't, depending in the
expression. I don't see an actual use case for any else/otherwise
extension to it...


You probably want to reread python while-else implementation.
(https://docs.python.org/2/reference/compound_stmts.html)
"Else" becomes sort of "part of the loop". Thus if you break out of the
loop, "else" would not be executed.
However, if no break occurs "else" part would be executed.

It might be a rare case where it's needed. (I cannot think of any), but to
achieve exactly the same functionality in Pascal either of two options
should be used.

1) make an extra check if break occurred.

breakflag:=false;

while cond do
   if someothercond then begin
 breakflag : =true;
 break;
   end;

if not breakflag then
   while_else_code

2) use goto! :)

label postElseLabel

while cond do
   if someothercond then begin
  goto  postElseLabel
   end;

while_else_code
:postElseLabel

thanks,
Dmitry




I can't think of a use case either. And just because another language 
provides such a solution, does not imply that FPC should. As to achieving 
the functionality in FPC:


if cond then
  while cond do
foo
else
  bar;

should suffice; Breakflags and gotos not required!
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Sven Barth]

Am 12.10.2015 20:02 schrieb "Dmitry Boyarintsev" :
>
> On Mon, Oct 12, 2015 at 1:54 PM, Ralf Quint  wrote:
>>
>> Sorry, we are programming here in Pascal, not Python. I could give a
rodent's posterior about what Python implements.
>>
>> People need to properly design their software, not just hacking away.
Then they do not need to come up with whacko stop-gaps to fix what could
have been done properly in the first place...
>
>
> Well, from fpc-devel list perspective your only hope is that any new
feature is added via MODESWITCH. Thus any existing unit would be kept
clean. You would also be able to keep your libraries clean, by not allowing
using of a certain modeswitches.

Since one point of this discussion is to implement in a way that it doesn't
break anything, it wouldn't be implemented.behind a modeswitch probably.

> However, if you look at the recent (for the past few months) discussions,
you might spot that the number of requests for new features (from recent
Delphi and other languages) is growing. Constantly.

True...

> In this particular case it's even worse (actually it's better, from
fpc-devel POV), since the patch has been provided.

However we did nowhere state that we'd incorporate the feature. I only said
that I'd definitely look at it to check whether the work in principle is
good.

> The next step would probably be controlled "break", where a user would be
able to specify how many nested loops needed to broken from.

That would be more useful than the while-else though :P

Regards,
Sven
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[wkitty42]

On 10/12/2015 01:47 PM, Dmitry Boyarintsev wrote:

On Mon, Oct 12, 2015 at 1:35 PM, Ralf Quint  wrote:

Either the while loop is executed or it isn't, depending in the expression.
I don't see an actual use case for any else/otherwise extension to it...

You probably want to reread python while-else implementation.
(https://docs.python.org/2/reference/compound_stmts.html)
"Else" becomes sort of "part of the loop". Thus if you break out of the loop,
"else" would not be executed.
However, if no break occurs "else" part would be executed.


that just doesn't make grammatical sense...

foo := 0;
while foo < 100 do
  inc(foo);
else
  dec(foo);
end


so, if foo is less than 100 we inc(foo)... if foo is not less than 100 we 
dec(foo)... that's the only way that an "else" can be read... either the boolean 
is true or /else/ it is false... only if it is false can the else portion be 
executed...


(#2) but then the question is does dec(foo) execute only once or does it execute 
as long as foo is greater than 100??


what i seem to see is pure laziness of a sort... folks too lazy to write an "if" 
or "if/else" statement and put the while inside...



foo := 0;
if foo < 100 then
  while foo < 100 do
inc(foo);
else
  dec(foo);


OR depending on the answer of (#2) above...


foo := 0;
if foo < 100 then
  while foo < 100 do
inc(foo);
  while foo > 100 do
dec(foo);


or maybe this is the actual intent?


foo := 0;
if foo < 100 then
  while foo < 100 do
inc(foo);
if foo > 100 then
  dec(foo);


seems like a pretty tough way to have foo equal to 99, eh? ;)


It might be a rare case where it's needed. (I cannot think of any), but to
achieve exactly the same functionality in Pascal either of two options should be
used.

1) make an extra check if break occurred.

[...]

2) use goto! :)


neither is needed at all in most cases and then not if they have proper logic in 
place ;)


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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Marco van de Voort]

In our previous episode, Sven Barth said:
> world (
> http://docwiki.embarcadero.com/RADStudio/XE3/en/Declarations_and_Statements#Case_Statements)
> ?!
> > I can see that FPC compiles case-otherwise for any syntax mode.
> 
> It's from Extended ISO Pascal and I don't know for how long it exists in
> FPC already, but it does so definitely for some time.

Afaik from when mode macpas was added (CodeWarrior) by Olle and Jonas.
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Max Nazhalov]

>> I can't think of a use case either. And just because another language
>> provides such a solution, does not imply that FPC should. As to achieving
>> the functionality in FPC:
>>
>> if cond then
>>while cond do
>>  foo
>> else
>>bar;
>
>That's what I've thought about from the beginning of this discussion..

The only drawback is that "cond" is calculated twice instead of once
before the actual loop body -- not all will be happy.. ;-)

-- 
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[fpc-devel] Fwd: While - Otherwise Statement

[Max Nazhalov]

> I can't think of a use case either. And just because another language
> provides such a solution, does not imply that FPC should. As to achieving
> the functionality in FPC:
>
> if cond then
>while cond do
>  foo
> else
>bar;

That's what I've thought about from the beginning of this discussion..

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Re: [fpc-devel] Fwd: While - Otherwise Statement

[wkitty42]

On 10/12/2015 02:02 PM, Dmitry Boyarintsev wrote:


The next step would probably be controlled "break", where a user would be able
to specify how many nested loops needed to broken from.


ROTFLMAO! if you need or desire something like that then set a breakcounter and 
break... in the next outer block, check breakcounter to see if you need to break 
again... if so, dec(breakcounter) and break... then check it again in the next 
outer block... and so on and so on until breakcounter=0... why should the 
compiler have to do your logic work for you? ;)


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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Dmitry Boyarintsev]

On Mon, Oct 12, 2015 at 3:11 PM,  wrote:

> On 10/12/2015 02:02 PM, Dmitry Boyarintsev wrote:
>
>>
>> The next step would probably be controlled "break", where a user would be
>> able
>> to specify how many nested loops needed to broken from.
>>
>
> ROTFLMAO! if you need or desire something like that then set a
> breakcounter and break... in the next outer block, check breakcounter to
> see if you need to break again... if so, dec(breakcounter) and break...
> then check it again in the next outer block... and so on and so on until
> breakcounter=0... why should the compiler have to do your logic work for
> you? ;)
>

How would you know if a nested loop finished properly or broke out? ...Just
imagine yourself a 4 nested for loops and you need to break out from the
4th to the 1st?

thanks,
Dmitry
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Martin Frb]

On 12/10/2015 20:01, Max Nazhalov wrote:

I can't think of a use case either. And just because another language
provides such a solution, does not imply that FPC should.

+1

(despite my earlier contribution)

Discussion of the feature below, is regardless of it not being desirable 
(in any form)



  As to achieving
the functionality in FPC:

if cond then
while cond do
  foo
else
bar;

That's what I've thought about from the beginning of this discussion..
Actually the above does not represent what the actual feature request is 
about


The "else" is to be executed, after the while (even if the while looped 
ZERO times).

But it is to be skipped if the while exited via break (and only then).

For that reason "else" or "otherwise" are badly chosen keywords. Because 
they imply a different function.




Further what is so special about the case "finishing a while loop 
without break (including 0 iterations)"?
If that case deserves special attention then surely the following also 
need (and no one should want all that)


while cond
  initialize // run before the 1st loop, if there is going to be at 
least one loop

  do  // each loop
  finalize // run after last loop, if there was at least one
  finalizeThen // run after last loop, if there was at least one // 
only if no break
  finalizeCatch // run after last loop, if there was at least one // 
only if a break happened

  then // finish, without break; or zero loops
  catch // only on break
  else // if there was no loop at all (condition was wrong, before 
first loop already)


There are all equally (none-) important. Have one have all.


Better have none.


The only drawback is that "cond" is calculated twice instead of once
before the actual loop body -- not all will be happy.. ;-)


Thats an issue for the optimizer. no need to change the language.


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Re: [fpc-devel] Fwd: While - Otherwise Statement

[wkitty42]

On 10/12/2015 03:33 PM, Dmitry Boyarintsev wrote:


On Mon, Oct 12, 2015 at 3:11 PM, > wrote:

On 10/12/2015 02:02 PM, Dmitry Boyarintsev wrote:


The next step would probably be controlled "break", where a user would
be able
to specify how many nested loops needed to broken from.


ROTFLMAO! if you need or desire something like that then set a breakcounter
and break... in the next outer block, check breakcounter to see if you need
to break again... if so, dec(breakcounter) and break... then check it again
in the next outer block... and so on and so on until breakcounter=0... why
should the compiler have to do your logic work for you? ;)


How would you know if a nested loop finished properly or broke out? ...Just
imagine yourself a 4 nested for loops and you need to break out from the 4th to
the 1st?


by checking the value that caused the break ;) deity knows i've done it many 
times before back in the TP/BP 6&7 days... i did it exactly as described, too... 
we had to do it that way as there is/was no other way to do it ;)


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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Dmitry Boyarintsev]

On Mon, Oct 12, 2015 at 3:47 PM,  wrote:

> by checking the value that caused the break ;) deity knows i've done it
> many times before back in the TP/BP 6&7 days... i did it exactly as
> described, too... we had to do it that way as there is/was no other way to
> do it ;)


That's exactly the thing. You didn't have a cross-loop break, that's why
you've to have some guaranteed values that would allow you to verify if a
loop was broken or not.

If it was broken then you'd set any additional conditions (if needed) to
break out another loop and pass it above.

In the end you end-up having additional break condition checks in each
loop. Just by the fact, that a language doesn't provide you with any other
means to do it less complex.

I'd also need to note, that no other language, to my knowledge, have
cross-loop breaks anyway :)
Good-old language (Pascal / C /C++) still have goto though... but we won't
use it, right?

thanks,
Dmitry
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Ralf Quint]

On 10/12/2015 11:33 AM, Sven Barth wrote:


Am 12.10.2015 20:02 schrieb "Dmitry Boyarintsev" 
>:

>
> On Mon, Oct 12, 2015 at 1:54 PM, Ralf Quint > wrote:

>>
>> Sorry, we are programming here in Pascal, not Python. I could give 
a rodent's posterior about what Python implements.

>>
>> People need to properly design their software, not just hacking 
away. Then they do not need to come up with whacko stop-gaps to fix 
what could have been done properly in the first place...

>
>
> Well, from fpc-devel list perspective your only hope is that any new 
feature is added via MODESWITCH. Thus any existing unit would be kept 
clean. You would also be able to keep your libraries clean, by not 
allowing using of a certain modeswitches.


Since one point of this discussion is to implement in a way that it 
doesn't break anything, it wouldn't be implemented.behind a modeswitch 
probably.


> However, if you look at the recent (for the past few months) 
discussions, you might spot that the number of requests for new 
features (from recent Delphi and other languages) is growing. Constantly.


True...

> In this particular case it's even worse (actually it's better, from 
fpc-devel POV), since the patch has been provided.


However we did nowhere state that we'd incorporate the feature. I only 
said that I'd definitely look at it to check whether the work in 
principle is good.


> The next step would probably be controlled "break", where a user 
would be able to specify how many nested loops needed to broken from.


That would be more useful than the while-else though :P


Yes, I have seen a lot of those requests and pretty much none of them 
made any sense to me. As I already stated, it always seems to me that 
someone wants to have something implemented that they have seen in a 
different language, which might have a different approach to programming 
to begin with or they "think" they need a specific feature to get them 
out of a pickle they got themselves into because they are just hacking 
away instead of properly designing their programs.
Neither of those case are IMHO valid to mess around with a working 
compiler. If someone is so fond of the features that 
Python/Haskell/Erland/jour> provides, then they should use that to solve their programming 
issues. They apparently don't understand how to use Pascal...


Ralf


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Re: [fpc-devel] Fwd: While - Otherwise Statement

[wkitty42]

On 10/12/2015 03:43 PM, Martin Frb wrote:

Actually the above does not represent what the actual feature request is about

The "else" is to be executed, after the while (even if the while looped ZERO
times).
But it is to be skipped if the while exited via break (and only then).

For that reason "else" or "otherwise" are badly chosen keywords. Because they
imply a different function.


exactly my and others' points... "and" would be better but then one might just 
as easily use a goto to jump around that part if break was used to get out of 
the loop...


anyway, it seems that no matter what the discussion, it won't make it into the 
compiler... that according to another post from a compiler dev ;)


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Re: [fpc-devel] Fwd: While - Otherwise Statement

[wkitty42]

On 10/12/2015 04:10 PM, Dmitry Boyarintsev wrote:

On Mon, Oct 12, 2015 at 3:47 PM, > wrote:

by checking the value that caused the break ;) deity knows i've done it many
times before back in the TP/BP 6&7 days... i did it exactly as described,
too... we had to do it that way as there is/was no other way to do it ;)


That's exactly the thing. You didn't have a cross-loop break, that's why you've
to have some guaranteed values that would allow you to verify if a loop was
broken or not.


yeah... i implemented my needed logic for that type of scenario... just like any 
good programmer can/will/should do...



If it was broken then you'd set any additional conditions (if needed) to break
out another loop and pass it above.

In the end you end-up having additional break condition checks in each loop.
Just by the fact, that a language doesn't provide you with any other means to do
it less complex.


ok... so instead we'll have the compiler perform my business logic for me? no 
thanks... the compiler has enough to do already ;)



I'd also need to note, that no other language, to my knowledge, have cross-loop
breaks anyway :)
Good-old language (Pascal / C /C++) still have goto though... but we won't use
it, right?


that's right... i think i may have used goto once in 30 years or however long it 
has been available in pascal... i started self-taught with basic... goto and 
gosub all over the place... tough as hades to follow the code and no apparent 
logical layout... i was ecstatic when a friend turned me on to pascal and asm... 
i dropped basic like a hot potato[e?] and never looked back... especially never 
looking back at goto ;) ;) ;)


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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Sven Barth]

Am 12.10.2015 21:43 schrieb "Martin Frb" :
>> The only drawback is that "cond" is calculated twice instead of once
>> before the actual loop body -- not all will be happy.. ;-)
>>
> Thats an issue for the optimizer. no need to change the language.

The optimizer might not be able to do anything if the expression is a
function call that can not be inlined.

Regards,
Sven
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[wkitty42]

On 10/12/2015 05:19 PM, Sven Barth wrote:

Am 12.10.2015 22:48 schrieb >:
 > anyway, it seems that no matter what the discussion, it won't make it into
the compiler... that according to another post from a compiler dev ;)

I said that I'm not sure.


it wasn't you that made that statement but if you are willing to add it, i guess 
maybe it will make it ;)



Right now I'm considering that mostly as way for the author to learn about
the ways to extend the compiler and what would be needed for a feature patch
to be accepted.


that's great! it can be a tough row to hoe learning what the proper workflow is 
when contributing to any project...



Whether this specific feature would be added or not is a different topic.


+1

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Re: [fpc-devel] Fwd: While - Otherwise Statement

[wkitty42]

On 10/12/2015 06:15 PM, David W Noon wrote:

On Mon, 12 Oct 2015 15:11:18 -0400, Wkitty42 (wkitt...@windstream.net)
wrote about "Re: [fpc-devel] Fwd: While - Otherwise Statement" (in
<561c05d6.4010...@windstream.net>):


On 10/12/2015 02:02 PM, Dmitry Boyarintsev wrote:


The next step would probably be controlled "break", where a user
would be able to specify how many nested loops needed to broken
from.


ROTFLMAO! if you need or desire something like that then set a
breakcounter and break... in the next outer block, check
breakcounter to see if you need to break again... if so,
dec(breakcounter) and break... then check it again in the next
outer block... and so on and so on until breakcounter=0... why
should the compiler have to do your logic work for you? ;)


Hi Mark,


hiya dave!! it has been a long time, my friend!!


You might have seen me write things like this in the old OS2PROG echo
of Fidonet some 20+ years ago. ... :-)


oh yeah! that echo still exists, too... but it only contains monthly moderator 
postings these days... it is ready for you any time you want to join back in... 
nntp access is available via some systems but the dawg grows older with each 
passing year :?



The only language I know that offers that level of control is PL/I,
where the break statement is coded as LEAVE.  It is handled by
labelling the loop control statement and coding the required label in
the LEAVE statement. For example:


that looks very much like what some would consider goto statements... does the 
leave return to the top of the previous loop or does it drop to the next 
statement in the previous loop?



If the label is omitted then the immediately containing loop is left.


"immediately containing loop" meaning loop_3 if we're in loop_3?


This allows any of the nested loops to be escaped, potentially all the
way out. I guess the corresponding syntax in a Pascal-esque style
would be:


that does look interesting for breaks and i can see how it may be beneficial and 
save some bit of coding but then those of us who have been around a while know 
how to work our way back out when necessary, right? ;)



If we're being strictly Pascal, the labels would need to be declared
at the head of the procedure -- and if we're really strict they should
be numeric.


yup! and i did catch the THEH->THEN oops... no problems there O:)

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Re: [fpc-devel] Fwd: While - Otherwise Statement

[David W Noon]

-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1

On Mon, 12 Oct 2015 23:15:31 +0100, David W Noon
(david.w.n...@googlemail.com) wrote about "Re: [fpc-devel] Fwd: While
- - Otherwise Statement" (in <561c3103.1060...@googlemail.com>):

[snip]
> IF some_condition THEH IF another_condition THEH IF
> some_other_condition THEH

These should all end in "THEN", not "THEH".
- -- 
Regards,

Dave  [RLU #314465]
*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
david.w.n...@googlemail.com (David W Noon)
*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*

-BEGIN PGP SIGNATURE-
Version: GnuPG v2

iEYEARECAAYFAlYcM7sACgkQogYgcI4W/5SQagCfV6i2NrBee3h76kegPVARLq5V
j7sAoNNPDGBtwsEWqdrrRiLylwoJkH7k
=ZVGL
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Flávio Etrusco]

On Mon, Oct 12, 2015 at 7:15 PM, David W Noon
<david.w.n...@googlemail.com> wrote:
> -BEGIN PGP SIGNED MESSAGE-
> Hash: SHA1
>
> On Mon, 12 Oct 2015 15:11:18 -0400, Wkitty42 (wkitt...@windstream.net)
> wrote about "Re: [fpc-devel] Fwd: While - Otherwise Statement" (in
> <561c05d6.4010...@windstream.net>):
>
>> On 10/12/2015 02:02 PM, Dmitry Boyarintsev wrote:
>>>
>>> The next step would probably be controlled "break", where a user
>>> would be able to specify how many nested loops needed to broken
>>> from.
>
> Hi Mark,
>
> You might have seen me write things like this in the old OS2PROG echo
> of Fidonet some 20+ years ago. ... :-)
>
> The only language I know that offers that level of control is PL/I,
> where the break statement is coded as LEAVE.  It is handled by
> labelling the loop control statement and coding the required label in
> the LEAVE statement. For example:
>
>loop_1: DO i = 1 TO m;
>   loop_2 : DO j = 1 TO n;
>  loop_3: DO k = 1 TO p;
>...
>IF some_condition THEH
>   LEAVE loop_3;[...]

If I'm not missing something, Java implements 'break' just like this.
I'd like such enhancement, but right now is there any reason to avoid
'goto' besides the bad karma?

Regards,
Flávio
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[David W Noon]

-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1

On Mon, 12 Oct 2015 15:11:18 -0400, Wkitty42 (wkitt...@windstream.net)
wrote about "Re: [fpc-devel] Fwd: While - Otherwise Statement" (in
<561c05d6.4010...@windstream.net>):

> On 10/12/2015 02:02 PM, Dmitry Boyarintsev wrote:
>> 
>> The next step would probably be controlled "break", where a user
>> would be able to specify how many nested loops needed to broken
>> from.
> 
> ROTFLMAO! if you need or desire something like that then set a 
> breakcounter and break... in the next outer block, check
> breakcounter to see if you need to break again... if so,
> dec(breakcounter) and break... then check it again in the next
> outer block... and so on and so on until breakcounter=0... why
> should the compiler have to do your logic work for you? ;)

Hi Mark,

You might have seen me write things like this in the old OS2PROG echo
of Fidonet some 20+ years ago. ... :-)

The only language I know that offers that level of control is PL/I,
where the break statement is coded as LEAVE.  It is handled by
labelling the loop control statement and coding the required label in
the LEAVE statement. For example:

   loop_1: DO i = 1 TO m;
  loop_2 : DO j = 1 TO n;
 loop_3: DO k = 1 TO p;
...
IF some_condition THEH
   LEAVE loop_3;
...
IF another_condition THEH
   LEAVE loop_2;
...
IF some_other_condition THEH
   LEAVE loop_1;
...
 END loop_3;
  END loop_2;
   END loop_1;

If the label is omitted then the immediately containing loop is left.

This allows any of the nested loops to be escaped, potentially all the
way out. I guess the corresponding syntax in a Pascal-esque style
would be:

   loop_1: FOR i := 1 TO m DO
   BEGIN
  loop_2: FOR j := 1 TO n DO
  BEGIN
 loop_3: FOR k := 1 TO p DO
 BEGIN
...
IF (some_condition) THEN
   BREAK loop_1;
...
IF (another_condition) THEN
   BREAK loop_2;
...
IF (some_other_condition) THEN
   BREAK loop_3;
 END
  END
   END;

If we're being strictly Pascal, the labels would need to be declared
at the head of the procedure -- and if we're really strict they should
be numeric.
- -- 
Regards,

Dave  [RLU #314465]
*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
david.w.n...@googlemail.com (David W Noon)
*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*

-BEGIN PGP SIGNATURE-
Version: GnuPG v2

iEYEARECAAYFAlYcMQMACgkQogYgcI4W/5Sl3wCgtG87fG2aCEuxkVCUrBCmxwCm
fSkAoNgXwMSNA/R4AKjDEZsNktglOqvF
=m3vh
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Sven Barth]

Am 12.10.2015 22:48 schrieb :
> anyway, it seems that no matter what the discussion, it won't make it
into the compiler... that according to another post from a compiler dev ;)

I said that I'm not sure. Right now I'm considering that mostly as way for
the author to learn about the ways to extend the compiler and what would be
needed for a feature patch to be accepted.

Whether this specific feature would be added or not is a different topic.

Regards,
Sven
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[fpc-devel] Fwd: While - Otherwise Statement

[MohsenTi]

Hi everybody

I add new feature to FPC compiler to simplify programming.
this is While - Otherwise working like While - Else in python and has
backwards compatibility.

Examples

Ex1: While (I<5) do begin Writeln(I); Dec(I); end otherwise
writeln('otherwise');

Ex2: While (I<5) do begin Writeln(I); Dec(I); break; end otherwise
writeln('otherwise');

Ex3: if (I<10) then While (I<5) do begin Writeln(I); Dec(I); break; end
otherwise writeln('otherwise') else writeln('else');

I attached a svn diff file to email and I'm going to add For-Otherwise and
more.

please test it and let me know what you think.

mohsen
Index: ncgflw.pas
===
--- ncgflw.pas  (revision 32016)
+++ ncgflw.pas  (working copy)
@@ -132,7 +132,7 @@
 
 procedure tcgwhilerepeatnode.pass_generate_code;
   var
- lcont,lbreak,lloop,
+ lcont,lbreak,lloop,lotherwise,
  oldclabel,oldblabel : tasmlabel;
  truelabel,falselabel : tasmlabel;
  oldflowcontrol : tflowcontrol;
@@ -143,6 +143,7 @@
  current_asmdata.getjumplabel(lloop);
  current_asmdata.getjumplabel(lcont);
  current_asmdata.getjumplabel(lbreak);
+ current_asmdata.getjumplabel(lotherwise);
  { arrange continue and breaklabels: }
  oldflowcontrol:=flowcontrol;
  oldclabel:=current_procinfo.CurrContinueLabel;
@@ -184,17 +185,21 @@
  hlcg.a_label(current_asmdata.CurrAsmList,lcont);
  if lnf_checknegate in loopflags then
begin
- truelabel:=lbreak;
+ truelabel:=lotherwise;
  falselabel:=lloop;
end
  else
begin
  truelabel:=lloop;
- falselabel:=lbreak;
+ falselabel:=lotherwise;
end;
  secondpass(left);
+ 
hlcg.maketojumpboollabels(current_asmdata.CurrAsmList,left,truelabel,falselabel);
+ hlcg.a_label(current_asmdata.CurrAsmList,lotherwise);
+ if (Assigned(t1)) then begin
+   secondpass(t1);
+ end;
 
- 
hlcg.maketojumpboollabels(current_asmdata.CurrAsmList,left,truelabel,falselabel);
  hlcg.a_label(current_asmdata.CurrAsmList,lbreak);
 
  sync_regvars(false);
Index: nflw.pas
===
--- nflw.pas(revision 32016)
+++ nflw.pas(working copy)
@@ -71,8 +71,11 @@
   function docompare(p: tnode): boolean; override;
end;
 
+   { twhilerepeatnode }
+
twhilerepeatnode = class(tloopnode)
   constructor create(l,r:Tnode;tab,cn:boolean);virtual;reintroduce;
+  constructor create(l,r,e:Tnode;tab,cn:boolean);virtual;reintroduce;
   function pass_typecheck:tnode;override;
   function pass_1 : tnode;override;
 {$ifdef state_tracking}
@@ -1046,7 +1049,7 @@
TWHILEREPEATNODE
 *}
 
-constructor Twhilerepeatnode.create(l,r:Tnode;tab,cn:boolean);
+constructor twhilerepeatnode.create(l, r: Tnode; tab, cn: boolean);
   begin
   inherited create(whilerepeatn,l,r,nil,nil);
   if tab then
@@ -1055,6 +1058,15 @@
   include(loopflags,lnf_checknegate);
   end;
 
+constructor twhilerepeatnode.create(l, r, e: Tnode; tab, cn: boolean);
+begin
+inherited create(whilerepeatn,l,r,e,nil);
+  if tab then
+  include(loopflags, lnf_testatbegin);
+  if cn then
+  include(loopflags,lnf_checknegate);
+end;
+
 function twhilerepeatnode.pass_typecheck:tnode;
   var
  t:Tunarynode;
Index: pstatmnt.pas
===
--- pstatmnt.pas(revision 32016)
+++ pstatmnt.pas(working copy)
@@ -328,7 +328,7 @@
 function while_statement : tnode;
 
   var
- p_e,p_a : tnode;
+ p_e,p_a,else_a : tnode;
 
   begin
  consume(_WHILE);
@@ -335,7 +335,11 @@
  p_e:=comp_expr(true,false);
  consume(_DO);
  p_a:=statement;
- result:=cwhilerepeatnode.create(p_e,p_a,true,false);
+ if (try_to_consume(_OTHERWISE)) then
+  else_a := statement
+ else
+  else_a := nil;
+Result := cwhilerepeatnode.Create(p_e, p_a, else_a, True, False);
   end;
 
 { a helper function which is used both by "with" and "for-in loop" nodes }
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Sven Barth]

Am 11.10.2015 15:56 schrieb "MohsenTi" :
>
> Hi everybody
>
> I add new feature to FPC compiler to simplify programming.
> this is While - Otherwise working like While - Else in python and has
backwards compatibility.

Nice idea with the otherwise. I first thought that this would break
case-statements that use otherwise instead of else, but then I remembered
that the case-label-blocks can and IMHO should be terminated by ; anyway.
At least problems can be easily circumvented.

I don't know whether we'll add it to trunk, but I'll at least take a look
at your code to give you feedback.

Oh, and please provide simple tests for your feature that could be added to
our testsuite (in tests/test or tests/tbs) in case we decide to incorporate
it.
Speaking of which: did you run the testsuite and compared the results to a
run without modifications?
(If you need help with running the testsuite or interpreting the results,
please ask, I have yet to write a wiki page for that...)

Regards,
Sven
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[MohsenTi]

I create 2 test files depends on testsuite readme file and make testsuite
with make full command and set TEST_FPC variable to fpc ppcx64 compiler.

for-otherwise and while-otherwise diff file and test files attached to
email.

test result :

Total = 6906 (75:6831)
Total number of compilations = 4264 (60:4204)
Successfully compiled = 3147
Successfully failed = 1057
Compilation failures = 55
Compilation that did not fail while they should = 5
Total number of runs = 2642 (15:2627)
Successful runs = 2627
Failed runs = 15
Number units compiled = 135
Number program that should not be run = 367
Number of skipped tests = 404
Number of skipped graph tests = 10
Number of skipped interactive tests = 31
Number of skipped known bug tests = 6
Number of skipped tests for other versions = 4
Number of skipped tests for other cpus = 190
Number of skipped tests for other targets = 163

I checked failed ones but it seems they are not related to my changes.
What you think?

thanks a lot


On Sun, Oct 11, 2015 at 6:44 PM, Sven Barth 
wrote:

> Am 11.10.2015 15:56 schrieb "MohsenTi" :
> >
> > Hi everybody
> >
> > I add new feature to FPC compiler to simplify programming.
> > this is While - Otherwise working like While - Else in python and has
> backwards compatibility.
>
> Nice idea with the otherwise. I first thought that this would break
> case-statements that use otherwise instead of else, but then I remembered
> that the case-label-blocks can and IMHO should be terminated by ; anyway.
> At least problems can be easily circumvented.
>
> I don't know whether we'll add it to trunk, but I'll at least take a look
> at your code to give you feedback.
>
> Oh, and please provide simple tests for your feature that could be added
> to our testsuite (in tests/test or tests/tbs) in case we decide to
> incorporate it.
> Speaking of which: did you run the testsuite and compared the results to a
> run without modifications?
> (If you need help with running the testsuite or interpreting the results,
> please ask, I have yet to write a wiki page for that...)
>
> Regards,
> Sven
>
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>
>
Index: ncgflw.pas
===
--- ncgflw.pas  (revision 32016)
+++ ncgflw.pas  (working copy)
@@ -132,7 +132,7 @@
 
 procedure tcgwhilerepeatnode.pass_generate_code;
   var
- lcont,lbreak,lloop,
+ lcont,lbreak,lloop,lotherwise,
  oldclabel,oldblabel : tasmlabel;
  truelabel,falselabel : tasmlabel;
  oldflowcontrol : tflowcontrol;
@@ -143,6 +143,7 @@
  current_asmdata.getjumplabel(lloop);
  current_asmdata.getjumplabel(lcont);
  current_asmdata.getjumplabel(lbreak);
+ current_asmdata.getjumplabel(lotherwise);
  { arrange continue and breaklabels: }
  oldflowcontrol:=flowcontrol;
  oldclabel:=current_procinfo.CurrContinueLabel;
@@ -184,17 +185,21 @@
  hlcg.a_label(current_asmdata.CurrAsmList,lcont);
  if lnf_checknegate in loopflags then
begin
- truelabel:=lbreak;
+ truelabel:=lotherwise;
  falselabel:=lloop;
end
  else
begin
  truelabel:=lloop;
- falselabel:=lbreak;
+ falselabel:=lotherwise;
end;
  secondpass(left);
+ 
hlcg.maketojumpboollabels(current_asmdata.CurrAsmList,left,truelabel,falselabel);
+ hlcg.a_label(current_asmdata.CurrAsmList,lotherwise);
+ if (Assigned(t1)) then begin
+   secondpass(t1);
+ end;
 
- 
hlcg.maketojumpboollabels(current_asmdata.CurrAsmList,left,truelabel,falselabel);
  hlcg.a_label(current_asmdata.CurrAsmList,lbreak);
 
  sync_regvars(false);
@@ -413,7 +418,7 @@
 
 procedure tcgfornode.pass_generate_code;
   var
- l3,oldclabel,oldblabel : tasmlabel;
+ l3,lotherwise,oldclabel,oldblabel : tasmlabel;
  temptovalue : boolean;
  hop : topcg;
  hcond : topcmp;
@@ -430,7 +435,7 @@
  current_asmdata.getjumplabel(current_procinfo.CurrContinueLabel);
  current_asmdata.getjumplabel(current_procinfo.CurrBreakLabel);
  current_asmdata.getjumplabel(l3);
-
+ current_asmdata.getjumplabel(lotherwise);
  { only calculate reference }
  opsize := def_cgsize(left.resultdef);
  count_var_is_signed:=is_signed(left.resultdef);
@@ -794,6 +799,16 @@
tcgint(cmp_const.svalue),left.location,l3);
end;
 
+   hlcg.a_label(current_asmdata.CurrAsmList,lotherwise);
+
+   if (Assigned(e)) then
+   begin
+ oldexecutionweight:=cg.executionweight;
+ cg.executionweight:=cg.executionweight*8;
+ 

Re: [fpc-devel] Fwd: While - Otherwise Statement

[Martin Frb]

On 11/10/2015 16:14, Sven Barth wrote:


Am 11.10.2015 15:56 schrieb "MohsenTi" >:

>
> Hi everybody
>
> I add new feature to FPC compiler to simplify programming.
> this is While - Otherwise working like While - Else in python and 
has backwards compatibility.


Nice idea with the otherwise. I first thought that this would break 
case-statements that use otherwise instead of else, but then I 
remembered that the case-label-blocks can and IMHO should be 
terminated by ; anyway. At least problems can be easily circumvented.


"should", but they do not have to, at least not the last one before the 
otherwise


So if old code has

  case a of
1 : write;
2:  while a > 1 do a := a -1
otherwise
write;
end

that will break. (it can be fixed, but so could the if with while else.

why not a new keyword?

while bool do
  foo()
afterwards [do]  // or even "then" would make sense (from english 
reading perspective)

  bar();





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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Martin Frb]

On 11/10/2015 22:33, Tomas Hajny wrote:

On Sun, October 11, 2015 22:48, Sven Barth wrote:
  .
  .

That "then" is a great idea! That would definitely not break anything and
it would make sense indeed:

=== code begin ===
while bool do
   foo
then
   bar;

repeat
   foo;
until bool then
   bar;
=== code end ===

I'm afraid that I got lost in this discussion, but what exactly would be
the supposed semantic difference between the behaviour compared to
situation when there was a semicolon instead of 'then' there?


You mean compared to the otherwise solution?

The following is currently valid code:
case a of
  1: write;
  2: while a > 0 do dec(a)   // no semicolon
  otherwise
 write('a was neither 1 nor 2');
end;

This code would continue to compile, but it would change meaning/behaviour.
So if somebody has code like that, in a million line project, which 
fails after otherwise was introduced, then it could be a long search for 
why it fails. (Easy to fix once found, but hard to find)


Besides "then" makes more sense (as in reading it as english description).

Both else/otherwise, to me read as: If the while block before was not 
executed at all.

In otherwords
  while a > 0 do write
  otherwise halt;
reads to me "halt" is an alternative to the "while". It gets executed if 
the while was never executde (a was already <= 0 when while was reached 
first)


"then" in english may mean "after that" and that is what happens here. 
After the while do something.

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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Sven Barth]

Am 11.10.2015 18:56 schrieb "MohsenTi" :
> I checked failed ones but it seems they are not related to my changes.

It's best you compare the faillist files in tests/output/cpu-os from an
unmodified and a modified run. This way you can find out if you had any
changes in the testsuite.

Also the testfiles /must/ start with a "t". I haven't yet looked at the
code though (I'm a bit busy otherwise so it will take some time for me).

Regards,
Sven
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Sven Barth]

Am 11.10.2015 18:34 schrieb "Martin Frb" :
>
> On 11/10/2015 16:14, Sven Barth wrote:
>>
>> Am 11.10.2015 15:56 schrieb "MohsenTi" :
>> >
>> > Hi everybody
>> >
>> > I add new feature to FPC compiler to simplify programming.
>> > this is While - Otherwise working like While - Else in python and has
backwards compatibility.
>>
>> Nice idea with the otherwise. I first thought that this would break
case-statements that use otherwise instead of else, but then I remembered
that the case-label-blocks can and IMHO should be terminated by ; anyway.
At least problems can be easily circumvented.
>
> "should", but they do not have to, at least not the last one before the
otherwise

I know and that's something I'm probably going to be wondering about for
all eternity -.-

> why not a new keyword?

I'm not a fan of adding new keywords for something like this...

> while bool do
>   foo()
> afterwards [do]  // or even "then" would make sense (from english reading
perspective)
>   bar();

That "then" is a great idea! That would definitely not break anything and
it would make sense indeed:

=== code begin ===

while bool do
  foo
then
  bar;

repeat
  foo;
until bool then
  bar;

=== code end ===

Regards,
Sven
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Tomas Hajny]

On Sun, October 11, 2015 22:48, Sven Barth wrote:
 .
 .
> That "then" is a great idea! That would definitely not break anything and
> it would make sense indeed:
>
> === code begin ===
> while bool do
>   foo
> then
>   bar;
>
> repeat
>   foo;
> until bool then
>   bar;
> === code end ===

I'm afraid that I got lost in this discussion, but what exactly would be
the supposed semantic difference between the behaviour compared to
situation when there was a semicolon instead of 'then' there?

Tomas


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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Steve Smith]

On 11/10/15 21:48, Sven Barth wrote:


That "then" is a great idea! That would definitely not break anything and it
would make sense indeed:

=== code begin ===

while bool do
   foo
then
   bar;

repeat
   foo;
until bool then
   bar;

=== code end ===

Regards,
Sven


Am I being stupid? It's late here so...

What's wrong with
=== code begin ===

while bool do
   foo;
bar;

or

repeat
   foo;
until bool;
bar;

=== code end ===
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Steve Smith]

On 11/10/15 22:52, Steve Smith wrote:

On 11/10/15 21:48, Sven Barth wrote:


That "then" is a great idea! That would definitely not break anything and it
would make sense indeed:

=== code begin ===

while bool do
   foo
then
   bar;

repeat
   foo;
until bool then
   bar;

=== code end ===

Regards,
Sven


Am I being stupid? It's late here so...

What's wrong with
=== code begin ===

while bool do
foo;
bar;

or

repeat
foo;
until bool;
bar;

=== code end ===
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Oops... Sorry Tomas!
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Re: [fpc-devel] Fwd: While - Otherwise Statement

[Dmitry Boyarintsev]

a bit off-topic,

But has case-otherwise been in FPC from the start?

I believe it came from GNU pascal (
http://www.gnu-pascal.de/gpc/otherwise.html) and never existed in Delphi
world (
http://docwiki.embarcadero.com/RADStudio/XE3/en/Declarations_and_Statements#Case_Statements)
?!
I can see that FPC compiles case-otherwise for any syntax mode.

thanks,
Dmitry
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