Re: exit case body/prog/function

[dean]

Hi John
Yes...you're right...I was using an (if (or (stop test 1) (stop test 2))
(do nothing) (do all the stuff)
but your "unless" is much more direct.
Hi Alex
Yes I like that a lot!
Thank you both for your further help.
Best Regards
Dean

On 19 January 2017 at 17:02, Alexander Burger  wrote:

> On Thu, Jan 19, 2017 at 05:50:00PM +0100, Alexander Burger wrote:
> > Note that (setq Do_it NIL) is (off Do_it), and you could also use an
> 'or' for
> > the two equal consequences. Then the above becomes:
> >
> >(setq
> >   Pg_bks 7
> >   Lns_from_top 6
> >   Do_it T )
> >(case 2
> >   (1 (prinl "in 1"))
> >   (2
> >  (cond
> > ((or (> 2 Pg_blks) (> 6 Lns_from_top))
> >(off Do_it) )
> > (Do_it
> >(prinl "yes doing a")
> >(prinl "yes doing b")
> >(prinl "yes doing c") ) ) ) )
>
>
> Normally, of course, you will use 'let' instead of 'setq':
>
>(let (Pg_bks 7  Lns_from_top 6  Do_it T)
>   (case 2
>  (1 (prinl "in 1"))
>  (2
> (cond
>((or (> 2 Pg_blks) (> 6 Lns_from_top))
>   (off Do_it) )
>(Do_it
>   (prinl "yes doing a")
>   (prinl "yes doing b")
>   (prinl "yes doing c") ) ) ) ) )
>
> ♪♫ Alex
> --
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>

Re: exit case body/prog/function

[Alexander Burger]

On Thu, Jan 19, 2017 at 05:50:00PM +0100, Alexander Burger wrote:
> Note that (setq Do_it NIL) is (off Do_it), and you could also use an 'or' for
> the two equal consequences. Then the above becomes:
> 
>(setq
>   Pg_bks 7
>   Lns_from_top 6
>   Do_it T )
>(case 2
>   (1 (prinl "in 1"))
>   (2
>  (cond
> ((or (> 2 Pg_blks) (> 6 Lns_from_top))
>(off Do_it) )
> (Do_it
>(prinl "yes doing a")
>(prinl "yes doing b")
>(prinl "yes doing c") ) ) ) )


Normally, of course, you will use 'let' instead of 'setq':

   (let (Pg_bks 7  Lns_from_top 6  Do_it T)
  (case 2
 (1 (prinl "in 1"))
 (2
(cond
   ((or (> 2 Pg_blks) (> 6 Lns_from_top))
  (off Do_it) )
   (Do_it
  (prinl "yes doing a")
  (prinl "yes doing b")
  (prinl "yes doing c") ) ) ) ) )

♪♫ Alex
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Re: exit case body/prog/function

[Alexander Burger]

Hi Dean,

> (setq Pg_bks 7)
> (setq Lns_from_top 6)
> (setq Do_it T)
> (case 2
>(1 (prinl "in 1"))
>(2
>   (if (> 2 Pg_blks)  (setq Do_it NIL))
>   (if (> 6 Lns_from_top) (setq Do_it NIL))
>   (if (Do_it) (prinl "yes doing a"))
>   (if (Do_it) (prinl "yes doing b"))
>   (if (Do_it) (prinl "yes doing c")))
> 
> 
> I'm really after this.
> I like it because of the very flat structure, I can write the "stop" rules
> in a very natural way and One objection stops any further execution. I have
> had some very experienced programmers comment that this style is
> uglyMaybe but I find it very easy to understand/maintain.
> 
> #fn some_fn   or in lisp (prog..)
> #   if cond1 then exit fn
> #   if cond2 then exit fn
> #   do a
> #   do b
> #   do c
> #end fn

This is a typical 'cond' case

   (cond
  ((> 2 Pg_blks) (setq Do_it NIL))
  ((> 6 Lns_from_top) (setq Do_it NIL))
  (Do_it
 (prinl "yes doing a")
 (prinl "yes doing b")
 (prinl "yes doing c") ) )


Note that (setq Do_it NIL) is (off Do_it), and you could also use an 'or' for
the two equal consequences. Then the above becomes:

   (setq
  Pg_bks 7
  Lns_from_top 6
  Do_it T )
   (case 2
  (1 (prinl "in 1"))
  (2
 (cond
((or (> 2 Pg_blks) (> 6 Lns_from_top))
   (off Do_it) )
(Do_it
   (prinl "yes doing a")
   (prinl "yes doing b")
   (prinl "yes doing c") ) ) ) )

♪♫ Alex
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Re: exit case body/prog/function

[dean]

Hi Alex
Thank you for confirming no return and the alternative.
Best Regards
Dean

On 19 January 2017 at 14:44, Alexander Burger  wrote:

> Hi Dean,
>
> > I'd like to do this but am not sure if it's possible
> >
> > ( case 
> >#= start of match clause
> >(
> >(prog
> >(if () (EXIT THIS MATCH CLAUSE/PROG))
> >(otherwise you'll execute this statement)
> >)
> >   )
> >   #= end of match clause
> >   .
> >   .
> >   .
> > I also wonder if there's a similar... (if (T) (EXIT FUNCTION))
>
> If I understand you right, you are looking for an exit out of a nested
> expression, like a 'return' statment in C or Java.
>
> Such a return does not exist, there is catch/throw for that
>
>(catch 'something
>   (for (..)
>  (if (..)
> (throw 'something)
> (elseStuff)
> ..
>
> Catch/throw is more general then 'return', but the latter can be emulated
> with
> it.
>
> ♪♫ Alex
> --
> UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
>

Re: exit case body/prog/function

[Alexander Burger]

Hi Dean,

> I'd like to do this but am not sure if it's possible
> 
> ( case 
>#= start of match clause
>(
>(prog
>(if () (EXIT THIS MATCH CLAUSE/PROG))
>(otherwise you'll execute this statement)
>)
>   )
>   #= end of match clause
>   .
>   .
>   .
> I also wonder if there's a similar... (if (T) (EXIT FUNCTION))

If I understand you right, you are looking for an exit out of a nested
expression, like a 'return' statment in C or Java.

Such a return does not exist, there is catch/throw for that

   (catch 'something
  (for (..)
 (if (..)
(throw 'something)
(elseStuff)
..

Catch/throw is more general then 'return', but the latter can be emulated with
it.

♪♫ Alex
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Re: exit case body/prog/function

[dean]

Ok here we are...
This is the nearest I can get in PL with my limited familarity i.e. a very
flat structure

(setq Pg_bks 7)
(setq Lns_from_top 6)
(setq Do_it T)
(case 2
   (1 (prinl "in 1"))
   (2
  (if (> 2 Pg_blks)  (setq Do_it NIL))
  (if (> 6 Lns_from_top) (setq Do_it NIL))
  (if (Do_it) (prinl "yes doing a"))
  (if (Do_it) (prinl "yes doing b"))
  (if (Do_it) (prinl "yes doing c")))


I'm really after this.
I like it because of the very flat structure, I can write the "stop" rules
in a very natural way and One objection stops any further execution. I have
had some very experienced programmers comment that this style is
uglyMaybe but I find it very easy to understand/maintain.

#fn some_fn   or in lisp (prog..)
#   if cond1 then exit fn
#   if cond2 then exit fn
#   do a
#   do b
#   do c
#end fn

On 19 January 2017 at 14:01, dean  wrote:

> Thank you very much Joe.,,,I see what you mean and don't think I've been
> clear enough.
> I'll try and put a better example together.
> It might be because of Lisps "everything returns a value" my constructs
> aren't compatible.
> We'll seeback soon.
>
> On 19 January 2017 at 13:13, Joe Bogner  wrote:
>
>> dean, I would use unless.
>>
>> See this control structure below as an alternative to the prog/if
>>
>> : (setq Test1 1)
>> -> 1
>> : (case Test1 (1 (unless Test2 (prinl "true"
>> true
>> -> "true"
>>
>> : (setq Test2 "Nope")
>> -> "Nope"
>> : (case Test1 (1 (unless Test2 (prinl "true"
>> -> NIL
>>
>>
>>
>> On Thu, Jan 19, 2017 at 7:55 AM, dean  wrote:
>>
>>> I'd like to do this but am not sure if it's possible
>>>
>>> ( case 
>>>#= start of match clause
>>>(
>>>(prog
>>>(if () (EXIT THIS MATCH CLAUSE/PROG))
>>>(otherwise you'll execute this statement)
>>>)
>>>   )
>>>   #= end of match clause
>>>   .
>>>   .
>>>   .
>>> I also wonder if there's a similar... (if (T) (EXIT FUNCTION))
>>>
>>
>>
>

Re: exit case body/prog/function

[dean]

Thank you very much Joe.,,,I see what you mean and don't think I've been
clear enough.
I'll try and put a better example together.
It might be because of Lisps "everything returns a value" my constructs
aren't compatible.
We'll seeback soon.

On 19 January 2017 at 13:13, Joe Bogner  wrote:

> dean, I would use unless.
>
> See this control structure below as an alternative to the prog/if
>
> : (setq Test1 1)
> -> 1
> : (case Test1 (1 (unless Test2 (prinl "true"
> true
> -> "true"
>
> : (setq Test2 "Nope")
> -> "Nope"
> : (case Test1 (1 (unless Test2 (prinl "true"
> -> NIL
>
>
>
> On Thu, Jan 19, 2017 at 7:55 AM, dean  wrote:
>
>> I'd like to do this but am not sure if it's possible
>>
>> ( case 
>>#= start of match clause
>>(
>>(prog
>>(if () (EXIT THIS MATCH CLAUSE/PROG))
>>(otherwise you'll execute this statement)
>>)
>>   )
>>   #= end of match clause
>>   .
>>   .
>>   .
>> I also wonder if there's a similar... (if (T) (EXIT FUNCTION))
>>
>
>

Re: exit case body/prog/function

[Joe Bogner]

dean, I would use unless.

See this control structure below as an alternative to the prog/if

: (setq Test1 1)
-> 1
: (case Test1 (1 (unless Test2 (prinl "true"
true
-> "true"

: (setq Test2 "Nope")
-> "Nope"
: (case Test1 (1 (unless Test2 (prinl "true"
-> NIL



On Thu, Jan 19, 2017 at 7:55 AM, dean  wrote:

> I'd like to do this but am not sure if it's possible
>
> ( case 
>#= start of match clause
>(
>(prog
>(if () (EXIT THIS MATCH CLAUSE/PROG))
>(otherwise you'll execute this statement)
>)
>   )
>   #= end of match clause
>   .
>   .
>   .
> I also wonder if there's a similar... (if (T) (EXIT FUNCTION))
>

exit case body/prog/function

[dean]

I'd like to do this but am not sure if it's possible

( case 
   #= start of match clause
   (
   (prog
   (if () (EXIT THIS MATCH CLAUSE/PROG))
   (otherwise you'll execute this statement)
   )
  )
  #= end of match clause
  .
  .
  .
I also wonder if there's a similar... (if (T) (EXIT FUNCTION))