Re: [fpc-pascal] Freepascal Floating Point Issue

2017-08-21 Thread bernd.oppol...@t-online.de 

https://www.facebook.com/notes/new-stanford-pascal-compiler/floating-point-output-differences-between-platforms/365845753799072

 
/

other Pascal Implementations have to provide solutions to this issue, too

Kind regards

Bernd




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--- Original-Nachricht ---
Von: Sven Barth via fpc-pascal
Betreff: Re: [fpc-pascal] Freepascal Floating Point Issue
Datum: 22.08.2017, 7:54 Uhr
An: FPC-Pascal users discussions
Cc: Sven Barth



Am 22.08.2017 00:02 schrieb "James Richters" <
ja...@productionautomation.net  >:

The others already wrote about floating point precision, so I won't repeat 
that.

> The reason I noticed this is because I have some conditional statements 
like
> If Draw_GX_Min<>99.999 then
> Something

*DON'T* compare floating point numbers like that. Instead use SameValue() 
from the Math unit which has an additional epsilon value (with a default 
value) that defines a lower and upper bound from your desired value to 
compare to.

Regards,
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Re: [fpc-pascal] H2pas tool vs others, C header translation

2017-08-21 Thread noreply 

On 2017-08-21 20:34, Dmitry Boyarintsev wrote:

On Sun, Aug 20, 2017 at 5:37 PM,  wrote:


Is there a competing tool that does more, or is updated more?


How about this list?
http://wiki.freepascal.org/C_to_Pascal


That's a good one, I missed that.. could not find it previously when 
searching google


Did you write CHelper because H2pas was not to your satisfaction?
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Re: [fpc-pascal] Freepascal Floating Point Issue

2017-08-21 Thread Sven Barth via fpc-pascal 
Am 22.08.2017 00:02 schrieb "James Richters" :

The others already wrote about floating point precision, so I won't repeat
that.

> The reason I noticed this is because I have some conditional statements
like
> If Draw_GX_Min<>99.999 then
> Something

*DON'T* compare floating point numbers like that. Instead use SameValue()
from the Math unit which has an additional epsilon value (with a default
value) that defines a lower and upper bound from your desired value to
compare to.

Regards,
Sven
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Re: [fpc-pascal] H2pas tool vs others, C header translation

2017-08-21 Thread Dmitry Boyarintsev 
On Sun, Aug 20, 2017 at 5:37 PM,  wrote:

>
> Is there a competing tool that does more, or is updated more?
>

How about this list?
http://wiki.freepascal.org/C_to_Pascal
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Re: [fpc-pascal] H2pas tool vs others, C header translation

2017-08-21 Thread Dmitry Boyarintsev 
On Sun, Aug 20, 2017 at 5:37 PM,  wrote:

> Is h2pas for example the one that is used for Mysql header translations
> and other major C headers?
>

I'm using Chelper.  (http://wiki.freepascal.org/Chelper)
It's my choice, because it preserves comments (which is usually an
important part of open-source libs)
plus, can be configured to handle library header-specific defines.
Naturally, the process is semi-automatic, but get be done quite quickly.


> I am looking to convert the GNU MPFR library header files, or hire someone
> on a bounty to do it if header translation is not so easy with h2pas and
> requires lots of hand work, and close checking.
>

Speaking of bounties.
There was a bounty (http://wiki.freepascal.org/Bounties#Linux_bounties) for
converting libwebsockets to fpc.
I took it and did the conversion using Chelper.
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Re: [fpc-pascal] Freepascal Floating Point Issue

2017-08-21 Thread Daniel Franzini 
Long story short: not every single real number have an *exact*
representation in the computer. You have to live with that and learn the
limitations and pitfalls of floating point calculations.

On Mon, Aug 21, 2017 at 7:42 PM, Ralf Quint  wrote:

> On 8/21/2017 3:34 PM, Daniel Franzini wrote:
> > It might be the case (I didn't do the math) that 999.999 doesn't have
> > an exact representation in IEEE-754 double-precision format, so the
> > best you get is an aproximation (a pretty good one, btw).
> Just use WriteLn (Draw_GX_Min:3:16) and you get no mystery digits
> anymore...
>
> In pretty much any programming language/compiler, if you print more
> digits than the precision of the used variable defines, you will get
> random numbers after the defined precision.
> This is not something FreePascal specific, any C/C++ compiler for
> example will do the same thing. People need to learn what limitations
> come along with floating point variables/calculations...
>
> Ralf
>
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-- 
Daniel

"Let us change our traditional attitude to the construction of programs.
Instead of imagining that our main task is to instruct a computer what to
do, let us concentrate rather on explaining to human beings what we want a
computer to do." (Donald Knuth)

"Yes, technogeeks can be funny, even if only to each other." (
http://www.boogieonline.com/revolution/science/humor/)"

"Man is driven to create; I know I really love to create things. And while
I'm not good at painting, drawing, or music, I can write software."
(Yukihiro Matsumoto, a.k.a. ``Matz'')
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Re: [fpc-pascal] Freepascal Floating Point Issue

2017-08-21 Thread Ralf Quint 
On 8/21/2017 3:34 PM, Daniel Franzini wrote:
> It might be the case (I didn't do the math) that 999.999 doesn't have
> an exact representation in IEEE-754 double-precision format, so the
> best you get is an aproximation (a pretty good one, btw).
Just use WriteLn (Draw_GX_Min:3:16) and you get no mystery digits anymore...

In pretty much any programming language/compiler, if you print more
digits than the precision of the used variable defines, you will get
random numbers after the defined precision.
This is not something FreePascal specific, any C/C++ compiler for
example will do the same thing. People need to learn what limitations
come along with floating point variables/calculations...

Ralf

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Re: [fpc-pascal] Freepascal Floating Point Issue

2017-08-21 Thread Daniel Franzini 
It might be the case (I didn't do the math) that 999.999 doesn't have an
exact representation in IEEE-754 double-precision format, so the best you
get is an aproximation (a pretty good one, btw).

On Mon, Aug 21, 2017 at 7:10 PM, Ralf Quint  wrote:

> On 8/21/2017 3:02 PM, James Richters wrote:
> > I am having an issue with a simple floating point application.  I am
> setting a variable to a specific value and immediately after I set it,  it
> is not exactly what I set it to.  Here's an example
> >
> >Draw_GX_Min:=999.999;
> >Writeln(Draw_GX_Min:3:30);
> >
> > The writeln results in 999.999002
> >
> > Why is it not  999.999000  where did
> 0.02 come from?
> >
> Out of thin air... Well, kind of. Double floating point means 16 digits
> of precision, so when you force a 30 digit precision output, anything
> past 16 digits is random garbage, at best...
>
> Ralf
>
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-- 
Daniel

"Let us change our traditional attitude to the construction of programs.
Instead of imagining that our main task is to instruct a computer what to
do, let us concentrate rather on explaining to human beings what we want a
computer to do." (Donald Knuth)

"Yes, technogeeks can be funny, even if only to each other." (
http://www.boogieonline.com/revolution/science/humor/)"

"Man is driven to create; I know I really love to create things. And while
I'm not good at painting, drawing, or music, I can write software."
(Yukihiro Matsumoto, a.k.a. ``Matz'')
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Re: [fpc-pascal] Freepascal Floating Point Issue

2017-08-21 Thread Ralf Quint 
On 8/21/2017 3:02 PM, James Richters wrote:
> I am having an issue with a simple floating point application.  I am setting 
> a variable to a specific value and immediately after I set it,  it is not 
> exactly what I set it to.  Here's an example
>
>Draw_GX_Min:=999.999;
>Writeln(Draw_GX_Min:3:30);
>
> The writeln results in 999.999002  
>
> Why is it not  999.999000  where did 0.02 
> come from?
>
Out of thin air... Well, kind of. Double floating point means 16 digits
of precision, so when you force a 30 digit precision output, anything
past 16 digits is random garbage, at best...

Ralf

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[fpc-pascal] Freepascal Floating Point Issue

2017-08-21 Thread James Richters 
I am having an issue with a simple floating point application.  I am setting a 
variable to a specific value and immediately after I set it,  it is not exactly 
what I set it to.  Here's an example

   Draw_GX_Min:=999.999;
   Writeln(Draw_GX_Min:3:30);

The writeln results in 999.999002  

Why is it not  999.999000  where did 0.02 
come from?

Draw_GX_Min is defined as a Double.  I don't need that much precision for any 
reason.   I'm just trying to understand why it's not what I set it to.

The reason I noticed this is because I have some conditional statements like
If Draw_GX_Min<>99.999 then
Something 

And sometimes they works as expected, and sometimes not.
I realize I could do:

If round(Draw_GX_Min*1000)<>99 then
   Something 

and it would work, but why do I need to do this when I explicitly set it to 
999.999?

Does anyone know what is going on here that would be kind enough to explain it 
to me?

I suspect this has something to do with floating point, but I don't really 
understand what's happening.

Is there a better way to define my variable, perhaps defined as fixed decimal 
point instead of allowing it to float  so that say all numbers from 
-999.9 to 999.9 are guaranteed to be represented accurately to 5 
decimal places so that if I set one to 999.9 it would actually be 999.9 
exactly?  I would rather have less precision but have variables retain exactly 
what they are set to, not something close

Thanks

James




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Re: [fpc-pascal] fpReport released

2017-08-21 Thread leledumbo via fpc-pascal 
> fpreport has been committed to FPC SVN: packages/fcl-report. 
> It should compile on windows, linux, freebsd and darwin.

From the wiki:
"An important use-case was a Linux server running in a container without X
libraries installed"

Yep, yep, yep. Finally I can replace my old statically designed reports :)



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Re: [fpc-pascal] H2pas tool vs others, C header translation

2017-08-21 Thread Marco van de Voort 
In our previous episode, Michael Van Canneyt said:
> > I am looking to convert the GNU MPFR library header files, or hire 
> > someone on a bounty to do it if header translation is not so easy with 
> > h2pas and requires lots of hand work, and close checking.
> 
> I do all header translations with h2pas. Most of the time, I run the code
> first through gcc -E, which will take care of all macro magic. Usually h2pas
> has little trouble with the result.

Before everything I do a couple of substs with an editor, then instead of
gcc -E I use small pascal filterprograms to sort the symbols based on
heuristics.  Usually "clean" defines, structs, function calls and "rest".

The clear files I translate by h2pas, the rest manually or with pascal
programs, and then I stitch them together again. I try to preserve comments
as much as possible.

In the past, with very large headers, I did this restitching
semiautomatically, by inserting marker comments while splitting.

I tried all other headerconvertors, and didn't have a better result.
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[fpc-pascal] StringOfChar for Unicode/Widestring

2017-08-21 Thread Bart 
Hi,

Do we  have a StringOfChar function for UnicodeString/WideString in FreePascal?
I could not find it in 3.0.4RC1 (which may tell you more about me that fpc).

Bart
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Re: [fpc-pascal] TStringHelper missing

2017-08-21 Thread Sven Barth via fpc-pascal 
Am 21.08.2017 13:51 schrieb "Sven Barth" :
>
> Am 21.08.2017 08:23 schrieb "Michael Van Canneyt" :
> >
> >
> >
> > On Mon, 21 Aug 2017, Ryan Joseph wrote:
> >
> >> I’m trying to split a string by a delimiter and see there is a type
helper called TStringHelper (
https://www.freepascal.org/docs-html/rtl/sysutils/tstringhelper.html). The
compiler version I’m using is "Free Pascal Compiler version 3.1.1
[2017/04/22] for i386” but when I include SysUtils the methods are not
found.
> >>
> >> For example:
> >>
> >> var
> >>  str: string;
> >>  parts: TStringArray;
> >>
> >> parts := str.Split(' ‘);
> >>
> >>
> >> What am I doing wrong?
> >
> >
> > Try
> >
> > var
> >   Str : AnsiString;
> > or
> >   Str : WideString;
> >
> > I believe the compiler has some trouble finding the helper if you use
the
> > 'string' alias. I think there is even a bugreport about it.
> > Sven Barth can confirm/deny this.
>
> I thought that was fixed? Except of course if $H- is used (which is the
default in all modes except the Delphi ones) cause then String = AnsiString.

String = ShortString in case of $H- of course -.-

Regards,
Sven
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Re: [fpc-pascal] TStringHelper missing

2017-08-21 Thread Sven Barth via fpc-pascal 
Am 21.08.2017 08:23 schrieb "Michael Van Canneyt" :
>
>
>
> On Mon, 21 Aug 2017, Ryan Joseph wrote:
>
>> I’m trying to split a string by a delimiter and see there is a type
helper called TStringHelper (
https://www.freepascal.org/docs-html/rtl/sysutils/tstringhelper.html). The
compiler version I’m using is "Free Pascal Compiler version 3.1.1
[2017/04/22] for i386” but when I include SysUtils the methods are not
found.
>>
>> For example:
>>
>> var
>>  str: string;
>>  parts: TStringArray;
>>
>> parts := str.Split(' ‘);
>>
>>
>> What am I doing wrong?
>
>
> Try
>
> var
>   Str : AnsiString;
> or
>   Str : WideString;
>
> I believe the compiler has some trouble finding the helper if you use the
> 'string' alias. I think there is even a bugreport about it.
> Sven Barth can confirm/deny this.

I thought that was fixed? Except of course if $H- is used (which is the
default in all modes except the Delphi ones) cause then String = AnsiString.

Regards,
Sven
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