RE: Adding if/then/else statement to GMPL

[Meketon, Marc]

I've always felt that GMPL needed if-then-else, for-loops, 'let' statements and 
the ability to re-solve to be a true modeling language.  And Andrew has always 
disagreed.

Many of the models that I create ultimately are 'iterative' where I need to 
take the results of one model and use it to setup another model.  To me, that 
is also modeling.  GMPL doesn't have it.

So often, I use GMPL for an initial model - it is a wonderful language, and I 
find it faster to code than alternatives.  But then when I 'get it right' I 
have to re-code it in PYOMO or PULP or write directly to an 'lp' file within a 
Python or C# or other language script.

Having the ability to run, adjust variables, add/take away constraints, re-run 
would be extremely useful, and make GMPL more of a one-stop modeling language.

-----Original Message-----
From: Help-glpk <help-glpk-bounces+marc.meketon=oliverwyman.com@gnu.org> On 
Behalf Of Andrew Makhorin
Sent: Sunday, August 23, 2020 2:56 PM
To: Domingo Alvarez Duarte <mingodad@gmail.com>; help-glpk@gnu.org
Subject: Re: Adding if/then/else statement to GMPL

On Sun, 2020-08-23 at 15:36 +0200, Domingo Alvarez Duarte wrote:
> Hello !
>
> Also I've added the break/continue statements here
> https://github.com/mingodad/GLPK/commit/9d70a37b16bd377722eeb3880fcf86
> bb3b812118
>
>
> Again any comment/suggestion is welcome !
>
> Cheers !
>
>
>

Please note that GNU MathProg is a *modeling* language; it is not a 
general-purpose programming language. If you need to produce a non-trivial 
solution report (since all such-like statements are allowed only on the 
post-solving stage), it would be more practical to write the solution to a 
temporary file and then process it with a separate program.




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