[Fwd: Re: Adding if/then/else statement to GMPL]

[Andrew Makhorin]

-------- Forwarded Message --------
From: Jeffrey Kantor <jeff.kantor@gmail.com>
To: "Meketon, Marc" <Marc.Meketon@oliverwyman.com>
Cc: Andrew Makhorin <mao@gnu.org>, Domingo Alvarez Duarte <mingodad@gmai
l.com>, help-glpk@gnu.org <help-glpk@gnu.org>
Subject: Re: Adding if/then/else statement to GMPL
Date: Mon, 24 Aug 2020 09:54:33 -0500

> This would be another vote for extending GMPL to include features to
> support the iterative use of LP’s. As is stands, GMPL is a sweet
> little modeling tool … a well-crafted application is small work of art
> that is generally clear and unambiguous. One mark fo a good model is
> the ability to go back years later and instantly recall the logic
> behind the model. 
> 
> There are so many more applications where iteration is a natural part
> of the modeling. Stocking cutting, for example. Stochastic
> programming. With these features, GMPL could continue to be a useful
> tool for developing and documenting models and MILP applications.
> Without these features, tools like PULP and Pyomo become the lingua
> franca of the field.
> 
> > On Aug 24, 2020, at 9:00 AM, Meketon, Marc via Users list for GLPK
> > (GNU Linear Programming Kit) <help-glpk@gnu.org> wrote:
> > 
> > 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/9d70a37b16bd377722eeb3880f
> > > cf86
> > > 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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>