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From: Gautier <Gautier.deMontmollin@Maths.UniNe.CH>
Subject: Re: should I be interested in ada?
Date: 1999/02/15
Message-ID: <36C863E0.F79EFE5D@Maths.UniNe.CH>#1/1
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References: <7a72e6$g55$1@probity.mcc.ac.uk>
To: p.helbig@jb.man.ac.uk
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Newsgroups: comp.lang.ada
Date: 1999-02-15T00:00:00+00:00
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> I'm actually quite happy programming in Fortran95 but Ada seems to be
> the one language I regularly hear good things about (which also seem
> believable AND relevant to me).
> 
> Is there any reason to use Ada as opposed to Fortran95 for my stuff
> (mainly number crunching, numerical analysis etc, some home-grown
> graphics software, relatively simple text processing etc; almost all
> code I use is my own)?

The pluses: see below
The minus: as for every language change there are decisions to take
with the software already done:
- translate (f2a perl script does the most)
- interface when it would take too long to translate - see example as P.S.

In terms of time, in my own project, the minus has costed me a week,
the pluses have saved me about 6 months. So far I didn't need a
debugger! It lets me plenty of time to read and answer the news 8-� !

> What are the main advantages/disadvantages of Fortran and Ada?

Ada has been conceived with the experience of mistakes done with old
languages (Fortran, C,...) and by clever people.

You'll enjoy, among others:

- readibility
- well-done variable visibility: important for large numerics programs
- strong typing which allows to catch plenty of mistakes
- bounds of arrays always obtainable (that can be save plenty of hairs
  nerves, keyboards in usual Fortran programming life)
- exceptions: replaces complicated Fortran error management codes
  useful when a 0 determinant should result as an error in a context
  and not in another (see P.S., "raise" statements)
- modularity
- portability

The combination of the 2 latter allows me to use the same source file
containing a Finite Element library for my calculations under OpenVMS (DEC Ada)
and for the graphics program on PC (GNAT/DOS) to interpolate positions in
elements, for displaying results.

> How many platforms have ada compilers (in principle AND in practice)?

Just for the freeware GNAT, there are plenty!
Here is a list of the "official" ones: http://www.gnat.com/platforms.HTM

-- 
Gautier

--------
Homepage: http://www.unine.ch/math/Personnel/Assistants/Gautier/Montmollin.html
Software: http://www.unine.ch/math/Personnel/Assistants/Gautier/Gaut_FTP.htm.

PS: example of interfacing Fortran/Ada for LAPACK (perhaps could be made simpler,
    but it works...)

--------------
--- DPBTRF ---
--------------

  procedure DGBTRF_f(M,N, KL,KU: Natural;
                     AB: in out Matrix; LDAB: Positive; IPIV: out IVector;
                     INFO: out Integer);

  PRAGMA Interface (FORTRAN, DGBTRF_f);
  PRAGMA Import_Procedure(Dgbtrf_f, Dgbtrf,
  Parameter_Types => (Natural,Natural,Natural,Natural,
                      Matrix,Positive,IVector,Integer),
  Mechanism => (Reference,Reference,Reference,Reference,
                Reference,Reference,Reference,Reference));

  procedure DGBTRF(M,N, KL,KU: Natural;
                   AB: in out Matrix; LDAB: Positive; IPIV: out IVector) is
    begin
      DGBTRF_f(M,N,KL,KU,AB,LDAB,IPIV,INFO);
      if INFO<0 then raise Illegal_value;
      elsif INFO>0 then raise Computation_error;
      end if;
    end;