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From: CDCKAB%EMUVM1.BITNET@cunyvm.cuny.edu ( Karl Brendel)
Newsgroups: comp.lang.pascal
Subject: Re: Pointers to procedures
Message-ID: <26505@adm.brl.mil>
Date: 9 Apr 91 14:35:41 GMT
Sender: news@adm.brl.mil
Lines: 66

In article <9104081439.aa02828@VGR.BRL.MIL>, 209507097@ucis.vill.edu
  (MCREE, JAMES F) wrote:

>        I been following the thread of calling procedures by
>pointers with a lot of interest recently.  Mostly because I have an
>application that is just begging for a solution like that.  However,
>the discussion and samples that I have seen (including those in the
>manual) deal with hardcoding procedure names into the program.  (ie.
>Proc[i] := Do_It_Procedure)  Is there a way of doing what my
>syntactically incorrect program below is trying to do?
>
>Program Call_A_Variable_Procedure (Input,Output);
>.
>Var
>    Proc_Name : Procedure;
>.
>.
>Assorted necessary delcarations
>.
>Begin
>.
>.
>Assorted code statements
>.
>.
>Write ('Enter the name of a procedure to run: ');
>Readln (Proc_Name);
>Proc_Name;
>.
>.
>End.
>
>
>This is an example of a user-specified call to a procedure.  The
>user specifies the procedure directly though.  Can this be done?

It isn't really apparent (to me) that your application is truly
"begging for a solution like [pointers to procedures]". Why can you
not just use a series of IF statements for your purpose?

        Proc_Name := stUpCase(Proc_Name);
        IF Proc_Name = 'PROC_A' THEN Proc_A
        ELSE IF Proc_Name = 'PROC_B' THEN ProcB
        etc....

Note that you may want to let the user specify arguments prior to
calling the routine:

        Enter the name of a procedure to run (with arguments):

        proc_a(first_var, second_var)_

where the number of arguments may be different from routine to
routine. I don't think there's any way of doing that with proceure
types (or pointers thereto) which is really any more elegant or
compact than the series of IF statements. (But that's probably
shortsightedness on my part :) )

Cheers--                        --Karl

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