NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/comp/lang/pascal/6643

Text File | 1992-11-17 | 3.0 KB | 91 lines

Newsgroups: comp.lang.pascal
Path: sparky!uunet!utcsri!newsflash.concordia.ca!IRO.UMontreal.CA!iros1!shen
From: [e-mail] (Yu Shen)
Subject: Re: Turbo and Procs/Fns as params..
In-Reply-To: [e-mail]'s message of Mon, 16 Nov 1992 13: 05:29 GM
Message-ID: <[e-mail]>
Sender: [e-mail]
Organization: Universite de Montreal -- Laboratoire Incognito
References: <[e-mail]> <[e-mail]>
    <[e-mail]> <[e-mail]>
    <[e-mail]>
    <[e-mail]>
Date: Tue, 17 Nov 1992 02:21:35 GMT
Lines: 75

In article <[e-mail]> [e-mail] (Duncan Murdoch) writes:

> Newsgroups: comp.lang.pascal
> Path: IRO.UMontreal.CA!newsflash.concordia.ca!uunet!cis.ohio-state.edu!zaphod.mps.ohio-state.edu!cs.utexas.edu!torn!news.ccs.queensu.ca!slip203.telnet1.QueensU.CA!dmurdoch
> From: [e-mail] (Duncan Murdoch)
> Lines: 33
> Sender: [e-mail] (Netnews control)
> Organization: Queen's University
> References: <[e-mail]> <[e-mail]> <[e-mail]> <[e-mail]> <[e-mail]>
> Date: Mon, 16 Nov 1992 13:05:29 GMT

> In article <[e-mail]> [e-mail] (Rich Holland) writes:
>>Turbo Pascal *DOES* Allow you to pass Procedures and Functions as parameters.
>>Unless I misinterpreted your comment....
>
>...but only if you pass them as a *pointer*

> It's true that you don't pass the actual code around, but you don't need to
> explicitly use pointers.  For example:

{$F+}  { this is necessary, since procedures to be assigned must be far }
>
>   function add(a,b:integer):integer;
>   begin add := a+b end;

>   function subtract(a,b:integer):integer;
>   begin subtract := a-b end;

>   type
>     binaryop = function(a,b:integer):integer;

>   var
>     someop : binaryop;

>   begin
>     someop := add;
>     writeln('Some op of 5 and 3 is ',someop(5,3));
>   end.

> The implementation makes someop a pointer to the entry point of the add
> function here, but the syntax hides that.

> Duncan Murdoch
> [e-mail]

I just have a related problem that it seemed to me that member
function can not be as value for such procedure variable.

Here is the example modified from the above:

AnObject = object
   function add(a,b:integer):integer; {wrap it into an object}
end;

function AnObject.add(a,b:integer):integer;
   begin add := a+b end;

   type
     binaryop = function(a,b:integer):integer;

   var
     someop : binaryop;
     theObject: AnObject;
   begin
     someop := theObject.add; {it may not work, here, though, I didn't
try $F+}
     writeln('Some op of 5 and 3 is ',someop(5,3));
   end.
--
Yu Shen
Dept. d'Informatique et Recherche Operationnelle
University de Montreal, C.P. 6128 Succ. A.
Montreal, Que. Canada, H3C 3J7

[phone] (H) [e-mail]