parameters evaluation

parameters evaluation

[Sami Evangelista]

hello all

i have noticed a strange thing about expressions evaluations during a 
procedure or function call. it appears that the parameters are evaluated 
in the "wrong" order. Try this

-------------------------------------------------------------
with ADA.TEXT_IO;
use ADA.TEXT_IO;

procedure Proc is
    function F return Boolean is begin Put_Line("F"); return True; end;
    function G return Boolean is begin Put_Line("G"); return True; end;
    function H(B1, B2 : in Boolean) return Boolean is
    begin
       put_Line("H");
       return True;
    end;

begin
    if H(F, G) then null; end if;
end;
-------------------------------------------------------------

the output should "logically" be
F
G
H

but it is
G
F
H

so be careful if your functions change global variables or have others 
effects which is by the way not very clean.

Sami Evangelista

Re: parameters evaluation

[Simon Wright]

Sami Evangelista <sami.evangelista@wanadoo.fr> writes:

> i have noticed a strange thing about expressions evaluations during a 
> procedure or function call. it appears that the parameters are evaluated 
> in the "wrong" order. Try this
[...]
> the output should "logically" be
> F
> G
> H
> 
> but it is
> G
> F
> H

I think you are wrong to say that your compiler is acting "wrong" or
not "logically".

See ARM 6.4(10) at http://www.adaic.org/standards/95lrm/html/RM-6-4.html -

   For the execution of a subprogram call, the name or prefix of the
   call is evaluated, and each parameter_association is evaluated (see
   6.4.1). If a default_expression is used, an implicit
   parameter_association is assumed for this rule. These evaluations
   are done in an arbitrary order.

Re: parameters evaluation

[Jean-Pierre Rosen]

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"Sami Evangelista" <sami.evangelista@wanadoo.fr> a �crit dans le message
news: 3D947171.2040909@wanadoo.fr...
> hello all
>
> i have noticed a strange thing about expressions evaluations during a
> procedure or function call. it appears that the parameters are evaluated
> in the "wrong" order. Try this
>
[snip]
The order of evaluation of parameters is not defined by the language. The
output of the program is correct.

--
---------------------------------------------------------
           J-P. Rosen (rosen@adalog.fr)
Visit Adalog's web site at http://www.adalog.fr