a beginner question

a beginner question

[mr1yh1]

i am very new in ada , i try to write codes from book and see  result
i tried something but i couldnt get a good result
(i use gnat)

******************
with Ada.Text_Io;use Ada.Text_Io;
procedure test is 
   type Sex_T is 
         (Male,  
          Female); 

   type Person ( S:Sex_T:=Male )is
   record
      Age:Positive ;
      Sex:Sex_T:=S;------please look at here first
      case S is
         when Male =>
            Has_Wife:Boolean ;
         when Female=>
            Has_Husband:Boolean;
      end case;
   end record;--person end
   Me   : Person;  
   she : Person (Female);  ---- and this one , 
begin
   Me:=(
      S        => Male,                         
      Sex      => Male,                         
      Age      => 33,                           
      Has_Wife => True);
   she:=(
      S           => Female,                       
      Sex         => Male, ---please look at here now!!!!!                
       
      Age         => 23,                           
      Has_Husband => True);
   Put(Sex_T'Image(she.Sex));
end test;

****
there is not any alert
and result is 
" male " ??

if i dont put "sex=>male" , or "sex=>female"
it dont let me to use a named association...

even is i dont put  " s=> female " 
it dont let me too , 
but i said about discriminant 
when i declare the variable ( she : person(female) )

why  its not possible ?
to put
she:=(age=>23,has_husband=>true);
 

regards

Re: a beginner question

[Björn Persson]

mr1yh1 wrote:

>    type Person ( S:Sex_T:=Male )is
>    record
>       Age:Positive ;
>       Sex:Sex_T:=S;------please look at here first
>       case S is
>          when Male =>
>             Has_Wife:Boolean ;
>          when Female=>
>             Has_Husband:Boolean;
>       end case;
>    end record;--person end

You have defined a person with two independent sexes. By default, Sex is 
initialized to the same value as S, but it's perfectly possible to 
change it.

Just remove Sex and let S be the person's sex.

>    Put(Sex_T'Image(she.Sex));

This line then becomes:

    Put(Sex_T'Image(she.S));

> why  its not possible ?
> to put
> she:=(age=>23,has_husband=>true);

The parenthesis here is called an aggregate. An aggregate must provide 
values for all the components. But you can do:

    She.Age := 23;
    She.Has_Husband := True;

-- 
Björn Persson                              PGP key A88682FD
                    omb jor ers @sv ge.
                    r o.b n.p son eri nu

Re: a beginner question

[Marius Amado Alves]

Discriminated types don't let you do indiscriminated things on them :-)

Proficiency with discriminated types is a big part of being an Ada 
expert. Read the chapter on discriminated types of an Ada textbook. 
Ben-Ari's or Barnes'es.

In the meanwhile and for the things you seem to be trying to do you can 
safely use a normal type and constructor functions.

mr1yh1 wrote:
> i am very new in ada , i try to write codes from book and see  result
> i tried something but i couldnt get a good result
> (i use gnat)
> 
> ******************
> with Ada.Text_Io;use Ada.Text_Io;
> procedure test is 
>    type Sex_T is 
>          (Male,  
>           Female); 
> 
>    type Person ( S:Sex_T:=Male )is
>    record
>       Age:Positive ;
>       Sex:Sex_T:=S;------please look at here first
>       case S is
>          when Male =>
>             Has_Wife:Boolean ;
>          when Female=>
>             Has_Husband:Boolean;
>       end case;
>    end record;--person end
>    Me   : Person;  
>    she : Person (Female);  ---- and this one , 
> begin
>    Me:=(
>       S        => Male,                         
>       Sex      => Male,                         
>       Age      => 33,                           
>       Has_Wife => True);
>    she:=(
>       S           => Female,                       
>       Sex         => Male, ---please look at here now!!!!!                
>        
>       Age         => 23,                           
>       Has_Husband => True);
>    Put(Sex_T'Image(she.Sex));
> end test;
> 
> ****
> there is not any alert
> and result is 
> " male " ??
> 
> if i dont put "sex=>male" , or "sex=>female"
> it dont let me to use a named association...
> 
> even is i dont put  " s=> female " 
> it dont let me too , 
> but i said about discriminant 
> when i declare the variable ( she : person(female) )
> 
> why  its not possible ?
> to put
> she:=(age=>23,has_husband=>true);
>  
> 
> regards
> 
> _______________________________________________
> comp.lang.ada mailing list
> comp.lang.ada@ada-france.org
> http://www.ada-france.org/mailman/listinfo/comp.lang.ada
> 

Re: a beginner question

[mr1yh1]

thank you for all comments
i read more about discriminants 
and i realised 
they are different things that i used to use till now :)...

i realise my mistake too , 
i made it possible to access a variable in two ways
( first discriminant give a value ,but its a record and its possible to
change it, in normal ways )

and i see now 
the right way to use discriminants give a chance to do something which is
not possible  in another way ...
i saw in the examples:
-- they make possible to initialize the types of variables
( arrays,strings ...)
-- and they make possible to use different spesifications in same record
for different discriminant values

regards