Re: schema pointer compatibility

On 13 Aug 2012 at 10:46, Jay Michael wrote:

>      Why isn't the address of an object of a schema type an acceptable
> value for a pointer to the (undiscriminated) schema type?
> 
> type sptr_type = ^ string ;
> type sptr_array_type( n : integer ) = array [ 1 .. n ] of sptr_type ;
> type sptr_array_ptr_type = ^ sptr_array_type ;
> 
> const s1 = 's1' ;
> const s2 = 's2' ;
> const s3 = 's3' ;
> 
> const slist : sptr_array_type(3) = ( @s1, @s2, @s3 ) ;
> 
> var slist_ptr : sptr_array_ptr_type = @slist ;
> 
> 
> t12.pas:23: error: assignment from incompatible pointer type
> 
> 
>      I got the same error when I changed "slist" (the object of the
> discriminated schema type) from a "const" to a "var".
>      I got the same error when I tried using an assignment statement:
> 
>           var slp : sptr_array_ptr_type ;
>           ...
>           slp := @slist ;
> 
>      If a discriminated instance of a schema type isn't quite the
> same type as the undiscriminated type, then when would I ever be
> able to use the address of an object as a value for a pointer to
> the undiscriminated type?  (without coercion, that is)

Because what you are trying to do is rejected by the standards that you 
are implicitly following. Compile with "--no-typed-address", and it 
will compile.

Best regards, The Chief
--------
Prof. Abimbola A. Olowofoyeku (The African Chief) 
web:  http://www.greatchief.plus.com/


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