passing an array to a generic function

passing an array to a generic function

[Mr. J.]

hi,

this is my generic function:

generic
   type Index is (<>);
   type Item is private;
   type Arr is array(Index range <>) of Item;
   with function "="(I1,I2 : Item) return Boolean is <>;
   
   function Filter_Array(A: Arr) return Arr;

Now, I wanna write a create a Filter_String function according to it:

   type Index is new Integer;
   type Item is new Character;
   type Arr is Array(1..23) of character;
   
   function Filter_String is new Filter_Array(Index,Item,Arr,"=");

As U all experts guessed it won't compile, my question is how to pass
the array of character to my new function ?

10x,
J.

Re: passing an array to a generic function

[Lutz Donnerhacke]

* Mr. J. wrote:
>    type Index is new Integer;
>    type Item is new Character;
>    type Arr is Array(1..23) of character;

type Arr is Array(1 .. 23) of Item;

Item is different from Character.

Re: passing an array to a generic function

[David C. Hoos]

You need to understand and act on the messages the
compiler sends you.

Accordingly, the following code will compile:

generic
   type Index is (<>);
   type Item is private;
   type Arr is array(Index) of Item;
   with function "="(I1,I2 : Item) return Boolean is <>;

   function Filter_Array(A: Arr) return Arr;

   type Index is new Integer range 1 .. 23;
   type Item is new Character;
   type Arr is Array(Index) of Item;

   function Filter_String is new Filter_Array(Index,Item,Arr,"=");

However. when you declare types as new "some other type",
you're creating new types that are distinct from
the "some other type."  Therefore, if as the name of
your instantiation implies, you intend to pass objects
of type string to it, you would do better to do this:

generic
   type Index is (<>);
   type Item is private;
   type Arr is array(Index) of Item;
   with function "="(I1,I2 : Item) return Boolean is <>;

   function Filter_Array(A: Arr) return Arr;

   subtype Index is Integer range 1 .. 23;
   subtype Arr is String (Index);

   function Filter_String is new Filter_Array(Index, Character, Arr, "=");

"Mr. J." <ratsonjaniv@hotmail.com> wrote in message
news:fc116fae.0311210231.d4a9515@posting.google.com...
> hi,
>
> this is my generic function:
>
> generic
>    type Index is (<>);
>    type Item is private;
>    type Arr is array(Index range <>) of Item;
>    with function "="(I1,I2 : Item) return Boolean is <>;
>
>    function Filter_Array(A: Arr) return Arr;
>
> Now, I wanna write a create a Filter_String function according to it:
>
>    type Index is new Integer;
>    type Item is new Character;
>    type Arr is Array(1..23) of character;
>
>    function Filter_String is new Filter_Array(Index,Item,Arr,"=");
>
> As U all experts guessed it won't compile, my question is how to pass
> the array of character to my new function ?
>
> 10x,
> J.
> _______________________________________________
> comp.lang.ada mailing list
> comp.lang.ada@ada-france.org
> http://www.ada-france.org/mailman/listinfo/comp.lang.ada
>
>

Re: passing an array to a generic function

[Jean-Pierre Rosen]

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"Mr. J." <ratsonjaniv@hotmail.com> a �crit dans le message news:
fc116fae.0311210231.d4a9515@posting.google.com...
>    type Index is new Integer;
>    type Item is new Character;
>    type Arr is Array(1..23) of character;
>
>    function Filter_String is new Filter_Array(Index,Item,Arr,"=");
>
> As U all experts guessed it won't compile, my question is how to pass
> the array of character to my new function ?
>
In Ada, all types must match *exactly*. Therefore, you must define Arr as:
type Arr is array (Index range 1..23) of Item;

(1..23 has type Integer, not Index. And Item is a type different from
Character).

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