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12.5.3 Formal Array Types

The class determined for a formal array type is the class of all array types.

Syntax

   
       formal_array_type_definition ::= array_type_definition

Legality Rules

The only form of discrete_subtype_definition that is allowed within the declaration of a generic formal (constrained) array subtype is a subtype_mark.

For a formal array subtype, the actual subtype shall satisfy the following conditions:

• The formal array type and the actual array type shall have the same dimensionality; the formal subtype and the actual subtype shall be either both constrained or both unconstrained.

• For each index position, the index types shall be the same, and the index subtypes (if unconstrained), or the index ranges (if constrained), shall statically match (see 4.9.1).

• The component subtypes of the formal and actual array types shall statically match.

• If the formal type has aliased components, then so shall the actual.

Examples

Example of formal array types:

    
       --  given the generic package

       generic
          type Item   is private;
          type Index  is (<>);
          type Vector is array (Index range <>) of Item;
          type Table  is array (Index) of Item;
       package P is
          ...
       end P;

       --  and the types

       type Mix    is array (Color range <>) of Boolean;
       type Option is array (Color) of Boolean;

       --  then Mix can match Vector and Option can match Table

       package R is new P(Item   => Boolean, Index => Color,
                          Vector => Mix,     Table => Option);

       --  Note that Mix cannot match Table and Option cannot match Vector

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