Re: access function in strings.maps

[Stephen Leake <Stephen.Leake@gsfc.nasa.gov>]

Dennis W. Butler wrote:
> 
> I've been exploring the string handling capabilities of Ada95 and have
> stumbled across a Thing I can't figure out. In the strings.maps package
> (LRM section A.4.2), there is a type definition that reads:
> 
> type Character_Mapping_Function is access function (From : in character)
> return character;
> 
> I would have thought a Character_Mapping_Function would be more like:
> 
> function Character_Mapping_Function (The_Map: in Character_Mapping;
> Domain_Character: in Character) return Character; -- range character
> 
Nope, 'Character_Mapping_Function' is used for _encoding_ a complex map
as a function.

> Although I read LRM section 3.10, I couldn't figure out the access
> function type definition. Where can I get an explanation of what the
> type definition does and how I can use it? I did note that the LRM says
> that the Character_mapping_Function is used for transformational
> mappings in the Translate subprograms...does this mean I'm not supposed
> to worry about it?

Thus Translate takes a 'Character_Mapping_Function' as a parameter to
specify the map. I got this explanation from Cohen's "Ada as a Second
Language"; a very good and thorough book. For a list of other good
books, see:

http://www.adahome.com/Resources/Books/ada95reviews.html
 
> Thanks,
> 
> Dennis Butler
> Computer Science Department
> Cal Poly, San Luis Obispo

You're welcome.
-- 
- Stephe