Re: Generics???

[James Rogers <jimmaureenrogers@worldnet.att.net>]

Short answer: You can't. It would be a violation of Ada's strong
typing.

Integer types and float types are not implicitly convertable from one
to the other. The problem is specifically the arithmetic operators for
each type, as well as some of the attributes of each type.

If you only want to compare values for equality, or assign one value
to another, then you can specify the generic formal parameter to be
private. If you want to perform arithmetic you must be specific about
whether the type is a floating point type, a fixed point type, an
integer type, or a modular type. Each type has its own definition of
the arithmetic operators. The LRM does not require compilers to
support ambiguity in the arithmetic operators for numeric types.

In a language such as C++ the compiler would simply
promote all integer types to doubles, perform the calculations, 
then (possibly) convert back to the template parameter's actual
type. This is possible because C++ allows implicit conversion of
all integer types to any floating point type. C++ also does not
have an equivalent to Ada attributes. Many attributes of floating
point types are not shared by integer types. 

Jim Rogers
Colorado Springs, Colorado USA

Michael Andersson wrote:
> 
> Hi!
> How do I specify that the generic parameter is a integer or a float. I
> know that you can use
> type T is range <> to specify that T is any Integer-type and that you
> can use type T is digit <> to specify that T is any type of float. But
> how can I use both at the same time?
> I've tried to use type T is private but then I can't use any of the
> +,-,*,/ operators.
> 
> Need your help, please!
> /Michael Andersson