Re: Generics - Difference between ADA and Modula--3

[dvdeug@x8b4e53cd.dhcp.okstate.edu (David Starner)]

On Mon, 5 Feb 2001 15:12:20 -0800, Mark Lundquist <mark@rational.com> wrote:
>> Ada designers made perfectly type-safe generics. Modula-3 designers looked
>> at Ada generics and C++ templates and decided the Ada generics were too
>much
>> of a PITA and went with a C++-style design that catches mistakes at
>link-time
>> rather than compile-time.
>
>Oh yeah... link-time errors, no pain there... :-)

Quote from language reference introduction (which explains the why and how
of many Modula-3 features):

| In the same spirit of simplicity, there is no separate typechecking 
| associated with generics. Implementations are expected to expand the 
| generic and typecheck the result. The alternative would be to invent 
| a polymorphic type system flexible enough to express the constraints 
| on the parameter interfaces that are necessary in order for the generic 
| body to compile. This has been achieved for ML and CLU, but it has not 
| yet been achieved satisfactorily in the Algol family of languages, 
| where the type systems are less uniform. (The rules associated with 
| Ada generics are too complicated for our taste.) 

(Note that this document was written prior to Ada 95.) 
The Introduction (http://www.research.compaq.com/SRC/m3defn/html/intro.html)
is an interesting look at the design of a "Algol family" (i.e. Ada, Oberon, 
the Modula's, Java) and some of the choices that could be made.

-- 
David Starner - dstarner98@aasaa.ofe.org
Pointless website: http://dvdeug.dhis.org
"I don't care if Bill personally has my name and reads my email and 
laughs at me. In fact, I'd be rather honored." - Joseph_Greg