[e-lang] Call patterns

[Mark S. Miller]

This is in reply to old e-lang message
http://www.eros-os.org/pipermail/e-lang/2006-May/011268.html

Kevin Reid wrote:
> This is something I'm playing with in E-on-CL.
> 
>    def a.b(c) := d
> 
> expands to
> 
>    via (__makeVerbFacet.curryCall(a, "match__b/1")) [c]
> 
> The idea is that call patterns are a form of extensible pattern which  
> is more suitable than quasi-patterns for objects which do not  
> naturally have a (semi-) textual syntax.
> 
> The receiver in a call pattern is an expression, the verb is  
> constant, and the arguments are patterns, so it asks the receiver to  
> match the specimen and return a list of components to be matched  
> against the subpatterns.
> 
> For example:
> 
>      def Ref {
>        ...
>        to "match__broken/1"(r, ej) :any {
>          if (Ref.isBroken(r)) {
>            return [Ref.optProblem(r)]
>          } else {
>            throw.eject(ej, makeNotBrokenMismatch(r))
>          }
>        }
>      }
> 
>    # without call-pattern
>    if (Ref.optProblem(ref) =~ p :notNull) { ... }
> 
>    # with call-pattern
>    if (ref =~ Ref.broken(p)) { ... }


This seems very plausible - I like it. Let's decide on a pragma.enable/1 
switch name for enabling it, so we can experiment with it before deciding to 
add it officially to E. How about

     pragma.enable("call-pattern")

?
What's its BNF?

The need to add this to E-on-Java is now bug
https://sourceforge.net/tracker/index.php?func=detail&aid=1527171&group_id=75274&atid=551529

-- 
Text by me above is hereby placed in the public domain

     Cheers,
     --MarkM