[e-lang] Atomic expansion of MatchBindExpr to trinary-define

[Kevin Reid]

On May 1, 2006, at 1:46, Mark S. Miller wrote:

> Dean points out that if we give the trinary-define a syntax with a   
> left-to-right order that matches its execution order, (e1, e2, p),  
> then we can allow it to follow E's normal left-to-right scoping  
> rules without restriction. At that point, we should be able to  
> express MatchBindExpr as an expansion to trinary-define.

Is it truly necessary to provide left-to-right-define to support  
this? Isn't (using the "into" syntax I just posted)

   (def a := 1) into ^(fail) ==a

equivalent to

   def specimen__1 := (def a := 1)
   def ejector__2 := fail
   def ==a := (specimen__1, ejector__2)

Not that we should actually perform this expansion, but that it is  
possible to do the things we want without it.


That said, if we agree on a good syntax for left-to-right-define, I  
would prefer to have it as the Kernel-E construct, and remove the  
right-to-left trinary define syntax (e`def $a := ($b, $c)`) entirely.  
I only want the reasons for its inclusion to be sound.

-- 
Kevin Reid                            <http://homepage.mac.com/kpreid/>