[e-lang] Is the SuchThatPattern always a bad idea?

Darius Bacon darius at accesscom.com
Mon Aug 8 08:57:15 EDT 2005


Mark Miller <markm at cs.jhu.edu> wrote:
> Unfortunately, the proposed new expansions combined with the no-cycle rule 
> will cause some E patterns, which seem to make perfect sense by the 
> left-to-right rule, to be rejected because their expansion to Kernel-E 
> violates the no-cycle rule:

Have you considered adding an equivalent form with the guard before
the pattern?  I hate to suggest complicating the language like that,
but given the above wart, the language could actually be simpler in a
way with the extra syntax.

(And of course if the guard *always* preceded the pattern, that'd fit
better into the C/Java syntactic tradition.  I'll be sure to bring it
up if I ever travel back in time to when E was getting invented...)

Darius


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