> What do the following definitions do:
>
>1 x + 1 = f x
>
>2 (x + 1) = f 2
>
>I don't propose to change this, because in practice it doesn't seem
>to cause much of a problem, but it seems pretty confusing. To my mind
>the culprit is clear: n+k patterns. But they are staying in Haskell 98.
I've simplified the problem by dropping two alternatives - I'll tweak 1
above little, to give 1` - lets write these together again
1` x + 1 = f 2
2 (x + 1) = f 2
Now,
>(1`) partially defines (+).
>(2) is a pattern binding that binds x.
Ho-hum - the only difference between these two pieces of concrete syntax
is that one wraps construct ("x + 1") in parentheses, the other doesn't.
Parentheses are usually used in mathemtaica and programming notations
as a syntactical guide to the parsing of expression - a form of hinting
regarding the desired underlying abstract syntax, or parse tree.
IMHO (which of course is never humble :-) the real problem here,
that causes most of the confusiuon, is that THESE parentheses (2 above)
have different semantics - leave them out and we partiall define (+),
put them in and we pattern bind x
I don't care about n+k patterns one way or another - I am a lazy functional
programmer and will happily write 'n' instead of 'n+1' wherever that will
do :-)
I think the real confusion here is the semantic role being played by symbols
that are traditionally used as syntactical structure indicators.
-------------------------------------------------------------
Andrew Butterfield, Location: LG.19
Dept. of Computer Science, Tel: +353-1-608-2517
O'Reilly Institute, Fax: +353-1-677-2204
Trinity College,
Dublin 2, IRELAND. mailto:[EMAIL PROTECTED]
URL: http://www.cs.tcd.ie/Andrew.Butterfield/
