2009/10/17 Will Ness
Brent Yorgey
writes: By the way, the reason
map (+1) [1,2,3,4]
works but
map (-1) [1,2,3,4]
doesn't is because of an ugly corner of Haskell syntax: -1 here is parsed as negative one, rather than an operator section with subtraction. The 'subtract' function is provided exactly for this purpose, so that you can write
map (subtract 1) [1,2,3,4]
Then why wouldn't (`-`1) parse at at all? And not even (`(-)`1) ?
I know this doesn't parse, my question is, why wouldn't it be made valid syntax? It seems consistent. (`mod`2) parses, why not (`-`2) ?
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`This` syntax is used to make functions work infix, whereas operators already are infix. For this reason, it wouldn't make much sense to use `this` syntax (what's that called anyways?) on an operator. `(-)` would in some sense be the same thing as just "-", since () is used to make operators prefix and `` is used to make functions infix. -- Deniz Dogan