[Haskell-cafe] Pattern matching does not work like this?

[Richard O'Keefe]

On Jul 15, 2009, at 9:59 PM, minh thu wrote:

> 2009/7/15 Magicloud Magiclouds <magicloud.magiclouds at gmail.com>:
>> Hi,
>> I do not notice this before. "fun ([0, 1] ++ xs) = .." in my code
>> could not be compiled, parse error.
>
> ++ is a function; you can't pattern-match on that.

Doesn't matter, it's not trying to.
Part of Erlang syntax is that in a pattern
	[c1,...,cn] ++ P
is equivalent to
	[c1,...,cn|P]

For example,
	wee(X) ->
	    F = fun ([0,1] ++ L) -> L end,
	    F(X).
is perfectly legal.

The problem might be the "xs", or it might be the "=".
Presumably it should be

	fun ([0,1] ++ Xs) -> ...