Your intuition that id is related to const is a good one, since id can be defined in terms of const. Here is one of many: id' = flip const const [This is also called a CKK combinator. See http://en.wikipedia.org/wiki/S_combinator#Combinatory_calculi for more examples, such as SKK, SKS, and various other identity equivalents.] Whether these are "different" identity functions is an interesting question. Ask yourself how you could tell them apart. What if they both always gave the same answer, but one always took longer than the other? Are you allowed to "peek at the code" before deciding on equality? Does it even matter whether there is only one identity? [AKA, is function application faithful?] Interesting stuff. More at: http://en.wikipedia.org/wiki/Semiautomaton Dan PR Stanley wrote:
Hi is const = id? const 'x' 'y' 'x' id 'x' 'x'
Cheers, Paul
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