Functions that act as identity function for their own return values.
@emareaf Better way to say that: let X be any subset, and define f:
f(x) = -x if x and -x are both in X
f(x) = x otherwise
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@St_Rev I am unclear on how the kind of functions you're talking about relate to the kind of functions I'm talking about. -
@emareaf If f(f(x)) = f(x), then f(x) must be the identity function on its *range*. -
@emareaf I think that's a necessary and sufficient criterion. -
@emareaf Anyway this kind of function is sometimes called a 'retract'.
End of conversation
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. Banned in Sweden. SubGenius, Zhuangist, white-hat troll. Defrocked mathematician. Brain problems.