# [racket] arity of + versus <=

Think about arithmetic mod 2. Multiplication is AND and addition is XOR. So the multiplicative identity 1 corresponds to TRUE. It just happens that the additive identity 0 works for OR, but that's not a perfect analog since 1 + 1 = 0 (2).
On Oct 28, 2011, at 9:55 AM, Carl Eastlund wrote:
>* No. I don't see any sense in which that's a generalization of cdr.
*>* In fact it's quite non-uniform; for instance, applying cdr to a
*>* non-empty list produces a list one shorter. If we want to extend cdr
*>* to length 0 lists, we need to somehow produce a list of length -1. We
*>* restrict cdr from empty lists precisely because it can't be
*>* generalized. Or at least that's how I see it.
*>*
*>* --Carl
*
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