The Grinnell Scheme Web: The odd?
procedure

What exactly is the parity of a number?

The parity of an integer is whether it is even or odd -- that is, whether or not it is evenly divisible by 2. Only integers have parity.

How do you determine the parity of an integer in Scheme?

You have your choice of two procedures, odd? and even?. They're exactly complementary. If you're watching out for an integer that is not evenly divisible by 2 for some reason, call the odd? procedure:

> (odd? 7)
#t
> (odd? -8)
#f
> (odd? 0)
#f
> (odd? 5.9)

ERROR: odd?: Wrong type in arg1 5.9
The arity of the odd? procedure is 1, and the operand must be an integer.


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This document is available on the World Wide Web as

http://www.math.grin.edu/~stone/scheme-web/odd-ques.html


created July 2, 1995
last revised December 29, 1995

Copyright 1995 by John David Stone (stone@math.grin.edu)