- (pairwise-not=? compare x[1] ...)procedure
Tests if the values x[1] ...(zero or more values) are pairwise unequal with respect to the compare procedure compare. The result is a boolean (either #t or #f). The order in which the values are compared is unspecified, but each value is compared at least once (even if there is just one).
The values x[1], ..., x[n] are pairwise unequal if (not=? compare x[i] x[j]) for all i j. In particular, this is the case for n {0,1}.
Since compare defines a total ordering on the values, the property can be checked in time O(n log n), and implementations are required to do this. (For example by first sorting and then comparing adjacent elements).