- (chain>=? compare x[1] ...)procedure
Test if the values x[1] ...(zero or more values) form a chain with respect to the relation specified by the name of the procedure, and 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.)
A sequence of values x[1], ..., x[n] forms a chain with respect to the relation rel? if (rel? compare x[i] x[j]) for all 1 < i < j < n. In particular, this is the case for n {0,1}.
Since the relations = , <, >, <, and > are transitive, it is sufficient to test (rel? compare x[i] x[i+1]) for 1 < i < n.
Note: The reason every x[i] participates in at least one comparison is type-checking: After testing if the values form a chain, these value may be assumed to be of the type comparable by compare -- and this holds irrespectively of the number of values, or whether they form a chain.