Function: setisset
Section: linear_algebra
C-Name: setisset
Prototype: lG
Help: setisset(x): true(1) if x is a set (row vector with strictly
 increasing entries), false(0) if not.
Doc:
 returns true (1) if $x$ is a set, false (0) if
 not. In PARI, a set is a row vector whose entries are strictly
 increasing with respect to a (somewhat arbitrary) universal comparison
 function. To convert any object into a set (this is most useful for
 vectors, of course), use the function \kbd{Set}.
 \bprog
 ? a = [3, 1, 1, 2];
 ? setisset(a)
 %2 = 0
 ? Set(a)
 %3 = [1, 2, 3]
 @eprog
