In Mathematica, the expression:
Sort[{4, 3, 2, 1, -∞, ∞}]returns:
{1, 2, 3, 4, -∞, ∞}The behaviour is explainable, if unintuitive. Infinities
are different types of mathematical objects than, say, integers. Sort is
defined to sort objects into "canonical order". Apparently that order places infinities
after integers. Despite this explanation, the behaviour is definitely a gotcha to
watch out for.
The workaround is to specify Less as the ordering function for Sort
(instead of the default, OrderedQ):
Sort[{4, 3, 2, 1, -∞, ∞}, Less]