7 Apr
2009
7 Apr
'09
1:16 a.m.
On Mon, Apr 6, 2009 at 10:09 PM, Eugene Kirpichov
Since the argument to sortBy must impose a linear ordering on its arguments, and any linear ordering may as well be generated by assigning an integer to each element of type 'a', and your sorting function is polymorphic, from the free theorem for the sorting function we may deduce that it suffices to test your function on integer lists with a casual comparison function (Data.Ord.compare), and there is no need to generate a random comparison function.
Interesting. How is this free theorem stated for the sorting function? Intuitively I understand that if the type is polymorphic, then it seems reasonable to just pick one type and go with it. Thanks, Jason