15 Jul
2013
15 Jul
'13
12:32 p.m.
On Mon, 15 Jul 2013, Sturdy, Ian wrote:
Consider also among unquestionably useful instances that violate simple prejudice the Num instance for `Num a => Set a`, where `a + {1,-1} - {1,-1} == {a-2,a,a+2}`.
That's the main reason why a Num instance of Sets is a bad idea. If you continue that way you will soon end up in MatLab mess. In MatLab every number is actually a complex valued matrix. So will the next proposal be an 'instance IsString (Set a)'? Or 'instance IsString [a]' (for every a/=Char)?