24 Jun
2011
24 Jun
'11
7:44 a.m.
On 24/06/2011 12:10, Daniel Fischer wrote:
On Friday 24 June 2011, 10:26:42, Guy wrote:
What does the ~ type operator mean? I've sometimes seen types such as (a ~ b) in error messages, but can't understand what GHC is trying to tell me.
Type equality, (a ~ b) means that a and b are the same type (rather, that the compiler can prove they're the same).
So where is it useful to say a ~ b, rather than using a twice?