W : ('a -> 'a -> 'b) -> 'a -> 'b
The W combinator can be understood as a planner: in the application f x x, the function f can scrutinize x and generate a function that then gets applied to x.
W f never fails. W f x fails if f x fails or if f x x fails.
- load "tautLib"; - tautLib.TAUT_PROVE (Term `(a = b) = (~a = ~b)`); > val it = |- (a = b) = (~a = ~b) : thm - W (GENL o free_vars o concl) it; > val it = |- !b a. (a = b) = (~a = ~b) : thm