W : ('a -> 'a -> 'b) -> 'a -> 'b

SYNOPSIS
Duplicates function argument : W f x equals f x x.

DESCRIBE

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.

FAILURE

W f never fails. W f x fails if f x fails or if f x x fails.

EXAMPLE
    - 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

SEEALSO  Lib,   \#\#,   A,   B,   C,   I,   K,   S

HOL  Kananaskis 0