gistfile1.txt

flip :: (a -> b -> c) -> b -> a -> c
id :: a -> a

      
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Given:
t = flip id

Step 1: Instantiate with unification variables:

(1) flip id :: _w
(2) flip :: (_s -> _t -> _u) -> _t -> _s -> _u
(3) id :: _v -> _v

Using (2) and (1) we get
(4) _w ~ (_t -> _s -> _u)
Substitute (4) into (1)
(5) flip id :: _t -> _s -> _u

From application we also get:
(6) (_v -> _v) ~ (_s -> _t -> u)
Which gives us:
(7) _v ~ _s
(8) _v ~ (_t -> _u)
Which gives us:
(9) _s ~ (_t -> _u)
Substitute (9) into (5)
10) flip id :: _t -> (_t -> _u) -> _u

We cant make any more progress, generalize over all left overs:

flip id :: a -> (a -> b) -> b