:: [a] package:fused-effects

Look up the previous accumulation

runAccum w look = return (w, w)
runAccum w (look >>= continuation) = runAccum w (continuation w)

Fail the current branch, and prevent backtracking within the nearest enclosing call (if any). Contrast with empty, which fails the current branch but allows backtracking.

cutfail >>= k = cutfail

cutfail <|> m = cutfail

Abort the computation. empty annihilates >>=:

empty >>= k = empty

Retrieve the environment value.

runReader a (ask >>= k) = runReader a (k a)

Get the current state value.

runState a (get >>= k) = runState a (k a)