state package:mtl

Embed a simple state action into the monad.
State monads. This module is inspired by the paper Functional Programming with Overloading and Higher-Order Polymorphism, Mark P Jones (http://web.cecs.pdx.edu/~mpj/) Advanced School of Functional Programming, 1995.
A state monad parameterized by the type s of the state to carry. The return function leaves the state unchanged, while >>= uses the final state of the first computation as the initial state of the second.
A state transformer monad parameterized by:
  • s - The state.
  • m - The inner monad.
The return function leaves the state unchanged, while >>= uses the final state of the first computation as the initial state of the second.
Minimal definition is either both of get and put or just state
Evaluate a state computation with the given initial state and return the final value, discarding the final state.
Evaluate a state computation with the given initial state and return the final value, discarding the final state.
Evaluate a state computation with the given initial state and return the final state, discarding the final value.
Evaluate a state computation with the given initial state and return the final state, discarding the final value.
Map both the return value and final state of a computation using the given function.
Map both the return value and final state of a computation using the given function.
Unwrap a state monad computation as a function. (The inverse of state.)
withState f m executes action m on a state modified by applying f.
withStateT f m executes action m on a state modified by applying f.