| Safe Haskell | Safe |
|---|---|
| Language | Haskell2010 |
Data.Turing
Description
This module defines everything required to simulate a simple deterministic
Turing machine. There are several equivalent but slightly different
definitions of Turing machines in use - ours has the machine write and
move in each step of execution. In addition, we allow a special movement
DontMove that results in just a write operation.
- data TuringMachine s q
- mkTuringMachine :: TransitionFunction s q -> q -> [q] -> TuringMachine s q
- data Movement
- type TransitionFunction s q = (q, Maybe s) -> Maybe (q, Maybe s, Movement)
- data MachineResult
- run :: Eq q => TuringMachine s q -> [s] -> MachineResult
- runFor :: (Integral i, Eq q) => i -> TuringMachine s q -> [s] -> Maybe MachineResult
The Turing machine
data TuringMachine s q Source
Abstract type representing a Turing machine. It is parameterized over
the alphabet and state types. A full definition contains the initial state,
a list of accepting states and the transition function. Construct through
mkTuringMachine.
mkTuringMachine :: TransitionFunction s q -> q -> [q] -> TuringMachine s q Source
Construct a Turing machine from the transition function, its initial state and a list of accepting states.
Associated types
A Turing machine has three options of moving its read head: left, right, or no move at all.
type TransitionFunction s q = (q, Maybe s) -> Maybe (q, Maybe s, Movement) Source
The transition function maps the current state and tape contents
to a triple describing the new state, the value to write to the tape, and
a head movement. If the function is Nothing for the current state
and tape contents, the machine halts.
Running a machine
run :: Eq q => TuringMachine s q -> [s] -> MachineResult Source
Run a machine indefinitely on the given input. If it halts, it either accepts or rejects the input.
runFor :: (Integral i, Eq q) => i -> TuringMachine s q -> [s] -> Maybe MachineResult Source