benjaminphi5/propositional-logic-parser

A parser that checks human readable equaltions, builds a structure form them, can query them for true/false values and can print them out

Propositional-Logic-Parser

A parser that checks human readable equations, builds a structure form them, can query them for true/false values and can print them out in human readable form.

The challenge for me was implementing it in a functional style in ML.

It takes in input such as inputString "!a&b|c<->!d"; Turns this into its abstract syntax tree: > val it = [Prop (Iff (Or (And (Not (Lit "a"), Lit "b"), Lit "c"), Not (Lit "d")))]: builder list

And then can for example, convert it back to a string, convert it to NNF etc:

> outputProposition it;

proposition: (!a & b) | c <-> !d

val it = (): ?.unit

In NNF:

> convertToNNF (inputString "!a&b|c<->!d"); val it = And (Or (Not (Or (And (Not ..., Lit "b"), Lit "c")), Not (Lit "d")), Or (Not (Not (Lit "d")), Or (And (Not (Lit "a"), Lit "b"), Lit "c"))): prop > printout it; `proposition: (!((!a & b) | c) | !d) & (!d | (!a & b) | c)` val it = (): ?.unit

If you were to implement an incorrect function, that has say unbalanced/incorrectly placed brackets or an incorrect symbol, you would get and exception:

> inputString "(a&)(b"; Exception- malformedInput raised