A mathematical expression library written in F# language

The parser can parse about any mathematical expression and evaluate the result, including static variables and custom functions.

The parser is hand written using regular expressions (yes, I solved two problems ;) and simple string parsing. I wanted to do this without lexers and any stuff like that.

Usage

Simple expressions

open FCalculator.Evaluator

let result = EvaluateExpression "1 + 2 * 3"

Variables and functions

open FCalculator.Evaluator

let myFuncs = [ ("multiply", fun (args:obj list) -> (unbox args.[0]) * (unbox args.[1])) ] |> Map.ofList
let myVars = [ ("x", box 4); ("y", box 2) ] |> Map.ofList

let result = EvaluateExpressionWithFunctionsAndVariables myFuncs myVars "multiply(x, y)"

Function and variable names are always case sensitive.

Parsing without evaluating

open FCalculator.Parser

let topNode = ParseExpression "1 * (2 + 2) / 4" 

Bugs

There is no error handling. You might get a SyntaxError exception but they're thrown only because something needs to be returned in those cases.

Why?

This was my first touch to functional programming and I thought that writing a string parser and evaluating expression trees would be a fun exercise. And it was.