parse and evaluate math expressions
src/Numeric | ||
.gitignore | ||
.travis.yml | ||
LICENSE | ||
mathexpr.cabal | ||
README.md | ||
Setup.hs | ||
stack.yaml |
mathexpr ![Travis](https://img.shields.io/travis/mdibaiee/mathexpr.svg)
Ever wanted to take as input a mathematical expression to fill in values and use it? mathexpr
is exactly what you need.
I also wrote this in JavaScript some time ago: Equation
Examples
Simple evaluation of expressions:
import Data.MathExpr
main = do
expr <- getLine -- a mathematical expression, e.g. sin x + y ^ 2
-- replace x and y with the specified values and evaluate: sin 2 + 5 ^ 2 = 25.909..
print $ evaluate def expr [("x", 2), ("y", 5)]
Using custom operators and functions:
import Data.MathExpr
-- operators are in the form (character, precedence, function)
-- example: ('+', 0, (+)), ('*', 1, (*))
-- the function should have the type (Double -> Double -> Double)
-- the higher the precedence, the sooner the operator operates
-- functions are in the form (name, function)
-- example: ("ln", log)
-- the function should have the type (Double -> Double)
main =
let avg a b = (a + b) / 2
let settings = Settings { operators = defaultOperators ++ [('~', 0, avg)]
, functions = defaultFunctions ++ [("trunc", fromIntegral . truncate)]
evaluate settings "3 ~ 5" [] -- 4
evaluate settings "trunc 1.1" [] -- 1