Skip to content

Latest commit

 

History

History
executable file
·
75 lines (61 loc) · 2.88 KB

README.md

File metadata and controls

executable file
·
75 lines (61 loc) · 2.88 KB
Raw

Mathematical expressions evaluator

Overview

Implementation of mathematical expressions evaluator in Scala. Supported operations and expressions:

  • Addition (+)
  • Subtraction (-)
  • Multiplication (*)
  • Division (/)
  • Unary minus
  • Parentheses

Set up

Add dependency to your project (currently there is only version for Scala 2.11):

libraryDependencies += "com.github.pdorobisz" %% "math-expression-evaluator" % "1.0.0"

Usage

Evaluating expressions

com.github.pdorobisz.mathexpressionevaluator.Evaluator.evaluate takes string representing expression in infix notation (may contain spaces) and returns evaluation result as Validation from Scalaz:

import com.github.pdorobisz.mathexpressionevaluator.Evaluator
import com.github.pdorobisz.mathexpressionevaluator.errors.EvaluatorError
import spire.math.Rational
import scalaz.Validation

val result: Validation[EvaluatorError, Rational] = Evaluator.evaluate("1+2*3")

EvaluatorError contains position at which evaluation error has occurred. Rational (from Spire) represents evaluated value.

Some examples:

import com.github.pdorobisz.mathexpressionevaluator.Evaluator

println(Evaluator.evaluate("1+2*3"))         // Success(7)
println(Evaluator.evaluate("4 / (2*3 + 2)")) // Success(1/2)
println(Evaluator.evaluate("4/(1-1)"))       // Failure(DivideByZero(1))
println(Evaluator.evaluate("2*(3+4"))        // Failure(ParenthesisNotMatched(2))

Converting expressions to postfix form (Reverse Polish Notation)

As a part of evaluation process expression is converted to Reverse Polish Notation. It is possible to get expression converted to this form instead of evaluated value:

import com.github.pdorobisz.mathexpressionevaluator.errors.EvaluatorError
import com.github.pdorobisz.mathexpressionevaluator.tokens.TokenPosition
import com.github.pdorobisz.mathexpressionevaluator.utils.RPNConverter
import scalaz.Validation

val result: Validation[EvaluatorError, Seq[TokenPosition]] = RPNConverter.convert("(3+7)*2")
println(result) // Success(List(TokenPosition(1,Value(3)), TokenPosition(3,Value(7)), TokenPosition(2,Operator(Addition)), TokenPosition(6,Value(2)), TokenPosition(5,Operator(Multiplication))))

Evaluating expressions in postfix form (Reverse Polish Notation)

import com.github.pdorobisz.mathexpressionevaluator.tokens.TokenFactory._
import com.github.pdorobisz.mathexpressionevaluator.utils.RPNEvaluator

val rpn = Seq(value(1, 2), value(3, 3), addition(2), value(6, 5), multiplication(5)) // (2+3)*5
println(RPNEvaluator.evaluate(rpn))

Implicit conversions

To make your life easier you can use implicit conversions to add new methods:

import com.github.pdorobisz.mathexpressionevaluator.utils.EvaluatorImplicits._

val rpnForm = "3+5*6".toRPN
val evaluationResult= "3+5*6".evaluateExpression