Calculator Tool

Installation

Install peer dependencies:

npm i expr-eval

Copy the code

Add the following code to your utils/calculatorTool.ts file:

calculatorTool.ts

import { Parser } from "expr-eval";
 
export class CalculatorTool {
  async evaluate(input: string): Promise<string> {
    try {
      return Parser.evaluate(input).toString();
    } catch (error) {
      console.error("Error calculating expression:", error);
      return "Error Calculating Expression";
    }
  }
 
  async evaluateMultiVar(
    expression: string,
    variables: Record<string, number>
  ): Promise<string> {
    try {
      const substitutedExpression = this.substituteVariables(
        expression,
        variables
      );
      return Parser.evaluate(substitutedExpression).toString();
    } catch (error) {
      console.error("Error evaluating multi-variable expression:", error);
      return "Error evaluating expression";
    }
  }
 
  private substituteVariables(
    expression: string,
    variables: Record<string, number>
  ): string {
    Object.entries(variables).forEach(([variable, value]) => {
      expression = expression.replace(
        new RegExp(variable, "g"),
        value.toString()
      );
    });
    return expression;
  }
}

Usage

import { CalculatorTool } from "@/utils/calculatorTool";
 
 const calculator = new CalculatorTool();
 
 //for simple expressions
  const simpleExpression = "2 * (3 + 4) - 100 / (99 - 1)";
  const simpleResult = await calculator.evaluate(simpleExpression);
 
  // For complex expressions
  const complexExpression = "2 * (a + b) - 100 / (c - 1)";
  const variables = { a: 3, b: 4, c: 99 };
 
  const complexResult = await calculator.evaluateMultiVar(
    complexExpression,
    variables
  );
  console.log( "Simple Result: ", simpleResult, "Complex Result : ", complexResult);
 
/**
 Simple Result:  12.979591836734693 Complex Result :  12.979591836734693
**/

Props

evaluate

Prop	Type	Description
input	string	The mathematical input string.

evaluateMultiVar

Prop	Type	Description
expression	string	The mathematical input expression.
variables		Variables of the mathematical expression.

Credits

This component is built on top of Langchain's Calculator Tool