SMEI (Simple Math Expression Interpreter)

Tree-walk interpreter used to evaluate basic math expressions

Motivation

The main goal is to create simple and easy to use math expression interpreter that can be used in any application that performs (for now) simple mathematical operations.

Includes

Lexer - (or Scanner) converts raw string input into an array of tokens.

Parser - converts tokens into AST.

Interpreter - evaluates each tree node from bottom-up leading to result

Install

You can install get-good-readme by entering this command
npm install --save smei

Usage

import smei from 'smei';

const result = smei.eval('2+3*4'); // 14

If you want you can access token array or ast using core classes.

import { Lexer, Parser, Interpreter } from 'smei';

const source = '2+3*4';

const lexer = new Lexer({ source });
/**
 * Tokens:
 * Token { type: "NUMBER", lexeme: "2", line: 1 }
 * Token { type: "PLUS", lexeme: "+", line: 1 }
 * Token { type: "NUMBER", lexeme: "3", line: 1 }
 * Token { type: "STAR", lexeme: "*", line: 1 }
 * Token { type: "NUMBER", lexeme: "4", line: 1 }
 * Token { type: "EOF", lexeme: "", line: 1 }
 */
const tokens = lexer.tokenize();

const parser = new Parser(tokens);
// Abstract syntax tree
const ast = parser.parse();

const interpreter = new Interpreter();

const result = interpreter.evaluate(ast); // 14

Todo

• Working with scientific notation (eg. 1e+10 + 1e+6)
• Working with big numbers
• Using strings as function arguments

Sources:

Crafting interpreters