com.github.minlywang.dsl.calc.main.Calculator.java Source code

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Here is the source code for com.github.minlywang.dsl.calc.main.Calculator.java

Source

/**
 * Copyright (c) 2014 Jake Wang
 * https://github.com/minlywang/calc
 *
 * Licensed under MIT
 * http://www.opensource.org/licenses/mit-license.php
 */
package com.github.minlywang.dsl.calc.main;

import java.io.FileInputStream;
import java.io.InputStream;

import org.antlr.v4.runtime.ANTLRInputStream;
import org.antlr.v4.runtime.CommonTokenStream;
import org.antlr.v4.runtime.tree.ParseTree;

import com.github.minlywang.dsl.calc.CalcLexer;
import com.github.minlywang.dsl.calc.CalcParser;
import com.github.minlywang.dsl.calc.Evaluator;

/**
 * Calculator
 * 
 * @author minlywang@foxmail.com
 * @since Apr 5, 2014
 * 
 */
public class Calculator {
    public static void main(String[] args) throws Exception {
        String inputFile = null;
        if (args.length > 0)
            inputFile = args[0];
        InputStream is = System.in;
        if (inputFile != null)
            is = new FileInputStream(inputFile);
        else {
            printStatement();
        }
        ANTLRInputStream input = new ANTLRInputStream(is);
        CalcLexer lexer = new CalcLexer(input);
        CommonTokenStream tokens = new CommonTokenStream(lexer);
        CalcParser parser = new CalcParser(tokens);
        ParseTree tree = parser.compilationUnit(); // parse

        Evaluator eval = new Evaluator();
        eval.visit(tree);
    }

    private static void printStatement() {
        System.out.println();
        System.out.println("/**");
        System.out.println(" * ");
        System.out.println(" * Copyright (c) 2014 Jake Wang");
        System.out.println(" * https://github.com/minlywang/calc");
        System.out.println(" * ");
        System.out.println(" * Licensed under MIT");
        System.out.println(" * http://www.opensource.org/licenses/mit-license.php");
        System.out.println(" * ");
        System.out.println(" * This is a toy language.");
        System.out.println(" * ");
        System.out.println(" * ");
        System.out.println(" */");
        System.out.println();
    }
}