LogoTurtle: Make Variables and Comments

justyy(74)

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#utopian-io

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Introduction to Logo Turtle

LogoTurtle is the first and currently only one Chrome Extension for Turtle Graphics. I have also written a PHP version of Logo Interpreter in 2006 but that runs only on the server.

Previous Contributions

v0.0.3: Turtle Graphics Programming Update: Adding text, jump, dot, fontsize, download as png
v0.0.2: LogoTurtle v0.0.2: ShowTurtle, HideTurtle, Color, Width and Help.
Teach Your Kids Programming - The First Logo Interpreter (Turtle Graphics) in Chrome Extension!
v0.0.1

v0.0.4 New Features

This Commit supports the Make command which declares a variable in LOGO programming. Also, a single line comment starts with a semi-colon.

Screenshots

With variable support, you'll see how powerful the turtle is.

How to Store Variables in Javascript for Logo Turtle?

We use the dictionary to store a global key-pair values for variables. In future versions, it will be improved to support variables of different scopes.

Getter and Setter:

    // push a varaible
    addVar(name, value) {
        this.vars[name] = this.evalVars(value);
    }

    // find a variable
    getVar(name) {
        if (name in this.vars) {
            return this.vars[name];
        }
        return null;
    }

To evaluate the value of a expression:

    // eval variables
    evalVars(s) {
        let var_arr = parseVarName(s);
        let varlen = var_arr.length;
        for (let i = 0; i < varlen; ++ i) {
            let var_name = var_arr[i].substring(1);         
            let local = this.getVar(var_name);
            if (local) {                    
                s = s.replaceAll(":" + var_name, local);
                break;
            }
        }
        return s;
    }

where the parseVarName looks for :var

// parse var name
const parseVarName = (s) => {
    let pat = /(:[a-zA-Z]+[a-zA-Z0-9]*)/g;
    let arr = [];
    let matches;
    while (matches = pat.exec(s)) {
        arr.push(matches[1]);       
    }
    return arr;
}