Introduction to Logo Turtle

LogoTurtle is currently the FIRST and 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

• v0.0.11: Turtle Programming: While Loop, Do/Else Loop and Unit Tests Added
• v0.0.10: Turtle Programming: Fractal Stars, Random, Console, Eraser, SetPC, SetXY, Examples, Wait, Bug Fixes and So much more!
• v0.0.9: Turtle Programming v0.0.9: Add SetX, SetY, Square and Rect!
• v0.0.8: Turtle Programming v0.0.8: /* */ comments, dotxy, and javascript!
• v0.0.7: Turtle Programming v0.0.7: Functions with Parameters + Recursion!
• v0.0.6: Turtle Programming v0.0.6: Adding Circle, MoveTo, Turn and Screen!
• v0.0.5: Turtle Programming v0.0.5: Adding IF/ELSE and STOP!
• v0.0.4: LogoTurtle: Make Variables and Comments
• 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

v0.0.12 New Features

This Commit has the following changes:

1. Add Powerful For
2. Add INC to increment a variable
3. Add DEC to decrement a variable
4. StackOverFlow Max Depth set to 1024
5. Add Aliases: SetColor = SetPC, SetH = Turn
6. Add Clear that clears all functions and variables.
7. Export LogoParser and LogoCanvas to NPM: https://www.npmjs.com/package/logoturtle

Screenshots

For in LOGO can be used in a few ways:

• FOR [START STOP] [CODE]
• FOR [START STOP STEP] [CODE]
• FOR [VARIABLE START STOP] [CODE]
• FOR [VARIABLE START STOP STEP] [CODE]

For example,

ht cs for [i 0 360 45] [seth :i make "n 0 
  repeat 80 [setpc :random*15 
    repeat 8 [fd :n rt 45] inc :n
  ] 
]

Implement the FOR Loop in Javascript for LOGO

case "for":
    if (word_next != '[') {
        this.pushErr(word, LOGO_ERR_MISSING_LEFT, word_next);
    }               
    find_next_body = getNextBody(s, i, U);
    if (find_next_body.right >= U) {
        this.pushErr(word, LOGO_ERR_MISSING_RIGHT);
        return false;
    }
    let for_code = s.substring(find_next_body.left + 1, find_next_body.right).trim();
    i = find_next_body.right + 1;
    let for_body = getNextBody(s, i, U);
    if (for_body.right >= U) {
        this.pushErr(word, LOGO_ERR_MISSING_RIGHT);
        return false;
    }                   
    let for_code2 = s.substring(for_body.left + 1, for_body.right).trim();
    if ((for_code.length > 0) && (for_code2.length > 0)) {
        // remove surrounding white spaces
        let for_code_arr = for_code.split(' ').map(item => item.trim()).filter(x => x != '');
        // For Syntax: [VarName Start Stop Step]
        let for_index = 0;
        let for_var = "";
        let saved_for_var = null;
        if (isValidVarName(for_code_arr[0])) {
            for_var = for_code_arr[0];
            if (for_var in this.vars) {
                saved_for_var = this.vars[for_var];
            }                           
            this.vars[for_var] = 0;
            for_index ++;
        }
        if (for_code_arr.length - for_index < 2) {
            this.pushErr(word, LOGO_ERR_INVALID_FOR);
            return false;
        }
        if (for_code_arr.length - for_index > 3) {
            this.pushErr(word, LOGO_ERR_INVALID_FOR);
            return false;
        }                       
        let for_start = this.evalVars(for_code_arr[for_index]);
        let for_stop = this.evalVars(for_code_arr[for_index + 1]);
        let for_step = 1;
        if (for_index + 2 < for_code_arr.length) {
            for_step = this.evalVars(for_code_arr[for_index + 2]);
        }
        if ((for_start === '') || (!isNumeric(for_start))) {
            this.pushErr(word, LOGO_ERR_MISSING_NUMBERS, for_start);
            return false;
        }       
        if ((for_stop === '') || (!isNumeric(for_stop))) {
            this.pushErr(word, LOGO_ERR_MISSING_NUMBERS, for_stop);
            return false;
        }   
        if ((for_step === '') || (!isNumeric(for_step))) {
            this.pushErr(word, LOGO_ERR_MISSING_NUMBERS, for_step);
            return false;
        }
        // get for values
        for_start = parseInt(for_start);
        for_stop = parseInt(for_stop);
        for_step = parseInt(for_step);
        // beware of endless loop ^_^
        for (let for_loop = for_start; for_loop <= for_stop; for_loop += for_step) {
            if (for_var != "") {
                this.vars[for_var] = for_loop;
            }
            // if body
            if (!this.run(for_code2, 0, for_code2.length, depth + 1)) {     
                return false;
            }                           
        }
        // restore loop variable
        if ((for_var != "") && saved_for_var !== null) {
            this.vars[for_var] = saved_for_var;
        }
    }
    // parse next token
    i = for_body.right + 1;                 
    break;  

Roadmap of Chrome Extension: Logo Turtle

I believe LogoTurtle is more or less in beta now. Therefore, bug Fixes and any suggestions, please shout @justyy

Technology Stack

If an App can be written in Javascript, eventually it will be written in Javascript.

Chrome Webstore

Install the Turtle Programming for Kids Now!

Contribution Welcome

Github: https://github.com/DoctorLai/LogoTurtle

1. Fork it!
2. Create your feature branch: git checkout -b my-new-feature
3. Commit your changes: git commit -am 'Add some feature'
4. Push to the branch: git push origin my-new-feature
5. Submit a pull request.

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Posted on Utopian.io - Rewarding Open Source Contributors

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