Slogo: A programming language with a healthy dose of slugs

Introduction
Abstract
Syntax
License
Try It

# Slogo

Slogo is a [context-free grammar](https://en.wikipedia.org/wiki/Context_free_grammar)
which leverages several existing Javascript libraries.

Most notable of these libraries are:

* [Jison](#jison) - a parser generator
* [WebGL](#webgl) - a 3d graphics specification

# Jison

Slogo makes use of the [Jison](https://github.com/zaach/jison)
Javascript library to simplify the process of defining a formal grammar.  Jison
takes a context-free grammar as input and produces a javascript file capable of
parsing the specified grammar.

Jison has modes to recognize languages described by the following grammars:

* [LALR(1)](https://en.wikipedia.org/wiki/LALR_parser)
* [LR(0)](https://en.wikipedia.org/wiki/LR_parser)
* [SLR(1)](https://en.wikipedia.org/wiki/SLR_grammar)
* [LR(1)](https://en.wikipedia.org/wiki/Canonical_LR_parser) _canonical LR parsers_

It also has a special mode for generating
[LL(1)](https://en.wikipedia.org/wiki/LL_parser) parse tables

> ## Bison
>
> Jison is modeled after [Bison](https://www.gnu.org/software/bison/) a parser
> generator for the C progamming language.  Bison is a parser generator that
> converts an annotated context-free grammar into an LALR(1) or
> [GLR](https://en.wikipedia.org/wiki/Glr_parser) parser for that grammar.

# WebGL

[WebGL](https://en.wikipedia.org/wiki/WebGL) is a recently released specification
for modern browsers.  It extends Javascript with the ability to generate 3D
graphics.  WebGL enables the creation of hardware-accelerated graphics as it
communicates directly to the <abbr title="Graphics Processing Unit">GPU</abbr>
on the host computer.

Slogo makes use of Jison's ability to share the scope of a grammar with other
parts of Javascript via the [`yy` variable](https://zaach.github.com/jison/docs/#sharing-scope).
When a Slogo program is parsed it makes direct calls to WebGL via the Slogo
graphics framework.

# Slogo Syntax
Since Slogo compiles down to Javascript we borrow some functionality however the
syntax is more like Lisp or Ruby.

* [Math constants and functions](#mathconstantsandfunctions)
* [Bitwise Operations](#bitwiseoperators)

## Math constants and functions
The [Mozilla Developer Network documentation](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Math)
for Javascript's Math object is worth looking up because we retain many of
Javascript's math constants and functions.

In regards to math the syntax of Slogo differs from Javascript in a
number of ways.  Namely one design consideration is that math functions are
first class citizens in Slogo.  The idea is that we're here to do math primarily
and develop code secondarily.

1. In Slogo every math constant and function is directly available in
  the main namespace.

PI # returns 3.141592653589793

max 2, 5, 3 # returns 5

2. Exponents have their own operator, the `^` operator

3 ^ 2 # returns 9

3. Factorials have their own operator, the `!` operator

4! # returns 4 * 3 * 2 * 1

4. The percent sign is used for percentages.

50% # returns 0.50

5. The [`modulus`](https://en.wikipedia.org/wiki/Modulo_operation) operator is 
    still an operator but it has a longer name

3 mod 2 # returns 1

## Bitwise operators
We have four bitwise operators in Slogo.  Bitwise operators allow for the
comparison of boolean values.

_Note: If you're familiar with how bitwise operations work in other languages
feel free to skip to the next section._

### And operator
    true and true   # returns true
    true and false  # returns false
    false and false # returns false
    false and true  # returns false

### Or operator
    true or true   # returns true
    true or false  # returns true
    false or false # returns false
    false or true  # returns true

### Xor operator (exclusive or)
    true xor true   # returns false
    true xor false  # returns true
    false xor false # returns false
    false xor true  # returns true

### Not operator
    true not true   # returns true
    true not false  # returns false
    false not false # returns false
    false not true  # returns true

## Blocks

Blocks also known as functions exist in several different forms in Slogo we
eschew the purely imperative approach of Javascript and provide some helpers for
blocks.  Blocks return their last statement by default.

### Block Examples

to add |a, b|
      a + b
    end

### Anonymous Blocks

to bind |func, scope|
      to
        func.apply(scope, arguments)
      end
    end

### Closures

Closures build on the idea of blocks.  Using closures we can bind the scope of a
function to a particular object

to run
      @motivation
    end

more = {
      motivation: 'Yes!'
    }

do run(more) # returns 'Yes!'

# License agreement

Slogo is **free** software released under the MIT user license.  The MIT user
license is the most permissive license out there.
 
> Copyright (c) 2011 Hans Oksendahl
> 
> Permission is hereby granted, free of charge, to any person
> obtaining a copy of this software and associated documentation
> files (the "Software"), to deal in the Software without
> restriction, including without limitation the rights to use,
> copy, modify, merge, publish, distribute, sublicense, and/or sell
> copies of the Software, and to permit persons to whom the
> Software is furnished to do so, subject to the following
> conditions:
> 
> The above copyright notice and this permission notice shall be
> included in all copies or substantial portions of the Software.
>
> You must not take yourself too seriously.
> 
> THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
> EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
> OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
> NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
> HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
> WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> OTHER DEALINGS IN THE SOFTWARE.