Where Would I Even Start?: Compilers

This repository contains a simple interpreter for algebraic expressions, built to demonstrate some core compiler concepts. This is a companion to the blog post I wrote on Compilers. The entire codebase is just over 300 lines.

This interpreter is capable of parsing expressions including any combination of the 4 basic mathematic operators (+, -, *, /), and assignments to variables. Operands for the operators may only be integer values or variable references. For example, the following is a valid program:

@a = 2 + 2
@b = 1 + 3 * 3
@c = b / a

For simplicity, running a program will print out the stack contents and the symbol table after execution. For the above, this would appear as:

Stack contents: []
Variables:
    a = 4
    b = 10
    c = 2.5

Installation

You will need Crystal installed, which can easily be done on the command line. Installing with brew is as simple as running brew install:

brew install crystal-lang

Installing on linux depends on your distribution, so check the installation guide for more information.

With Crystal installed, getting this project installed is as simple as a git clone:

git clone https://github.com/faultyserver/compilers-intro

Usage

With the project installed locally, running the interpreter is as simple as running crystal run:

crystal run src/runner.cr

You can also build a standalone binary to run at anytime with crystal build:

crystal build src/runner.cr
# Then later on, run it
./runner

To change the input to the interpreter, edit the string passed to Parser.new in runner.cr, then rerun/rebuild.

Development

I don't expect this repository to change much, as it is just demonstrating initial concepts.

Contributing

1. Fork it ( https://github.com/faultyserver/compilers-intro/fork )
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. Create a new Pull Request

Contributors

• faultyserver Jon Egeland - creator, maintainer