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Finch is a simple bytecode interpreted, purely object-oriented, prototype-based, dynamically-typed programming language. It's mostly inspired by Smalltalk, Self, and Javascript.

It is written in C++ with a hand-written lexer and parser. It has minimal dependencies. I want Finch to be:

  • Syntactically expressive yet minimal. Your code should look beautiful and do what you want.

  • An example of a small, clean C++ codebase for an interpreter. If you can read C++ and want to learn more about programming languages, I hope Finch's code will be a good primer.

  • A language in the Smalltalk family that's friendly to people coming from a text file and curly brace background.

  • A minimal prototype-based dynamic language. I think prototypes are a really cool paradigm, but Self goes too far, and Javascript doesn't go far enough.

  • Easily embeddable in other applications. I don't know if Finch ever will have real use, but if it does, it will likely be as a configuration or scripting language within a larger application, much like Lua.

A Taste of the Language

Here's a little example to get you going. This little program doesn't draw, but it will tell you what turns to make to draw a dragon curve:

// create an object and put it in a variable "dragon"
dragon <- [
  // define a "trace:" method for outputting the series of left and
  // right turns needed to draw a dragon curve.
  trace: depth {
    self traceDepth: depth turn: "R"
    writeLine: "" // end the line

  // the main recursive method
  traceDepth: n turn: turn {
    if: n > 0 then: {
      self traceDepth: n - 1 turn: "R"
      write: turn
      self traceDepth: n - 1 turn: "L"

// now lets try it
dragon trace: 5

Getting Started

Finch lives on github here:

To play around with it, sync it down. Finch uses GYP to generate projects or makefiles for your platform, which you then build to get an executable.

  1. Download GYP from:
  2. Clone the finch repo from github.
  3. In a terminal/command prompt, navigate to the root finch/ directory.
  4. Run GYP on this file: <path to gyp>/gyp --depth=1 Where <path to gyp> is wherever you downloaded GYP to in step 1. This should spit out a project/makefile in the root directory for your platform.
  5. Open that project in XCode or VS and build, or build the makefile.
  6. Ta-da! You should now have a Finch executable under a build/ directory.

Let me know if you run into any problems.

Running Finch

Once you've got it built and running, you'll be at the main interpreter prompt. Finch is a command-line app. If you run it without any arguments, it drops you into a REPL, an interactive session. You can type in chunks of code and it will interpret them immediately. (If you run it with a single argument, it expects that to be a path to a .fin script, and it will load and run that script.)

Once you're in the REPL, you can load and execute a script using load:. The path must be relative to where the executable is right now (lame!). You can run the tests like this:

>> load: "../../test/test.fin"

Where to Go from Here

You should be good to start hacking some Finch code now. There is some documentation here:

If you have any questions or comments, holler at me.


The Finch programming language






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