ptscheme v0.3

Overview

My take on a Scheme dialect LISP implementation realized in 'C' with enough functionality to complete the excercises in the Purple Wizard book, "Structure and Interpretation of Computer Programs"

Current Status

The basic interpreter now functions; however, a standard library has not yet been implemented. Also, there are numerous clean-up tasks and enhancements I would like to complete before calling it a "1.0" version.

Release notes can be found off the project wiki: here.

Getting things running

The following instructions have been tested on OS X v10.10.5. I'm sure they assume that certain dev tools are already installed, but I haven't yet tested from a clean OS to confirm the full set of requirements. Basically, if you have enough to complie C code with clang (Apple's gcc-style compliler), can run 'make', and have git installed you're on your way.

Clone:

$ git clone https://github.com/ptdecker/ptscheme.git
$ cd ptscheme

Build:

$ make

Test (no coverage for now):

$ make clean
$ make
$ make test

NOTE: A more complete set of manual test can be found in './tests/manualtests.txt'

Run:

$ ./ptscheme

The Standard Library

A small standard library is provided that implements common operators including the '/' operator for the quotent function. To load the standard library from within the REPL:

> (load "./libs/stdlib.scm")
ok

Replace the path with the appropriate path for your installation

Implementation notes and credits

Partial compiance with the R5RS standard is attempted, but I have included variations (such as C-style character literals).

This implementation of Scheme draws heavily from the following sources:

• Daniel Holden's "Build Your Own LISP"
• Peter Michaux's "Scheme from Scratch"

The following changes have been made from Michaux:

• Broke apart into logical (hopefully) modules instead of one big source file
• Inclusion of an error type so that malformed input doesn't kill the REPL
• Handled the singleton boolean object type differently to parallel other objects
• Implemented characters using C-style character literals
• Included support for all C-style escape sequences except for octal and hex
• Echoed the way the singleton boolean was handled for singleton empty
• Handled 'quote', 'define', 'set', 'ok', 'if', and lambda symbols as singletons too
• Implemented hash table-based symbol table [O(1)] as opposed to reusing pairs approach [O(n)]
• Avoided goto-based tail recurrsion call approach
• Included an 'exit' primitive
• Extended numeric support to include floating point support (IEEE 754 double precision)