ALisp

A Lisp implementation in C++ 14 (alisp) and Node.js (alisp.js).

What?

A Lisp interpreter that focuses on speed and minimizing memory usage.

The C++ version is written in C++ 14 and implements the copy-and-swap idiom to avoid memory leaks and lifetime issues.

The Node.js version is written to be compatible with the C++ version, and code should run on either version without issue.

Why?

Scheme is all well and fun, but using a string for the main data type results in constant parsing/unparsing, and large memory usage for small types. Additionally, since each Scheme cell (in our implementation) has all possible data types, each Cell requires a lot of setup/teardown and memory.

Our Lisp implementation specialises the data types, so each Cell takes only the memory needed for its type.

How (to build)?

• C++ version:

  • NetBeans 8+: This repository is also a NetBeans project. The project was created with NetBeans 8.2 and older versions of NetBeans may not work with it.

  • On Linux:

    • Standard compile: make CONF=Release

    • Cross Platform OpenRISC: make CONF=Release CND_PLATFORM=or1000 CXX=or1k-linux-musl-g++

    • Look for alisp in dist/configuration/platform/

      • Where configuration is one of Debug or Release

      • Where platform is the Makefile platform, either Cygwin_x86_64-Windows or or1000. This platform name was automatically generated by NetBeans IDE, and may not reflect your actual platform.

  • Visual Studio:

    • Open alisp.vcxproj and compile.

    • Look for alisp.exe in the Debug or Release directories.

• Node.js version:

  • In any console run: node index [options]

  • Try running the debug evaluator in itself:

    • node index seval.lisp -s -t seval.lisp fac.lisp

      • The -s switch silences the debugging output of one of the seval instances.

      • The -t switch enables tail recursion

Pass --help on the command line for information on commandline options.

See the lisp directory for samples than can be run.

Useful Resources

The following resources were invaluable in overcoming the many obstacles C++ likes to put in your way:

• The C++ slicing problem - avoiding object slicing using smart pointers

• GCC not catching exceptions - why your catch clauses aren't catching under gcc

History

(Some versions not in separate commits)

• (Alisp.js 0.2.4 Platform0.4) - Added "next" feature (transition control to given function without creating new environment); added fastmacro feature (use an environment created at declaration not runtime); seval.lisp updated with new features

• 0.68.9 - Platform 0.3 implemented for Node.js. Contains an evaluator written in alisp, and more sample code.

• 0.67 - Fixed macros not running, set! misbehaving (throwing exceptions), added a number of platform functions; added Node.js version of interpreter and platform.

• 0.66 - Add runtime bounds/arguments checking; StringCell has ListCell-like behaviours; memory leak fixed; added linenoise-ng; split into new repo

• 0.60 - Add timekeeping; debugging, parsing, and evaluation functions; load file specified on command line and execute

• 0.50 - Add standard library of functions; command line parsing; StringTypeCell attempts to parse into number values

• 0.40 - Added REPL, exception handling

• 0.32 - Working eval loop, parsing; G++ fixes; Makefile included

• 0.22 - G++ fixes. Now compiles under G++ using std=c++14. Valgrind reports no memory leaks.

• 0.2 - Working prototype. Cell type completely rewritten.

• 0.1 - Prototype