HAL

A lisp interpreter in Haskell based on r6rs

By @skyf0l and @pebloop

Notes

Category	Percentage	Tests
01 Basics	100%	3/3
02 Quote	100%	2/2
03 Cons Car Cdr	100%	5/5
04 Arithmetics	100%	3/3
05 Equalities	100%	5/5
06 Define	100%	2/2
07 Conditionals	100%	3/3
08 Lambda	100%	3/3
09 Complex programs	100%	5/5
10 Error handling	100%	4/4
99 Coding style	100%	3/3
End scores	100%	38/38

Features

• Builtins
  • Basics (car, cdr, cons, void, ...)
  • Predicates (eq?, null?, number?, pair?, ...)
  • Arithmetic (+, -, *, div, mod, min, max, even?, odd?, pow, sum, product, ...)
  • Comparisons (<, >, <=, >=)
  • String comparison (string=?, string<?, string<=?, string>?, string>=?)
  • List functions (length, append, reverse, map, filter, foldl, foldr, ...)
  • Algorithms (fibonacci, factorial, merge-sort)
  • IO (display, newline)
  • Load library (load)
• Forms
  • Cond
  • If
  • Let
  • Lambda
  • Quote
  • Set
  • Define
  • Begin
• REPL
  • Read-eval-print loop (interactive)
  • Debug commands (show expression in datums / forms)
  • Environment commands (show, enter, leave, clear)

Usage

$ ./hal --help
Usage: ./hal [FILE]... [OPTION]...
  -h                --help                   Show this help and exit
  -q                --quiet                  Suppress prompt
  -i                --interactive            Enable interactive mode
  -l FILE/DIR PATH  --library=FILE/DIR PATH  Add a library path

Demo

$ ./hal
HAL - Lisp REPL
Type :h to see help
Type :q to quit

> (define add (lambda (a b) (+ a b)))
> add
#<procedure>
> (add 40 2)
42
> (set! add 42)
> add
42
> (fib 21)
10946
> (merge-sort '(39 16 22 24 17 29 18 26 27 3 34 25 10 6 7 12 8 30 2 21 13 36 14 38 32 41 40 4 35 19 5 33 23 9 15 31 28 20 42 37 11 1))
(1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42)

Build

$ make

or

$ stack build --copy-bins

Tests

$ make tests_run

or

$ ./tests.sh