hal

A Scheme interpreter in Haskell.

Features

• Macro definitions with define-syntax and syntax-rules
• A bare bones standard library
• Syntax error messages with line and column numbers
• Continuations with call/cc
• Multiple values with values
• Exact integers, rationals and floating point numbers
• REPL with multi-line support

Builtins and standard library

Name	Kind
-	procedure
*	procedure
/	procedure
+	procedure
<	procedure
<=	procedure
=	procedure
>	procedure
>=	procedure
abs	procedure
and	syntax
append	procedure
apply	procedure
atom?	procedure
begin	syntax
boolean?	procedure
call-with-values	procedure
call/cc	procedure
car .. caaaar	procedure
case	syntax
cdr .. cddddr	procedure
char?	procedure
complex?	procedure
cond	syntax
cons*	procedure
cons	procedure
define-syntax	syntax
define	syntax
display	procedure
div	procedure
dump-heap	procedure
eq?	procedure
equal?*	procedure
eqv?*	procedure
error*	procedure
even?	procedure
exact?	procedure
expand	procedure
filter	procedure
fold-left	procedure
fold-right	procedure
if	syntax
inexact?	procedure
lambda	syntax
let*	syntax
let	syntax
letrec*	syntax
letrec*	syntax
list	procedure
map	procedure
max	procedure
min	procedure
mod	procedure
negative?	procedure
newline	procedure
not	procedure
null?	procedure
number?	procedure
odd?	procedure
or	syntax
pair?	procedure
positive?	procedure
quote	syntax
rational?	procedure
real?	procedure
set!	syntax
string?	procedure
symbol?	procedure
syntax-rules*	syntax
values	procedure
void	procedure
zero?	procedure

*implementation not fully compliant with the r6rs standard.

Installation

Make sure stack is installed, then run:

stack install hal

This will generate a hal executable in the current directory.

Usage

hal [FILES...] [-i]

• FILES: files to run
• -i: interactive mode (implied when no files are given)

The global environment is initialized with the standard library before running the first file and is not cleared after running each file. That means all files are run as if they were one single top-level program. After running all files, the value of the last expression of the last file is displayed.

Examples

See the examples directory.