Forsp is a hybrid language combining Forth and Lisp.
Forsp is a minimalist language.
Forsp has:
- An S-Expression syntax like Lisp
- Function abstraction like Lisp
- Function application like Forth
- An environment structure like Lisp
- Lexically-scoped closures like Lisp (Scheme)
- Cons-cells / lists / atoms like Lisp
- A value/operand stack like Forth
- An ability to express the Lambda Calculus
- A Call-By-Push-Value evaluation order
- Only 3 syntax special forms: ' ^ $
- Only 1 eval-time special form: quote
- Only 10 primitive functions need to self-implement
- Ability to self-implement in very little code
See blog post for details: Forsp: A Forth+Lisp Hybrid Lambda Calculus Language
The best way to learn Forsp is to read the tutorial
(
($x x) $force
(force cswap $_ force) $if
($f $t $c $fn ^f ^t ^c fn) $endif
; Y-Combinator
($f
($x (^x x) f)
($x (^x x) f)
force
) $Y
; rec: syntax sugar for applying the Y-Combinator
($g (^g Y)) $rec
; factorial
($self $n
^if (^n 0 eq 1)
(^n 1 - self ^n *)
endif
) rec $factorial
5 factorial print
)
; compute [$comp $stack $env -> $stack]
($compute $eval
^if (dup is-nil) (rot $_ $_) ( ; false case: return $stack
stack-pop
^if (dup 'quote eq)
($_ stack-pop rot swap stack-push swap ^eval compute)
(swap $comp eval ^comp ^eval compute) endif
) endif
) rec $compute
; eval: [$expr $stack $env -> $stack $env]
($eval
^if (dup is-atom) (
over2 swap env-find dup $callable
^if (dup is-closure) (swap $stack cdr unpack-closure ^stack swap ^eval compute)
(^if (dup is-clos) (force)
(stack-push) endif) endif)
(^if (dup is-list)
(over2 swap make-closure stack-push)
(stack-push) endif) endif
) rec $eval
Building:
./build.sh
NOTE: Only tested on Mac M1
Examples:
./forsp examples/tutorial.fp
./forsp examples/demo.fp
./forsp examples/factorial.fp
./forsp examples/currying.fp
./forsp examples/church-numerals.fp
./forsp examples/higher-order-functions.fp
./forsp examples/church-numerals.fp
./forsp examples/low-level.fp
./forsp examples/fibonacci-imperative.fp
./forsp examples/fibonacci-functional.fp
./forsp examples/forsp.fp