172 lines
4.2 KiB
Plaintext
Executable File
172 lines
4.2 KiB
Plaintext
Executable File
#!/usr/bin/pl
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; Print with a newline
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(def prnl (fn (_txt) (
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(prn _txt)
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(pch 10)
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)))
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; Initialize an empty stack
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(def stack ())
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; Add the given num to the stack
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(def stkadd (fn (a)
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(def stack (pre stack a))))
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; Silently remove the top of the stack
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(def _pop (fn (_)
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(def stack (rest stack))))
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; Remove and return the stack top
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(def bop (fn (_) (
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(def _a (at 0 stack))
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(_pop 0)
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_a
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)))
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; Loud, checked version of _pop
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(def pop (fn (_)
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(if (> (len stack 0) 0) (
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(prn (at 0 stack))
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(_pop 0))
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(prnl "pop: STACK EMPTY")
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)))
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; Takes a two-parameter operation and
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; applies it to the top two stack elements
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(def twop (fn (_op) (
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(if (> (len stack) 1) (
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(def (_b _a) ((bop 0) (bop 0)))
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(stkadd (_op _a _b)))
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(prnl "twop: STACK TOO SMALL")
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))))
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; Define important symbols/functions
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; An annoying hack for right now
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(def . ".")
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(def : ":")
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(def ^ "^")
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(def $ "$")
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(def swap "swap")
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(def dup "dup")
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(def rot "rot")
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(def over "over")
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; Duplicate the top element of the stack
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(def _dup (fn (_) (
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(def _top (at 0 stack))
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(if (iserr _top) (prnl "dup: STACK EMPTY")
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(stkadd _top))
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)))
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; Swap the top two elements of the stack, if possible
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(def _swap (fn (_) (
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(if (> (len stack) 1) (
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(def (_b _a) ((bop 0) (bop 0)))
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(stkadd _b)
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(stkadd _a))
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(prnl "swap: STACK TOO SMALL")
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))))
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; Rotate the third element to be above the first and second elements
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(def _rot (fn (_) (
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(if (> (len stack) 2) (
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(def (_c _b _a) ((bop 0) (bop 0) (bop 0)))
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(stkadd _b)
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(stkadd _c)
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(stkadd _a))
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(prnl "rot: STACK TOO SMALL")
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))))
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; Rotate the third element to be above the first and second elements
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(def _over (fn (_) (
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(if (> (len stack) 1) (
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(def _a (at 1 stack))
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(stkadd _a))
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(prnl "over: STACK TOO SMALL")
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))))
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; Defines a given symbol using a given list of Forth inputs
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(def compile (fn (func sym) (
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(def _x (at 0 func))
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(if (= _x "$") (rest func)
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(at 1 (
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(defe sym (ap (eval sym) _x))
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(compile (rest func) sym))
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)))))
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; Evaluate a list of Forth inputs
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(def feval (fn (list) (
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(if (> (len list) 0) (
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(def _x (at 0 list))
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(if (isnum _x) (stkadd _x) ; Push to the stack if it's a number
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(if (= "." _x) (pop 0) ; Pop if it's a dot
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(if (= + _x) (twop +) ; Try basic arithmetic
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(if (= - _x) (twop -)
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(if (= * _x) (twop *)
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(if (= / _x) (twop /)
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(if (= "swap" _x) (_swap 0)
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(if (= "dup" _x) (_dup 0)
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(if (= "rot" _x) (_rot 0)
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(if (= "over" _x) (_over 0)
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(if (= "^" _x) (pch (bop 0))
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(if (= ":" _x) ( ; Compile a phrase into the next symbol
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(def var (at 1 list)) ; Collect the symbol to define, as a string
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(defe var (+ "_" var)) ; Add an underscore for the internal storage
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(defe (+ "_" var) ()) ; Define internally as an empty list
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(def list (compile ; Overwrite list with output of (compile)
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(rest (rest list)) ; Current list, not including ':' or the symbol
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(+ "_" var)))) ; The internal variable name
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( ; If none of the above hit, try to interpret as a compiled symbol
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(def _e (eval _x))
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(if (iserr (len _e)) () (feval _e))
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)
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))))))))))))
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; A switch/case operator might be good, to avoid huge closing-paren chains
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; If any list is left, recurse into it
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(if (> (len list) 0) (feval (rest list)) ())
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) () ; Meow!
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))))
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; A simple test of the built-in arithmetic
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(def test (fn (_) (
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(prnl "Should match:")
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(prnl "18 33 4 -4")
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(feval ( 6 3 * . 32 ^ 100 3 / . 32 ^ 2 2 + . 32 ^ 5 9 - . ))
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(pch 10)
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(pch 10)
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)))
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;; Example Compilations
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; Basic imperial distances
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(feval (: "ft" 12 * $))
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(feval (: "yd" ft 3 * $))
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(feval (: "in" $))
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(feval (: "i>f" 1 ft / $))
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(feval (: "i>y" 1 yd / $))
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; Convert between Farenheit and Celcius
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(feval (: "f>c" 32 - 5 * 9 /$))
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(feval (: "c>f" 9 * 5 / 32 + $))
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; Math
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(feval (: "sq" dup * $))
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; Gets next Fibonacci number from two on stack
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(feval (: "fib" swap over + dup . $))
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; A simple REPL. Exits on 'q'
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(def repl (fn (_) (
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(prn "forbble::> ")
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(def _inp (inp 0 0))
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(if (= "q" _inp) () (
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(def _str (+ "(feval (" _inp "))" ))
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(eval _str)
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(pch 10)
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(repl 0)
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)))))
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; Run the REPL
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(repl 0)
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