50 lines
2.5 KiB
Plaintext
50 lines
2.5 KiB
Plaintext
; We don't have atoms built in, mutable vectors
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; are our base building block. In order to make the
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; following BF implementation nice, let's add atoms!
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; They will be implmented as length 1 vectors with nice syntax for deref
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(fun make-atom (x) [x])
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(fun set-atom! (x y) (set-idx! x 0 y))
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(fun get-atom (x) (idx x 0))
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(add_grammar_rule 'form ["@" 'form] (lambda (_ x) `(get-atom ~x)))
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; Now begin by defining our BF syntax & semantics
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; Define our tokens as BF atoms
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(add_grammar_rule 'bfs_atom ["<"] (lambda (_) '(set-atom! cursor (- @cursor 1))))
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(add_grammar_rule 'bfs_atom [">"] (lambda (_) '(set-atom! cursor (+ @cursor 1))))
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(add_grammar_rule 'bfs_atom ["\\+"] (lambda (_) '(set-idx! tape @cursor (+ (idx tape @cursor) 1))))
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(add_grammar_rule 'bfs_atom ["-"] (lambda (_) '(set-idx! tape @cursor (- (idx tape @cursor) 1))))
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(add_grammar_rule 'bfs_atom [","] (lambda (_) '(let (value (idx input @inptr))
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(do (set-atom! inptr (+ 1 @inptr))
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(set-idx! tape @cursor value)))))
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(add_grammar_rule 'bfs_atom ["."] (lambda (_) '(set-atom! output (concat [(idx tape @cursor)] @output))))
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; Define strings of BF atoms
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(add_grammar_rule 'bfs ['bfs_atom *] (lambda (x) x))
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; Add loop as an atom
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; (note that closure cannot yet close over itself by value, so we pass it in)
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(add_grammar_rule 'bfs_atom ["\\[" 'bfs "]"] (lambda (_ x _)
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`(let (f (lambda (f)
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(if (= 0 (idx tape @cursor))
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nil
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(do ,x (f f)))))
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(f f))))
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; For now, stick BFS rule inside an unambigious BFS block
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; Also add setup code
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(add_grammar_rule 'form ["bf" 'optional_WS "{" 'optional_WS 'bfs 'optional_WS "}"]
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(lambda (_ _ _ _ x _ _)
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`(lambda (input)
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(let (
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tape (vector 0 0 0 0 0)
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cursor (make-atom 0)
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inptr (make-atom 0)
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output (make-atom (vector))
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)
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(do (println "beginning bfs") ,x (idx output 0))))))
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; Let's try it out! This BF program prints the input 3 times
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(println (bf { ,>+++[<.>-] } [1337]))
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; we can also have it compile into our main program
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(fun main () (do (println "BF: " (bf { ,>+++[<.>-] } [1337])) 0))
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