Execute Brain****/Common Lisp: Difference between revisions

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(defun adjust-memory (state)

"Modifies memory and memory-pointer such that memory-pointer is a valid index to the memory array.

If it is too large, the array is extended; if it is negative, the array is extended, its contents are shifted forward and the memory-pointer is incremented, by an amount to make the memory ."

(cond ((>= (bf-state-memory-pointer state)

(~~array-dimension~~ (bf-state-memory state) 0))

(length (bf-state-memory state)))

(adjust-array (bf-state-memory state)

(1+ (bf-state-memory-pointer state))

:initial-element 0))

((< (bf-state-memory-pointer state) 0)

((minusp (bf-state-memory-pointer state))

(let ((extent (- (bf-state-memory-pointer state))))

(incf (bf-state-memory-pointer state) extent)

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(defun matching-bracket-for (program bracket-index)

(~~let~~ ((depth 0))

(loop with depth := 0

~~(loop~~ for index := bracket-index then (1+ index)

for index := bracket-index then (1+ index)

when (>= index (length program))

do (error ~~'fail~~)

do (error "unmatched bracket")

when (char= #\[ (elt program index))

do (incf depth)

when (char= #\] (elt program index))

do (decf depth)

until (= depth 0)

until (zerop depth)

finally (return index))))

finally (return index)))

(defun brainfuck-eval (state &optional (stream *standard-output*))

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(loop do (fresh-line)

(princ "BRAINFUCK> ")

(~~brainfuck-eval (make-~~bf~~-state :program~~ (read-line)))))

(bf (read-line))))

</lang>