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;;;; l-system.lisp
(in-package #:l-system)
;;; "l-system" goes here. Hacks and glory await!
(defparameter *l-system-clauses* (make-hash-table :test 'equal))
(defun l-system (fn axiom depth)
(iter (repeat depth)
(with result = axiom)
(setf result
(funcall fn result))
(finally (return result))))
(defun parametric-grammar (elements)
(iter (for (symbol . parameters) in elements)
(for func = (gethash symbol *l-system-clauses*))
(appending (if (functionp func)
(apply func parameters)
(list `(,symbol ,@parameters))))))
(defun context-sensitive-grammar (elements)
(iter (for elt on elements)
(with symbol0 = nil)
(for (symbol1 . parameters1) = (first elt))
(for symbol2 = (first (second elt)))
(for func = (or (gethash (list symbol0 symbol1 symbol2) *l-system-clauses*)
(gethash symbol1 *l-system-clauses*)))
(appending (if (functionp func)
(apply func parameters1)
(list `(,symbol1 ,@parameters1))))
(setf symbol0 (first (first elt)))))
(defmacro setf-l-system-rule (symbol lambda)
`(setf (gethash ,symbol *l-system-clauses*)
,lambda))
(defun make-l-system-expr (item)
`(list ',(first item) ,@(rest item)))
(defun make-l-system-list (rest)
(iter (for item in rest)
(collecting (make-l-system-expr item))))
(defmacro make-l-system-rule (vars &body body)
`#'(lambda ,(append vars '(&rest rest))
(declare (ignorable rest))
(list ,@(make-l-system-list body))))
(defmacro -> (symbol vars &body body)
`(setf-l-system-rule ',symbol
(make-l-system-rule ,vars ,@body)))
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