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;; Copyright (C) 2007-2011, Gabriel Dos Reis.
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;;; The types "bit" and "bit vector" are implemented differently
;;; in different variants of lisp.
;;; These lisp macros/functions will have different implementations 
;;; on different lisp systems.

;;; The operations which traverse entire vectors are given as functions
;;; since the function calling overhead will be relatively small.
;;; The operations which extract or set a single part of the vector are
;;; provided as macros.

(IMPORT-MODULE "boot-pkg")
(in-package "BOOT")

;;; SMW Nov 88: Created
 
(defmacro truth-to-bit (x) `(cond (,x 1) ('else 0)))
(defmacro bit-to-truth (b) `(eql ,b 1))

(defun    bvec-make-full (n x) 
    (make-array (list n) :element-type 'bit :initial-element x))

(defmacro bvec-elt       (bv i)    `(sbit ,bv ,i))
(defmacro bvec-setelt    (bv i x)  `(setf (sbit ,bv ,i) ,x))

(defun    bvec-greater   (bv1 bv2)
  (let ((pos (mismatch bv1 bv2)))
    (cond ((or (null pos) (>= pos (length bv1))) nil)
          ((< pos (length bv2)) (> (bit bv1 pos) (bit bv2 pos)))
          ((find 1 bv1 :start pos) t)
          (t nil))))