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;; -*- mode: common-lisp -*-
#|
clasm-6502: An assembler for the 6502 written in Common Lisp.
Copyright (C) 2024 Aleksei Eaves
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|#
(defun extract-keys (alist)
"Extract the keys of an associative list."
(let ((return-value nil))
(progn
(dolist (i alist)
(setf return-value
(cons (car i) return-value)))
(reverse return-value))))
(defun last-char (s)
(char s (- (length s) 1)))
(defun hexd? (string)
"Is string a hexadecimal number?"
(let ((stack ()))
(dotimes (i (length string))
(push
(or (and (char-not-lessp
(char string i) #\0)
(char-not-greaterp
(char string i) #\9))
(and (char-not-lessp
(char string i) #\A)
(char-not-greaterp
(char string i) #\F)))
stack))
(push 'and stack)
(eval stack)))
(defun hex2dec (string)
"Convert an arbitrarily sized hexadecimal number (as string) to a positive decimal."
(if (hexd? string)
;; Return a character as a hexadecimal digit.
(flet ((hex (c)
(cond
((and (char-not-lessp c #\0)
(char-not-greaterp c #\9))
(- (char-code c)
(char-code #\0)))
((and (char-not-lessp c #\A)
(char-not-greaterp c #\F))
(+ (- (char-code (char-downcase c))
(char-code #\a)) 10)))))
(let ((return-value 0))
;; Loop through string and convert.
(do ((i 0 (incf i))
(j (- (length string) 1) (decf j)))
((minusp j) ())
(setf return-value
(+ return-value
(* (expt 16 j)
(hex (char string i))))))
return-value))
;; Return nil if string was not a hexadecimal number.
nil))
|
