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-rw-r--r--utilities.lisp16
1 files changed, 11 insertions, 5 deletions
diff --git a/utilities.lisp b/utilities.lisp
index 414f0f2..c231f72 100644
--- a/utilities.lisp
+++ b/utilities.lisp
@@ -19,7 +19,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|#
(defun extract-keys (alist)
- "Extract the keys of associative lists."
+ "Extract the keys of an associative list."
(let ((return-value nil))
(progn
(dolist (i alist)
@@ -27,8 +27,11 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
(cons (car i) return-value)))
(reverse return-value))))
+(defun last-char (s)
+ (char s (- (length s) 1)))
+
(defun hexd? (string)
- "Is a string a hexd number?"
+ "Is string a hexadecimal number?"
(let ((stack ()))
(dotimes (i (length string))
(push
@@ -45,9 +48,10 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
(eval stack)))
(defun hex2dec (string)
- "Convert an arbitrarily sized hexd number (as string) to a positive decimal."
+ "Convert an arbitrarily sized hexadecimal number (as string) to a positive decimal."
(if (hexd? string)
- (flet ((hex (c) ;Return character as hexadecimal
+ ;; Return a character as a hexadecimal digit.
+ (flet ((hex (c)
(cond
((and (char-not-lessp c #\0)
(char-not-greaterp c #\9))
@@ -58,6 +62,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
(+ (- (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) ())
@@ -66,4 +71,5 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
(* (expt 16 j)
(hex (char string i))))))
return-value))
- nil))
+ ;; Return nil if string was not a hexadecimal number.
+ nil))