Introduce lib.functions which includes helper functions

Splitting macros and functions into different packages and source code
makes it easier to look at.   Functions currently implemented:
- range: like Python's range
- parse-integer*: parse-integer but junk-allowed is set to t.

lib.functions.lisp

@@ -0,0 +1,31 @@
+;;; lib.functions.lisp - 2025-02-09
+
+;; Copyright (C) 2025 Aryadev Chavali
+
+;; This program 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 General Public License Version 2 for
+;; details.
+
+;; You may distribute and modify this code under the terms of the GNU General
+;; Public License Version 2, which you should have received a copy of along with
+;; this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Helpful functions for usage throughout the project.
+
+;;; Code:
+
+(in-package :lib.functions)
+
+(fn range (start end &optional (step 1)) (-> (fixnum fixnum &optional fixnum) list)
+  "Make a list of numbers from START to END (exclusive).  If STEP is given, then
+each member is STEP distance apart."
+  (if (<= end start)
+      (error (format nil "~a < ~a" end start))
+      (loop :for i :from start :to (1- end) :by step
+            :collect i)))
+
+(fn parse-integer* (inp) (-> (string) (or integer list))
+  (parse-integer inp :junk-allowed t))