From 4d6ded823b9680c08c27bfd5e50d94dc1209df1a Mon Sep 17 00:00:00 2001
From: Colin Okay <cbeok@protonmail.com>
Date: Wed, 8 Jul 2020 16:22:43 -0500
Subject: moved examples to their own package

---
 examples.lisp | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 gtwiwtg.lisp  | 51 +---------------------------------------------
 2 files changed, 66 insertions(+), 50 deletions(-)
 create mode 100644 examples.lisp

diff --git a/examples.lisp b/examples.lisp
new file mode 100644
index 0000000..2893447
--- /dev/null
+++ b/examples.lisp
@@ -0,0 +1,65 @@
+(defpackage #:gtwiwtg.examples
+  (:use #:cl #:gtwiwtg)
+  (:export #:perms #:all-primes))
+
+(in-package :gtwiwtg.examples)
+
+;; permutations
+
+
+(defun fill-and-insert (idx elem vec buffer)
+  "A utilty function that modifies BUFFER. 
+
+The length of BUFFER is one greater than the length of VEC. 
+
+This function fills the first IDX fields of BUFFER with the first IDX
+fields of VEC. Fills the field of BUFFER at IDX with ELEM.  Fills the
+remaining fields of BUFFER with the remaining fields of VEC.
+"
+  (loop :for i :below (length buffer)
+     :when (= i idx) :do (setf (aref buffer idx) elem)
+     :when (< i idx) :do (setf (aref buffer i)
+                               (aref vec i))
+     :when (> i idx) :do (setf (aref buffer i)
+                               (aref vec (1- i))))  )
+
+(defun thread-through (elem vec)
+  "Creates a generator that produces a series of N vectors of length
+N, where N is one greater than the length of VEC.  The vectors
+produced by this generator have the same elements of VEC but have ELEM
+inserted at each possible spot, N spots in all. 
+
+Note: The generator reuses the memory that it returns on each step. If
+you intend to collect to products of the generator, you should copy
+them to somehow first.
+"
+  (let ((buffer (concatenate 'vector vec (list elem)))) ;; reusable buffer
+    (map! (lambda (idx)
+            (fill-and-insert idx elem vec buffer)
+            buffer)
+          (range :from 0 :to (length vec) :inclusive t))))
+
+
+(defun perms (vec)
+  "Creates a generator that produces all of the permutations of the
+vector VEC, one at a time."
+  (if (= 1 (length vec)) (seq (list vec))
+      (let ((elem (elt vec 0))
+            (subperms (perms (make-array (1- (length vec))
+                                         :displaced-to vec
+                                         :displaced-index-offset 1
+                                         :element-type (array-element-type vec)))))
+        (inflate! (lambda (subperm) (thread-through elem subperm)) subperms))))
+
+;; primes
+
+(defun prime-p (n)
+  (loop
+     :for x :from 2 :upto (sqrt n)
+     :when (zerop (mod n x)) :do (return nil)
+     :finally (return t)))
+
+(defun all-primes ()
+  (filter! #'prime-p (range :from 1)))
+
+
diff --git a/gtwiwtg.lisp b/gtwiwtg.lisp
index fe0f679..5938065 100644
--- a/gtwiwtg.lisp
+++ b/gtwiwtg.lisp
@@ -592,7 +592,7 @@ Example: a usless calculation
         ((x y) (zip! (times 10) (range :by -1)))
         (sqrt (+ acc (* x y))))
 
-#C(0.4498776 9.987898)
+ #C(0.444279 8.986663)
 
 Example: building data 
 
@@ -684,52 +684,3 @@ is minimal among the values of GEN.  VALUE is the value of (FUNCALL FN X)"
               am))))
 
 
-;;; EXAMPLES
-
-
-;; permutations
-
-(defun fill-and-insert (idx elem vec buffer)
-  "A Utility function that inserts ELEM at IDX into BUFFER. For every
-other space in BUFFER, the lements of VEC are inserted in order.
-
-Implicity expects (= (LENGTH BUFFER) (1+ (LENGTH VEC)))
-
-Not meant for general use. just a utility used by THREAD-THROUGH"
-  (loop :for i :below (length buffer)
-     :when (= i idx) :do (setf (aref buffer idx) elem)
-     :when (< i idx) :do (setf (aref buffer i)
-                               (aref vec i))
-     :when (> i idx) :do (setf (aref buffer i)
-                               (aref vec (1- i))))  )
-
-(defun thread-through (elem vec)
-  (let ((buffer (concatenate 'vector vec (list elem)))) ;; reusable buffer
-    (map! (lambda (idx)
-            (fill-and-insert idx elem vec buffer)
-            buffer)
-          (range :from 0 :to (length vec)))))
-
-
-(defun perms (vec)
-  (if (= 1 (length vec)) (seq (list vec))
-      (let ((elem (elt vec 0))
-            (subperms (perms (make-array (1- (length vec))
-                                         :displaced-to vec
-                                         :displaced-index-offset 1
-                                         :element-type (array-element-type vec)))))
-        (inflate! (lambda (subperm) (thread-through elem subperm)) subperms))))
-
-
-;; primes
-
-(defun prime-p (n)
-  (loop
-     :for x :from 2 :upto (sqrt n)
-     :when (zerop (mod n x)) :do (return nil)
-     :finally (return t)))
-
-(defun all-primes ()
-  (filter! #'prime-p (range :from 1)))
-
-
-- 
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