From 368abdee7869e99fa287ec2e6b099ee4584372e5 Mon Sep 17 00:00:00 2001
From: "Adam R. Nelson" <adam@nels.onl>
Date: Thu, 11 Mar 2021 22:42:57 -0500
Subject: last-minute updates: clarify some documentation, add
 flexvector->generator

---
 implementation/flexvectors-body2.scm | 10 ++++++++++
 implementation/flexvectors.sld       |  2 +-
 implementation/tests.scm             | 18 ++++++++++++++++++
 3 files changed, 29 insertions(+), 1 deletion(-)

(limited to 'implementation')

diff --git a/implementation/flexvectors-body2.scm b/implementation/flexvectors-body2.scm
index ba3e2f5..6f37efe 100644
--- a/implementation/flexvectors-body2.scm
+++ b/implementation/flexvectors-body2.scm
@@ -389,3 +389,13 @@
 (define (generator->flexvector g)
   (assume (procedure? g))
   (flexvector-unfold eof-object? (lambda (x) x) (lambda (_) (g)) (g)))
+
+(define (flexvector->generator fv)
+  (assume (flexvector? fv))
+  (let ((i 0))
+    (lambda ()
+      (if (< i (flexvector-length fv))
+        (let ((element (flexvector-ref fv i)))
+          (set! i (+ i 1))
+          element)
+        (eof-object)))))
diff --git a/implementation/flexvectors.sld b/implementation/flexvectors.sld
index 25e1543..4bc7da3 100644
--- a/implementation/flexvectors.sld
+++ b/implementation/flexvectors.sld
@@ -38,7 +38,7 @@
           flexvector->vector flexvector->list flexvector->string
           vector->flexvector list->flexvector string->flexvector
           reverse-flexvector->list reverse-list->flexvector
-          generator->flexvector)
+          generator->flexvector flexvector->generator)
 
   (import (scheme base)
           (scheme case-lambda)
diff --git a/implementation/tests.scm b/implementation/tests.scm
index 329a8d6..e41f19c 100644
--- a/implementation/tests.scm
+++ b/implementation/tests.scm
@@ -64,6 +64,24 @@
   (flexvector->vector (string->flexvector "abc")))
 (test-equal "flexvector->string" "abc" (flexvector->string (flexvector #\a #\b #\c)))
 
+(define genlist '(a b c))
+(define (mock-generator)
+  (if (pair? genlist)
+    (let ((value (car genlist)))
+      (set! genlist (cdr genlist))
+      value)
+    (eof-object)))
+
+(test-equal "generator->flexvector" #(a b c)
+  (flexvector->vector (generator->flexvector mock-generator)))
+(test-equal "flexvector->generator" '(a b c #t)
+  (let* ((gen (flexvector->generator (flexvector 'a 'b 'c)))
+         (one (gen))
+         (two (gen))
+         (three (gen))
+         (four (eof-object? (gen))))
+    (list one two three four)))
+
 ; Nondestructive operations on one vector
 (let ((fv (flexvector 10 20 30)))
   (test-equal "flexvector->vector" #(10 20 30) (flexvector->vector fv))
-- 
cgit 1.4.1