[elpa] externals/stream bd614d022b 2/7: Add more efficient method for making streams from arrays.

[Stefan Monnier]

branch: externals/stream
commit bd614d022b043397e7294a5083e4dcf3f805e089
Author: Earl Hyatt <okamsn@protonmail.com>
Commit: Stefan Monnier <monnier@iro.umontreal.ca>

    Add more efficient method for making streams from arrays.
    
    * stream.el (stream): Add method for arrays that avoids creating 
sub-sequences.
    
    * tests/stream-tests.el (stream-array-test): Add test for new method.
---
 stream.el             | 18 ++++++++++++++++++
 tests/stream-tests.el |  4 ++++
 2 files changed, 22 insertions(+)

diff --git a/stream.el b/stream.el
index 2439f958cb..300f3b8ae2 100644
--- a/stream.el
+++ b/stream.el
@@ -173,6 +173,24 @@ SEQ can be a list, vector or string."
      (seq-elt seq 0)
      (stream (seq-subseq seq 1)))))
 
+(cl-defmethod stream ((array array))
+  "Return a stream built from the array ARRAY."
+  (let ((len (length array)))
+    (if (= len 0)
+        (stream-empty)
+      ;; This approach could avoid one level of indirection by setting
+      ;; `stream--updater' directly, but using `funcall' makes for a
+      ;; good example of how to use a custom updater function using the public
+      ;; interface.
+      (let ((idx 0))
+        (cl-labels ((updater ()
+                      (if (< idx len)
+                          (prog1 (cons (aref array idx)
+                                       (stream-make (funcall #'updater)))
+                            (setq idx (1+ idx)))
+                        nil)))
+          (stream-make (funcall #'updater)))))))
+
 (cl-defmethod stream ((list list))
   "Return a stream built from the list LIST."
   (if (null list)
diff --git a/tests/stream-tests.el b/tests/stream-tests.el
index ba304f1ee4..997dd8607b 100644
--- a/tests/stream-tests.el
+++ b/tests/stream-tests.el
@@ -234,6 +234,10 @@
   (dolist (list '(nil '(1 2 3) '(a . b)))
     (should (equal list (seq-into (stream list) 'list)))))
 
+(ert-deftest stream-array-test ()
+  (dolist (arr (list "cat" [0 1 2]))
+    (should (equal arr (seq-into (stream arr) (type-of arr))))))
+
 (ert-deftest stream-seq-subseq-test ()
   (should (stream-empty-p (seq-subseq (stream-range 2 10) 0 0)))
   (should (= (stream-first (seq-subseq (stream-range 2 10) 0 3)) 2))