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[PATCH] Gnu Elpa: stream.el: Add some more basic stream operations
From: |
Michael Heerdegen |
Subject: |
[PATCH] Gnu Elpa: stream.el: Add some more basic stream operations |
Date: |
Thu, 02 Jun 2016 17:42:10 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.0.94 (gnu/linux) |
Hello,
here is a patch that adds some missing stream operations.
---
packages/stream/stream.el | 59 +++++++++++++++++++++++++++++++++++
packages/stream/tests/stream-tests.el | 32 +++++++++++++++++++
2 files changed, 91 insertions(+)
diff --git a/packages/stream/stream.el b/packages/stream/stream.el
index 22cecac..7728338 100644
--- a/packages/stream/stream.el
+++ b/packages/stream/stream.el
@@ -333,6 +333,65 @@ calling this function."
(cl-defmethod seq-copy ((stream stream))
"Return a shallow copy of STREAM."
(stream-delay stream))
+
+
+;;; More stream operations
+
+(defun stream-scan (function init stream)
+ "Return a stream of successive reduced values for STREAM.
+
+If the elements of a stream s are s_1, s_2, ..., the elements
+S_1, S_2, ... of the stream returned by \(stream-scan f init s\)
+are defined recursively by
+
+ S_1 = init
+ S_(n+1) = (funcall f S_n s_n)
+
+as long as s_n exists.
+
+Example:
+
+ (stream-scan #'* 1 (stream-range 1))
+
+returns a stream of the factorials."
+ (let ((res init))
+ (stream-cons
+ res
+ (seq-map (lambda (el) (setq res (funcall function res el)))
+ stream))))
+
+(defun stream-flush (stream)
+ "Request all elements from STREAM in order for side effects only."
+ (while (not (stream-empty-p stream))
+ (cl-callf stream-rest stream)))
+
+(defun stream-iterate-function (function value)
+ "Return a stream of repeated applications of FUNCTION to VALUE.
+The returned stream starts with VALUE. Any successive element
+will be found by calling FUNCTION on the preceding element."
+ (stream-cons
+ value
+ (stream-iterate-function function (funcall function value))))
+
+(defun stream-reduce (function init stream)
+ "Reduce two-argument FUNCTION across STREAM starting with INIT."
+ (let ((res init))
+ (stream-flush (seq-map (lambda (el) (setq res (funcall function res el)))
stream))
+ res))
+
+(defun stream-concatenate (stream-of-streams)
+ "Concatenate all streams in STREAM-OF-STREAMS and return the result.
+All elements in STREAM-OF-STREAMS must be streams. The result is
+a stream."
+ (stream-reduce #'stream-append (stream-empty) stream-of-streams))
+
+(defun stream-mapconcat (function stream separator)
+ "Apply FUNCTION to each element of STREAM and concat the results as strings.
+In between of each pair of results, stick in SEPARATOR. This is
+like `mapconcat', but for streams."
+ (if (stream-empty-p stream) ""
+ (let ((mapped (seq-map function stream)))
+ (stream-reduce (lambda (x y) (concat x separator y)) (stream-first
mapped) (stream-rest mapped)))))
(defun stream-of-directory-files-1 (directory &optional nosort recurse
follow-links)
"Helper for `stream-of-directory-files'."
diff --git a/packages/stream/tests/stream-tests.el
b/packages/stream/tests/stream-tests.el
index 23a54b5..360a405 100644
--- a/packages/stream/tests/stream-tests.el
+++ b/packages/stream/tests/stream-tests.el
@@ -242,5 +242,37 @@
(should (= 2 (stream-first str)))
(should (null (stream-pop stream-empty)))))
+(ert-deftest stream-scan-test ()
+ (should (eq (seq-elt (stream-scan #'* 1 (stream-range 1)) 4) 24)))
+
+(ert-deftest stream-flush-test ()
+ (should (let* ((times 0)
+ (count (lambda () (cl-incf times))))
+ (letrec ((make-test-stream (lambda () (stream-cons (progn (funcall
count) nil)
+ (funcall
make-test-stream)))))
+ (stream-flush (seq-take (funcall make-test-stream) 5))
+ (eq times 5)))))
+
+(ert-deftest stream-iterate-function-test ()
+ (should (equal (list 0 1 2) (seq-into-sequence (seq-take
(stream-iterate-function #'1+ 0) 3)))))
+
+(ert-deftest stream-reduce ()
+ (should (eq (stream-reduce #'* 1 (seq-take (stream-range 1) 4)) 24)))
+
+(ert-deftest stream-concatenate-test ()
+ (should (equal (seq-into-sequence
+ (stream-concatenate
+ (stream (list (stream (list 1 2 3))
+ (stream (list))
+ (stream (list 4))
+ (stream (list 5 6 7 8 9))))))
+ (list 1 2 3 4 5 6 7 8 9))))
+
+(ert-deftest stream-mapconcat-test ()
+ (should (equal (stream-mapconcat #'capitalize (stream (list))
",") ""))
+ (should (equal (stream-mapconcat #'capitalize (stream (list "a"))
",") "A"))
+ (should (equal (stream-mapconcat #'capitalize (stream (list "a" "b"))
",") "A,B"))
+ (should (equal (stream-mapconcat #'capitalize (stream (list "a" "b" "c"))
",") "A,B,C")))
+
(provide 'stream-tests)
;;; stream-tests.el ends here
--
2.8.1
Thanks,
Michael.
- [PATCH] Gnu Elpa: stream.el: Add some more basic stream operations,
Michael Heerdegen <=
- Re: [PATCH] Gnu Elpa: stream.el: Add some more basic stream operations, Michael Heerdegen, 2016/06/02
- Re: [PATCH] Gnu Elpa: stream.el: Add some more basic stream operations, Nicolas Petton, 2016/06/02
- Re: [PATCH] Gnu Elpa: stream.el: Add some more basic stream operations, Michael Heerdegen, 2016/06/02
- Re: [PATCH] Gnu Elpa: stream.el: Add some more basic stream operations, Michael Heerdegen, 2016/06/08
- Re: [PATCH] Gnu Elpa: stream.el: Add some more basic stream operations, Nicolas Petton, 2016/06/09
- Re: [PATCH] Gnu Elpa: stream.el: Add some more basic stream operations, Michael Heerdegen, 2016/06/09
- Re: [PATCH] Gnu Elpa: stream.el: Add some more basic stream operations, Nicolas Petton, 2016/06/09
- Re: [PATCH] Gnu Elpa: stream.el: Add some more basic stream operations, Davis Herring, 2016/06/09
- Re: [PATCH] Gnu Elpa: stream.el: Add some more basic stream operations, Michael Heerdegen, 2016/06/09
- Re: [PATCH] Gnu Elpa: stream.el: Add some more basic stream operations, Yuri Khan, 2016/06/09