patch 8.2.2065: using map() and filter() on a range() is inefficient
Problem: Using map() and filter() on a range() is inefficient.
Solution: Do not materialize the range. (closes #7388)
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index fb0b193..d6e408a 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -2302,6 +2302,7 @@
" filter()
call assert_equal([1, 3], filter(range(5), 'v:val % 2'))
+ call assert_equal([1, 5, 7, 11, 13], filter(filter(range(15), 'v:val % 2'), 'v:val % 3'))
" funcref()
call assert_equal([0, 1], funcref('TwoArgs', range(2))())
@@ -2358,6 +2359,9 @@
" map()
call assert_equal([0, 2, 4, 6, 8], map(range(5), 'v:val * 2'))
+ call assert_equal([3, 5, 7, 9, 11], map(map(range(5), 'v:val * 2'), 'v:val + 3'))
+ call assert_equal([2, 6], map(filter(range(5), 'v:val % 2'), 'v:val * 2'))
+ call assert_equal([2, 4, 8], filter(map(range(5), 'v:val * 2'), 'v:val % 3'))
" match()
call assert_equal(3, match(range(5), 3))