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authorJeremy Evans <code@jeremyevans.net>2019-08-08 20:09:17 (GMT)
committerJeremy Evans <code@jeremyevans.net>2019-09-02 05:20:05 (GMT)
commit83498854eb5a824f1f83c31fac18c9279f9ee10d (patch)
tree86687179ce82e43662c154235b25f8dcaa889565
parent79e3d6bb9e007fc97153c1097daf78e9a201a642 (diff)
Make Enumerator::Lazy#with_index be lazy
Previously, Enumerator::Lazy#with_index was not defined, so it picked up the default implementation from Enumerator, which was not lazy. Based on earlier patch from nobu. Fixes [Bug #7877]
-rw-r--r--enumerator.c66
-rw-r--r--test/ruby/test_lazy_enumerator.rb22
2 files changed, 88 insertions, 0 deletions
diff --git a/enumerator.c b/enumerator.c
index 96daad2..d4022ae 100644
--- a/enumerator.c
+++ b/enumerator.c
@@ -3597,6 +3597,71 @@ arith_seq_size(VALUE self)
return len;
}
+static VALUE
+lazy_with_index_func(RB_BLOCK_CALL_FUNC_ARGLIST(val, offset))
+{
+ VALUE yielder, memo, result;
+ VALUE e = rb_enum_values_pack(argc - 1, argv + 1);
+ long idx;
+
+ yielder = argv[0];
+ memo = rb_attr_get(yielder, id_memo);
+ if (NIL_P(memo))
+ memo = offset;
+ idx = NUM2LONG(memo);
+ result = rb_assoc_new(e, memo);
+ rb_funcall(yielder, idLTLT, 1, result);
+ rb_ivar_set(yielder, id_memo, LONG2NUM(++idx));
+ return Qnil;
+}
+
+static VALUE
+lazy_with_index_iter(RB_BLOCK_CALL_FUNC_ARGLIST(val, offset))
+{
+ VALUE yielder, memo, result;
+ VALUE e = rb_enum_values_pack(argc - 1, argv + 1);
+ long idx;
+
+ yielder = argv[0];
+ memo = rb_attr_get(yielder, id_memo);
+ if (NIL_P(memo))
+ memo = offset;
+ idx = NUM2LONG(memo);
+ result = rb_yield(rb_assoc_new(e, memo));
+ rb_funcall(yielder, idLTLT, 1, result);
+ rb_ivar_set(yielder, id_memo, LONG2NUM(++idx));
+ return Qnil;
+}
+
+/*
+ * call-seq:
+ * lazy.with_index(offset = 0) {|(*args), idx| ... }
+ * lazy.with_index(offset = 0)
+ *
+ * Iterates the given block for each element with an index, which
+ * starts from +offset+. If no block is given, returns a new
+ * lazy enumerator that includes the index, starting from +offset+
+ *
+ * +offset+:: the starting index to use
+ *
+ * see Enumerator#with_index.
+ */
+static VALUE
+lazy_with_index(int argc, VALUE *argv, VALUE obj)
+{
+ VALUE memo;
+
+ rb_scan_args(argc, argv, "01", &memo);
+ if (NIL_P(memo))
+ memo = LONG2NUM(0);
+
+ return lazy_set_method(rb_block_call(rb_cLazy, id_new, 1, &obj,
+ rb_block_given_p() ?
+ lazy_with_index_iter : lazy_with_index_func,
+ memo),
+ rb_ary_new_from_values(argc, argv), 0);
+}
+
void
InitVM_Enumerator(void)
{
@@ -3654,6 +3719,7 @@ InitVM_Enumerator(void)
rb_define_method(rb_cLazy, "slice_when", lazy_super, -1);
rb_define_method(rb_cLazy, "chunk_while", lazy_super, -1);
rb_define_method(rb_cLazy, "uniq", lazy_uniq, 0);
+ rb_define_method(rb_cLazy, "with_index", lazy_with_index, -1);
#if 0 /* for RDoc */
rb_define_method(rb_cLazy, "to_a", lazy_to_a, 0);
diff --git a/test/ruby/test_lazy_enumerator.rb b/test/ruby/test_lazy_enumerator.rb
index e76a53e..80977a0 100644
--- a/test/ruby/test_lazy_enumerator.rb
+++ b/test/ruby/test_lazy_enumerator.rb
@@ -587,4 +587,26 @@ EOS
assert_equal([4, 6, 6, 4, 0, 4], e.first(6))
assert_equal([4, 6, 6, 4, 0, 4], e.first(6))
end
+
+ def test_with_index
+ feature7877 = '[ruby-dev:47025] [Feature #7877]'
+ leibniz = ->(n) {
+ (0..Float::INFINITY).lazy.with_index {|i, j|
+ raise IndexError, "limit exceeded (#{n})" unless j < n
+ ((-1) ** j) / (2*i+1).to_f
+ }.take(n).reduce(:+)
+ }
+ assert_nothing_raised(IndexError, feature7877) {
+ assert_in_epsilon(Math::PI/4, leibniz[1000])
+ }
+
+ ary = (0..Float::INFINITY).lazy.with_index(2) {|i, j| [i-1, j] }.take(2).to_a
+ assert_equal([[-1, 2], [0, 3]], ary)
+
+ ary = (0..Float::INFINITY).lazy.with_index(2).take(2).to_a
+ assert_equal([[0, 2], [1, 3]], ary)
+
+ ary = (0..Float::INFINITY).lazy.with_index.take(2).to_a
+ assert_equal([[0, 0], [1, 1]], ary)
+ end
end