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enum.c: Enumerable#tally

* enum.c (enum_tally): new methods Enumerable#tally, which group
  and count elements of the collection.  [Feature #11076]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67020 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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nobu committed Feb 7, 2019
1 parent e0f1b51 commit 673dc51c251588be3c9f4b5b5486cd80d46dfeee
Showing with 54 additions and 0 deletions.
  1. +6 −0 NEWS
  2. +43 −0 enum.c
  3. +5 −0 test/ruby/test_enum.rb
6 NEWS
@@ -24,6 +24,12 @@ sufficient information, see the ChangeLog file or Redmine

=== Core classes updates (outstanding ones only)

Enumerable::

New method::

* Added Enumerable#tally. [Feature #11076]

=== Stdlib updates (outstanding ones only)

CSV::
43 enum.c
@@ -935,6 +935,48 @@ enum_group_by(VALUE obj)
return enum_hashify(obj, 0, 0, group_by_i);
}

static void
tally_up(VALUE hash, VALUE group)
{
VALUE tally = rb_hash_aref(hash, group);
if (NIL_P(tally)) {
tally = INT2FIX(1);
}
else if (FIXNUM_P(tally) && tally < INT2FIX(FIXNUM_MAX)) {
tally += INT2FIX(1) & ~FIXNUM_FLAG;
}
else {
tally = rb_big_plus(tally, INT2FIX(1));
}
rb_hash_aset(hash, group, tally);
}

static VALUE
tally_i(RB_BLOCK_CALL_FUNC_ARGLIST(i, hash))
{
ENUM_WANT_SVALUE();
tally_up(hash, i);
return Qnil;
}

/*
* call-seq:
* enum.tally -> a_hash
*
* Tallys the collection. Returns a hash where the keys are the
* elements and the values are numbers of elements in the collection
* that correspond to the key.
*
* (1..6).tally { |i| i%3 } #=> {0=>2, 1=>2, 2=>2}

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@vipulnsward

vipulnsward Mar 3, 2019

@nobu I was curious to use this, but I see that this is actually not what it returns:

On ruby master:

irb(main):006:0> (1..6).tally { |i| i%3 }
=> {1=>1, 2=>1, 3=>1, 4=>1, 5=>1, 6=>1}

I assume this is still experimental?

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@nobu

nobu Mar 4, 2019

Author Member

The example was wrong.
See 5133bfa

*
*/

static VALUE
enum_tally(VALUE obj)
{
return enum_hashify(obj, 0, 0, tally_i);
}

static VALUE
first_i(RB_BLOCK_CALL_FUNC_ARGLIST(i, params))
{
@@ -4070,6 +4112,7 @@ Init_Enumerable(void)
rb_define_method(rb_mEnumerable, "reduce", enum_inject, -1);
rb_define_method(rb_mEnumerable, "partition", enum_partition, 0);
rb_define_method(rb_mEnumerable, "group_by", enum_group_by, 0);
rb_define_method(rb_mEnumerable, "tally", enum_tally, 0);
rb_define_method(rb_mEnumerable, "first", enum_first, -1);
rb_define_method(rb_mEnumerable, "all?", enum_all, -1);
rb_define_method(rb_mEnumerable, "any?", enum_any, -1);
@@ -294,6 +294,11 @@ def test_group_by
assert_equal(h, @obj.each_with_index.group_by(&cond))
end

def test_tally
h = {1 => 2, 2 => 2, 3 => 1}
assert_equal(h, @obj.tally)
end

def test_first
assert_equal(1, @obj.first)
assert_equal([1, 2, 3], @obj.first(3))

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