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Issue #3845 has been updated by matz (Yukihiro Matsumoto).
Description updated
Status changed from Assigned to Rejected
This proposal is only for cosmetics.
I don't want a new operator that does not introduce something new.
Matz.
----------------------------------------
Feature #3845: "in" infix operator
https://bugs.ruby-lang.org/issues/3845#change-25800
Author: mame (Yusuke Endoh)
Status: Rejected
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category:
Target version:
=begin
Hi,
I'd propose "in" infix operator.
(<arg> in <args>) yields true when <arg> is included in <arg>.
Otherwise it yields false.
p "found" if 1 in 1, 2, 3 #=> found
p "not found" if 0 in 1, 2, 3 #=> not found
"in" operator is clearer to the reader than Array#include?:
p "found" if [1, 2, 3].include?(1)
p "not found" if [1, 2, 3].include?(0)
This proposal is similar to Object#in? proposed in [ruby-core:23543].
But there are two differences:
- "in" operator does not pollute name space of Object class
- each candidate of "in" is evaluated lazily; for example,
1 in 1, 2, foo()
does not call the method "foo" because 1 is found before that.
Note that this proposal ensures the syntax compatibility, since
"in" is already a keyword for "for" statement. But "for" statement
is rarely used. This proposal utilizes the rarely-used keyword.
I wrote an experimental patch. It implements the operator as a
syntactic sugar to "case" statement:
<arg> in <args>
=> (case <arg>; when <args>; true; else false; end)
The patch causes no parser conflict.
One more thing. The following expression is rejected:
foo(x in 1, 2, 3)
This is because it is ambiguous; this expression can be interpreted
as three ways:
foo((x in 1), 2, 3)
foo((x in 1, 2), 3)
foo((x in 1, 2, 3))
You need write parentheses explicitly.
What do you think?
diff --git a/parse.y b/parse.y
index e085088..64318bd 100644
--- a/parse.y
+++ b/parse.y
@@ -745,6 +745,7 @@ static void token_info_pop(struct parser_params*, const char *token);
%nonassoc modifier_if modifier_unless modifier_while modifier_until
%left keyword_or keyword_and
%right keyword_not
+%nonassoc keyword_in
%nonassoc keyword_defined
%right '=' tOP_ASGN
%left modifier_rescue
@@ -1258,6 +1259,14 @@ expr : command_call
$$ = dispatch2(unary, ripper_id2sym('!'), $2);
%*/
}
+ | expr keyword_in args
+ {
+ /*%%%*/
+ $$ = NEW_CASE($1, NEW_WHEN($3, NEW_TRUE(), NEW_FALSE()));
+ /*%
+ $$ = dispatch2(in, $1, $3);
+ %*/
+ }
| arg
;
diff --git a/test/ripper/test_parser_events.rb b/test/ripper/test_parser_events.rb
index 5d76941..6005457 100644
--- a/test/ripper/test_parser_events.rb
+++ b/test/ripper/test_parser_events.rb
@@ -1107,4 +1107,8 @@ class TestRipper::ParserEvents < Test::Unit::TestCase
parse('/', :compile_error) {|msg| compile_error = msg}
assert_equal("unterminated regexp meets end of file", compile_error)
end
+
+ def test_in
+ assert_equal("[in(1,[1,2,3])]", parse('1 in 1, 2, 3'))
+ end
end if ripper_test
--
Yusuke Endoh <mame / tsg.ne.jp>
=end
--
http://bugs.ruby-lang.org/