Feature #3845
Updated by matz (Yukihiro Matsumoto) over 12 years ago
=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