Feature #6445: request for default length/position on string index

• Status: Assigned
• Priority: Normal
• Assignee: matz (Yukihiro Matsumoto)
• Target version: -

[botp (bot pena)]

would be nice if ruby has default for "rest or up to end of string"

eg

"hello"[2,] => should default to "hello"[2..-1]
or
"hello"[2..] => should default to "hello"[2..-1]

[mame (Yusuke Endoh)]

• Status changed from Open to Assigned
• Assignee set to matz (Yukihiro Matsumoto)

Hello,

I created a patch that add a syntactic sugar from (arg..) to (arg..-1).

ary = [1, 2, 3, 4]
p ary[2..] #=> [3, 4]

Matz, what do you think?

diff --git a/parse.y b/parse.y
index 9f9093b..d272492 100644
--- a/parse.y
+++ b/parse.y
@@ -2168,6 +2168,18 @@ arg : lhs '=' arg
$$ = dispatch2(dot3, $1, $3);
%*/
}

• | arg tDOT2
• {
• /%%%/
• value_expr($1);
• $$ = NEW_DOT2($1, NEW_LIT(INT2FIX(-1)));
• if (nd_type($1) == NODE_LIT && FIXNUM_P($1->nd_lit)) {
• deferred_nodes = list_append(deferred_nodes, $$);
• }
• /*%
• $$ = dispatch2(dot2, $1, INT2FIX(-1));
• %*/
• } | arg '+' arg { /%%%/

--
Yusuke Endoh [e-mail]

[knu (Akinori MUSHA)]

It would look nice and work fine with indexing strings and arrays, but if it were put in you would've come to want (1..).each {|i| .. } to work as well.

It might be better to default the omitted end to +Infinity and then make {Array,String,..}#[] understand +Infinity as an index, I guess?

[yhara (Yutaka HARA)]

• Target version changed from 2.0.0 to 3.0

[yhara (Yutaka HARA)]

• Target version changed from 3.0 to 2.6

[naruse (Yui NARUSE)]

• Target version deleted (2.6)