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Feature #6445

request for default length/position on string index

Added by botp (bot pena) about 6 years ago. Updated 5 months ago.

Status:
Assigned
Priority:
Normal
Target version:
-
[ruby-core:45106]

Description

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]

History

#1 [ruby-core:45167] Updated by mame (Yusuke Endoh) about 6 years ago

  • 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 mame@tsg.ne.jp

#2 [ruby-core:45357] Updated by knu (Akinori MUSHA) almost 6 years ago

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?

#3 [ruby-core:48247] Updated by yhara (Yutaka HARA) over 5 years ago

  • Target version changed from 2.0.0 to Next Major

#4 [ruby-core:48249] Updated by yhara (Yutaka HARA) over 5 years ago

  • Target version changed from Next Major to 2.6

#5 Updated by naruse (Yui NARUSE) 5 months ago

  • Target version deleted (2.6)

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