Feature #11782
closed
String#+@ and String#-@
Description
Matz said
In fact, my best choice is introducing
String#+that returns a mutable copy of a string.
[ruby-core:71879] [Ruby trunk - Bug #11759]
So that this is a ticket for that.
I'll commit it ASAP to check this methods before 2.3.
Specification:
-
+'foo'returns modifiable string. -
-'foo'returns frozen string (because wasters will freeze below 0 degree in Celsius).
Updated by matz (Yukihiro Matsumoto) almost 10 years ago
It's OK if we don't have strong objection.
Matz.
Updated by mame (Yusuke Endoh) almost 10 years ago
+1
--
Yusuke Endoh mame@ruby-lang.org
Updated by ko1 (Koichi Sasada) almost 10 years ago
- Status changed from Open to Closed
Applied in changeset r52917.
- string.c: introduce String#+@ and String#-@ to control
String mutability.
[Feature #11782]
Updated by ko1 (Koichi Sasada) almost 10 years ago
- Status changed from Closed to Assigned
Endo-san pointed out that +foo.upcase! is evaluated as +(foo.upcase!).
It can be problem. But any practical examples?
Mutate operations such as str = +'foo' << bar << baz works (because +@ is stronger than <<).
Evaluation with current implementation (no optimization)
require 'benchmark' N = 10_000_000 Benchmark.bm{|x| x.report{ N.times{ 'foo'.dup } } x.report{ N.times{ +'foo' } } x.report{ N.times{ 'foo'.freeze } } x.report{ N.times{ -'foo' } } } __END__ # frozen-string-literal: true user system total real 5.850000 0.010000 5.860000 ( 5.858450) 0.780000 0.000000 0.780000 ( 0.780911) 0.340000 0.000000 0.340000 ( 0.351072) 0.530000 0.000000 0.530000 ( 0.529234) # frozen-string-literal: false user system total real 2.540000 0.000000 2.540000 ( 2.533344) 0.750000 0.000000 0.750000 ( 0.752019) 0.350000 0.000000 0.350000 ( 0.349776) 1.180000 0.000000 1.180000 ( 1.180882) Updated by ko1 (Koichi Sasada) almost 10 years ago
The purpose of this proposal is to encourage frozen string literals and provide better way than "foo".dup. So that String#-@ can be redundancy.
Updated by ko1 (Koichi Sasada) almost 10 years ago
Quoted from DevelopersMeeting20151021Japan log:
https://bugs.ruby-lang.org/projects/ruby/wiki/DevelopersMeeting20151021Japan https://docs.google.com/document/d/1axnQv1A2SdRExw--_RzXXJAPrRyvN7MCIB0WrKcZaSE/pub
matz: i have another idea +“...” -> mutable, -”...” -> immutable. it is more clean than “...”.freeze. how about that, instead of the magic comment? i don’t care about pull-requests, but care about the representation of source code.
akr: …
matz: I don’t like magic comment, so that I hesitate to introduce it.
a_matsuda: + and - seems string operation. << -”foo” can be seen as a here document.
matz: I understand. + and - is not good idea.
matz: another idea: make ‘’’foo’’’ frozen. incompatibility is negligible.
matz: yet another idea: make single quoted strings frozen. This is incompatible.
Matz said "+ and - is not good idea.".
So that please check it.
Updated by rosenfeld (Rodrigo Rosenfeld Rosas) almost 10 years ago
how about splitting strings like this?
long_string = 'first part ' + 'second part ' + 'last part' Should long_string be optimized by the compiler to generate 'first part second part last part' as a frozen string, or should it actually perform the additions and generate a modified string?
Updated by bughit (bug hit) almost 10 years ago
What is primary use case for -'string'? I initially though it was to be a shorthand for 'string'.freeze, avoiding allocation (due to special compiler support), producing an interned frozen string. But it does a dup, so does -'string' lack compiler support, thus first allocating a normal string then duping and freezing a copy which is not interned? So instead of 0 allocations ('string'.freeze) you get 2 (-'string')?
Updated by jeremyevans0 (Jeremy Evans) about 4 years ago
- Status changed from Assigned to Closed