From: duerst@...
Date: 2016-12-08T09:22:03+00:00
Subject: [ruby-core:78543] [Ruby trunk Feature#13016] String#gsub(hash)

Issue #13016 has been updated by Martin D��rst.


Shyouhei Urabe wrote:
> I noticed that I can't purge `NKF.nkf '-Z4'`.  It can neither be rewritten using String#tr, String#encode, nor String#unicode_normalize.

Can you give (a pointer to) a detailed description of what NKF, and in particular NKF.nkf -Z4, does exactly? For example, I can't find it at http://blog.layer8.sh/ja/2012/03/31/nkf_command_option/. The following may be related: ���-Z     X0208������������������������������������ASCII������������������-Z1���X0208��� ������ASCII space������������������-Z2���X0208���������ASCII space ������������������������������������������������������������������������(���������������X0208���������������������������������������������������������)

> It is doable using String#gsub theoretically, but that requires a hand-crafted nontrivial regular expression that exactly matches what Z4 expects to convert.  This is almost impossible to do, and is definitely not something debuggable.

Please note that String#unicode_normalize, as currently implemented, also uses some huge regular expressions (though program-generated). And also has (hopefully) successfully been debugged, although with the help of testing data from Unicode.



----------------------------------------
Feature #13016: String#gsub(hash)
https://bugs.ruby-lang.org/issues/13016#change-61928

* Author: Shyouhei Urabe
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------
Background: I wanted to drop NKF dependency of my script.  By doing so I noticed that I can't purge `NKF.nkf '-Z4'`.  It can neither be rewritten using String#tr, String#encode, nor String#unicode_normalize. It is doable using String#gsub theoretically, but that requires a hand-crafted nontrivial regular expression that exactly matches what Z4 expects to convert.  This is almost impossible to do, and is definitely not something debuggable.

Proposal: extend String#gsub so that it also accepts hash as its only argument, specifying input-output mapping.

```ruby
# now
def convert str
  require 'nkf'
  NKF.nkf '-Z4xm0', str
end

# proposed
def convert str
  map = {  "\u3002" => "\uFF61", "\u300C" => "\uFF62", ... }
  str.gsub map
end
```



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