From: Mark Hubbart <discord@...>
Date: 2004-09-09T18:35:35+09:00
Subject: Re: Q: Should String.upcase! work on a segment of a string?


On Sep 8, 2004, at 5:35 PM, Mike Hall wrote:

> Question: Should String.upcase! work on a segment of a string?
>
> We can assign to a sub-string, so I thought that a bang-method might 
> also work on a sub-string.
>
>   s = 'AA11zz'		# define a string
>
>> s[4..5].upcase!	# try to change part of it
>   => "ZZ"                       # yeah, ok, the new string is changed, 
> but...
>
>> s
>   => "AA11zz"		# the original string wasn't affected
>
>> s[4..5] = s[4..5].upcase    # so, do it by-hand
>   => "ZZ"
>
>> s				# and it's ok
>   => "AA11ZZ"
>
> Are there edge cases where this wouldn't be appropriate?

A string and it's substrings (as accessed by [] and slice) are not 
related. When you create a substring by taking a slice, it returns a 
copy of that section of data.

Still, this was one of the conveniences I missed from PHP. Here's an 
idea I've played around with a few times (dirty hack follows):

class SubString
   def initialize(string, range)
     @string, @range = string, range
   end
   def upcase!
     @string[@range] = @string[@range].upcase
   end
   # [...]
end

class String
   def sub_str(range)
     SubString.new(self, range)
   end
end

foo.sub_str(2..4).upcase!
     ==>"STI"
foo
     ==>"teSTIng foo testing"

foo.sub_str(/foo/).upcase!
     ==>"FOO"
foo
     ==>"teSTIng FOO testing"

cheers,
Mark