From: ts <decoux@...>
Date: 2001-09-04T17:04:15+09:00
Subject: [ruby-talk:20843] Re: modify hash during iteration

>>>>> "T" == Tomas Brixi <brixi@unicode.cz> writes:

T> The question was about modifying the value of the  key (pair[0])

 Don't modify the key otherwise you'll have result difficult to
 predict. Here a small example

pigeon% cat b.rb
#!/usr/bin/ruby
h = {}
('a' .. 'i').each {|k| h[k] = k}
h.each do |k, v|
   p "key : #{k}"
   h["a" + k] = v
end
p h
h = {}
('a' .. 'z').each {|k| h[k] = k}
h.each do |k, v|
   h["a" + k] = v
end
pigeon% 
pigeon% b.rb
"key : e"
"key : f"
"key : g"
"key : h"
"key : i"
"key : a"
"key : b"
"key : ae"
"key : c"
"key : af"
"key : d"
{"ag"=>"g", "e"=>"e", "ah"=>"h", "f"=>"f", "aa"=>"a", "ai"=>"i", "g"=>"g",
"ab"=>"b", "h"=>"h", "ac"=>"c", "i"=>"i", "a"=>"a", "ad"=>"d", "b"=>"b",
"aae"=>"e", "ae"=>"e", "c"=>"c", "aaf"=>"f", "af"=>"f", "d"=>"d"} 
./b.rb:12:in `each': rehash occurred during iteration (IndexError)
        from ./b.rb:11
pigeon% 


Guy Decoux