From: Dave Thomas <Dave@...>
Date: 2001-03-07T05:59:40+09:00
Subject: [ruby-talk:12179] Re: (long) Re: hash.invert loses data if equal values exist - is this the right behaviour?

gotoken@math.sci.hokudai.ac.jp (GOTO Kentaro) writes:

> >Of course this breaks down at "shi" => "four", "yon" => "four", but
> >there are many true one-to-one mappings where .invert can be useful.
> 
> Yes, it could be useful sometime.  Thank you. 
> 
> But I feel a little danger because Hash does not have any checking
> mechanism to detect multiple values.  At least it should be documented
> in the reference manual.

To be fair, the example does show it:

  dave[14:58:19] ri invert
  ----------------------------------------------------------------------
     hsh.invert -> aHash
  ----------------------------------------------------------------------
     Returns a new hash created by using hsh's values as keys, and the
     keys as values.

        h = { "n" => 100, "m" => 100, "y" => 300, "d" => 200, "a" => 0 }
        h.invert   #=> {200=>"d", 300=>"y", 0=>"a", 100=>"n"}


Should we make it more explicit?


Dave