From: Jim Weirich <jweirich@...>
Date: 2002-07-08T21:24:26+09:00
Subject: Re: is there a better string.each?

>>>>> "George" == George Ogata <g_ogata@optushome.com.au> writes:

    George> We have methods corresponding to the iterator/collector methods to set the 
    George> one that #each points to:  #useBytes, #useChars (or #useCharacters), 
    George> #useWords, #useLines, #usePars (or #useParagraphs).
[...]
    George> s = "abc\ndef\nghi"
    George> s.useChars
    George> s.collect {|char| frob char}  # iterates over chars
    George> s.useLines
    George> s.collect {|line| frob line}  # now it iterates over lines

The only problem I have with this suggestions is that
useChars/useLines/etc are state changing methods that affect the
behavior of "each" later in the program.  Using "useChars" at one
point may break a portion of code that assumes a line by line version
of each.

How about something like this.

    s = "abc\ndef\nghi"
    s.by_chars.collect { |char| frob char }
    s.by_lines.collect { |line| frob line }

The methods by_chars/by_lines return an appropriate adapter object
that does the indicated type of iteration over the target string.
This means that there is no state information in a string that needs
to change.  The original s.each can continue to work as currently
defined to avoid breakage.

-- 
-- Jim Weirich     jweirich@one.net    http://w3.one.net/~jweirich
---------------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct, 
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)