From: Colin Bartlett <colinb2r@...>
Date: 2010-06-04T03:48:49+09:00
Subject: Re: Split text into equal characters but keeping whole words

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On Thu, Jun 3, 2010 at 10:19 AM, John Butler <johnnybutler7@gmail.com>wrote:

> I have text that is pretty large.  What i want to do is split it into an
> array of no more than 250 characters per line but finishing on a full
> word at the end of each line.  So if the last word was "ruby" but 'b'
> was the 250th character in the line then i want the line to cut off
> before ruby and then start at ruby for the next line. ... Any ideas?
>

Using as an example the text below (setting to one side my slight surprise
that Warren Buffett knows the quote by Jacobi), and ignoring any edge cases
and subtle issues mentioned by Ian Hobson and David A Black, an idea might
be:
* go through the text adding 250 (or whatever) to the "latest" end position;
* use rindex and David Black's suggestion of the \b anchor
  to search *backwards* for the "first" previous word boundary;
* a refinement is use that as a "first guess" for the next split position,
  and then see if any edge cases or issues raised by Ian Hobson
  should make the split position "earlier". (But once you're doing
  that, it might perhaps be better to use Ian Hobson's suggestion
  of going forwards one word at a time and checking if it will fit,
  or if there is a paragraph break, etc.)

    def split_on_words_with_max_line_length( text, max_line_length )
      text_last_index_plus_1 = text.length
      ii = nil ; jj = 0; aa = []
      while true
        ii = jj; jj = ii + max_line_length
        if jj < text_last_index_plus_1 then
          ww = text.rindex( %r{\b}m, jj )
          jj = ww # done like this in case jj needed for edge cases
        else
          jj = text_last_index_plus_1
        end
        aa << text[ ii ... jj ].strip
        break  unless jj < text_last_index_plus_1
      end
      aa
    end

text =
  "http://en.wikipedia.org/wiki/Carl_Gustav_Jacob_Jacobi" \
  " Carl Gustav Jacob Jacobi (10 December 1804 - 18 February 1851)" \
  " was a Prussian mathematician, widely considered to be" \
  " the most inspiring teacher of his time and one of" \
  " the greatest mathematicians of all time." \
  " ... It was in algebraic development that Jacobi's peculiar power" \
  " mainly lay, and he made important contributions of this kind" \
  " to many areas of mathematics ... One of his maxims was:" \
  " 'Invert, always invert' ('man muss immer umkehren')," \
  " expressing his belief that the solution of many hard problems" \
  " can be clarified by re-expressing them in inverse form." \
  "\n\n" \
  "http://www.ibtimes.com/articles/20100227/" \
  "invert-always-invert-buffet-advises-shareholders.htm" \
  " In his annual letter to shareholders, legendary investor" \
  " Warren Buffett outlined a few approaches to investing" \
  " and business management that should be avoided." \
  " Buffett cited Jacobi, a mathematician, who advised problem solvers" \
  " to \"invert, always invert\". In other words, instead of trying" \
  " to find ways of doing something successfully, first find methods" \
  " that are likely fail and avoid them."

max_line_length = 102 # or whatever
puts text
puts; puts split_on_words_with_max_line_length( text, max_line_length )

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