Contents

class String
  # Returns first _n_ separations, where separator is 
  # either nil, a String or a Regexp. If a zero-length
  # record separator is supplied then the string is 
  # split on each character. This is the default.
  # If the record separator is set to <tt>nil</tt>,
  # then the string is split on white spaces (/\s+|\Z/).
  # If the record separator is set to <tt>"\n"</tt>,
  # then the string is split on lines (/\n+|\Z/).
  #
  #   require 'facet/string/first'
  #
  #   "Hello World".first(3)  #=> "Hel"
  #
  #--
  # Should the default pattern be $/ or $; instead?
  #++
  def first(n=1, pattern='')
    pattern = '' if pattern == //
    case pattern
    when ''
      return slice(0,n)
    when "\n"
      pattern = /\n+|\Z/
    when nil
      pattern = /\s+|\Z/
    when String
      pattern = Regexp.new( Regexp.escape( separator ) ) #if String === separator
    end

    i,s,e = 0,0,0
    n.times {
      i = self.index( pattern, s )
      break unless i
      e = i
      s = $~.end(0)
    }
    slice(0...e)
  end
end


#__TEST__

if __FILE__ == $0
  require 'test/unit'
  class TestCase < Test::Unit::TestCase
    def test_first
      assert_equal( "Hel", "Hello World!".first(3) )
      assert_equal( "Hel", "Hello World!".first(3, //) )
      assert_equal( "Hello", "Hello World!".first(1, nil) )
      assert_equal( "Hello", "Hello\nWorld!".first(1, "\n") )
      assert_equal( "Hello\nWorld!", "Hello\nWorld!".first(2, "\n") )
    end
  end
end

Version data entries

3 entries across 3 versions & 1 rubygems

Version	Path
facets-0.7.1	lib/facet/string/first.rb
facets-0.7.0	lib/facet/string/first.rb
facets-0.7.2	lib/facet/string/first.rb