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Ruby - Totally Topical

Ruby supports topicalisation - the $_ variable being set by certain statements when a piece of code such as gets in a while statement isn't assigned, and the the same variable being used in many other methods - and even as the object on which methods run by default - in following code.

Here's a piece of code that does NOT use topicalisation:

while info = DATA.gets
  iparts = info.split(/\s+/)
  next unless info =~ /Ruby/
  puts iparts[-1]
  end
__END__
Ruby is a great language
Python is a good language
Ruby is a type of gem
Python is a species of snake
Ruby is a colour
Woodland is a group of trees


And here is the same piece of code with the default input and pattern matching space left out everywhere that info occurred above. And split defaults to splitting at white space, so that can be simplified too.

while DATA.gets
  iparts = split
  next unless /Ruby/
  puts iparts[-1]
  end
__END__
Ruby is a great language
Python is a good language
Ruby is a type of gem
Python is a species of snake
Ruby is a colour
Woodland is a group of trees


Whichever way I run that:

grahamellis$ ruby gloop1
language
gem
colour
grahamellis$

(written 2006-12-16)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
R110 - Ruby - Special Variables and Pseudo-Variables
  [4682] One line scripts - Awk, Perl and Ruby - (2016-05-20)
  [4502] Reading and parsing a JSON object in Ruby - (2015-06-01)
  [3757] Ruby - a teaching example showing many of the language features in short but useful program - (2012-06-09)
  [2623] Object Oriented Ruby - new examples - (2010-02-03)
  [2613] Constants in Ruby - (2010-02-01)
  [2296] Variable scope - what is it, and how does it Ruby? - (2009-07-18)
  [1891] Ruby to access web services - (2008-11-16)
  [1587] Some Ruby programming examples from our course - (2008-03-21)
  [1586] Variable types in Ruby - (2008-03-21)


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Adding a member to a Hash in Ruby
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Training on Cascading Style Sheets
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Enthusiastic, but ....
Adding a member to a Hash in Ruby
Ruby - Totally Topical
Melksham Quiz
You should think you're first in a hotel room
Ruby v Perl - interpollating variables
puts - opposite of chomp in Ruby
Equality in Ruby - == eql? and equal?
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