Data manipulation example (table inversion)

Special Variables and Pseudo-Variables example from a Well House Consultants training course
More on Special Variables and Pseudo-Variables [link]

This example is described in the following article(s):
• Ruby - a teaching example showing many of the language features in short but useful program - [link]

Source code: answer Module: R110

# Sample program to show data reformatting capabilities of Ruby.
# See associated blog article for complete description of every line

# Written during a training course given by Well House Consultants

fh = File.new "requests.xyz"
langs = {}

while fh.gets
        chomp!
        fields = split(/[, ]+/)
        name = fields.shift
        for lang in fields
                langs[lang] ||= []
                langs[lang].push name
        end
end

for lang in langs.keys.sort
        langs[lang].sort!
        puts "#{lang}: #{langs[lang].join " "}".gsub(/(.{60,}?)\s/,"\\1\n ")
end

__END__

munchkin:lruby grahamellis$ ruby answer
ASP: barbara delia ethel florence hazel jenny leane nina olivia
   petra queenie rita venus wendy xena zoe
Java: barbara barry cherry david delia ed florence fred graham
   harry iris ivan john ken leane len morris nigel peter rupert
   tina tommy ulsyees uva venus xavier xena zachary
MySQL: adam antonia charles cherry ethel fred gloria iris ivan
   kerry len margaret olivia orpheus queenie rupert sally uva victor
   wendy yollanda zachary
PHP: antonia barry delia ed florence harry hazel john leane morris
   nigel olivia peter quentin rita steve ulsyees uva william xavier
   xena yuri zoe
Perl: adam antonia barry charles cherry david ed ethel fred gloria
   graham hazel iris ivan jenny john ken kerry leane len margaret
   morris nigel nina peter petra queenie quentin rita sally steve
   tommy ulsyees uva venus victor wendy william xavier xena yuri
   zoe
Python: adam barry harry hazel ken leane nigel olivia rupert
Ruby: barbara charles cherry ed florence hazel ivan jenny kerry
   len margaret nina orpheus petra queenie quentin rita steve tina
   venus victor william yollanda zoe
Tcl/Tk: adam antonia barbara charles david ethel gloria graham
   iris ivan ken kerry margaret morris nina orpheus petra quentin
   sally steve tina victor wendy yollanda yuri zachary
XML: antonia barry delia fred gloria jenny john margaret orpheus
   petra sally tommy xena yuri
munchkin:lruby grahamellis$

Learn about this subject

This module and example are covered on the following public courses:
* Learning to program in Ruby
* Ruby Programming
Also available on on site courses for larger groups

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