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This program prints out Pascal's triangle.

puts (0...10).reduce([[1]]) { |a,x|

a.unshift a.first.reduce([0,[]]) { |b,y|

[y,b.last << (b.first + y)]

}.last + [1]

}.reduce([]) { |c,z|

next [z[z.length/2].to_s.length*2,z.length,\"\"] if c.empty?

[c[0],c[1], z.map { |j|

j.to_s.center(c[0])

}.join('').center(c[0]*c[1])+\"\\n#{c.last}\"]

}.last

I found it on the internet at kellegous.com. How does such a complex program get encoded in 10 lines of code? Use this book to learn how to use map, reduce, and select with Ruby to solve data processing problems. Use this book along with a computer wth Ruby installed, a text editor, and the irb (interactive Ruby) prompt. As you read, type in the code, run the code and ponder the results. Tweak the code to test the code and the results. This book will walk you through problems and solutions which are effective because they use map, reduce, and select. You will gain a deeper understanding on how to break data processing problems into processing stages, each of which is understandable, debuggable, and composable, and how to combine the stages to solve your data processing problem.

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