Functional Ruby Idioms

Composition

Function composition combines small operations into a larger operation.

composition Composed functions keep each step small while still producing one final result.

Composition

suffix
composition.rb
Replay: real traced execution (multi-file project)
suffix = "!"
trim = ->(text) { text.strip }
upcase = ->(text) { text.upcase }
decorate = ->(text) { "#{text}#{suffix}" }

input = " ruby "
step_one = trim.call(input)
step_two = upcase.call(step_one)
result = decorate.call(step_two)

puts "suffix=#{suffix}"
puts "step_one=#{step_one}"
puts "result=#{result}"

suffix = "?"
trim = ->(text) { text.strip }
upcase = ->(text) { text.upcase }
decorate = ->(text) { "#{text}#{suffix}" }

input = " ruby "
step_one = trim.call(input)
step_two = upcase.call(step_one)
result = decorate.call(step_two)

puts "suffix=#{suffix}"
puts "step_one=#{step_one}"
puts "result=#{result}"

suffix = "."
trim = ->(text) { text.strip }
upcase = ->(text) { text.upcase }
decorate = ->(text) { "#{text}#{suffix}" }

input = " ruby "
step_one = trim.call(input)
step_two = upcase.call(step_one)
result = decorate.call(step_two)

puts "suffix=#{suffix}"
puts "step_one=#{step_one}"
puts "result=#{result}"

  1. suffix ← !, trim ← ⟨Proc A /tmp/execution/⟨tmp B⟩.rb:32 (lambda)⟩

    1suffix→ ! = "!"  #@suffix="?", "."2trim→ ⟨Proc A /tmp/execution/⟨tmp B⟩.rb:32 (lambda)⟩ = ->(text) { text.strip }3upcase→ ⟨Proc C /tmp/execution/⟨tmp B⟩.rb:40 (lambda)⟩ = ->(text) { text.upcase }4decorate→ ⟨Proc D /tmp/execution/⟨tmp B⟩.rb:48 (lambda)⟩ = ->(text) { "#{text}#{suffix}" }56input→  ruby  = " ruby "7step_one→ ruby = trim.call(input)ruby8step_two→ RUBY = upcase.call(step_one)RUBY9result→ RUBY! = decorate.call(step_two)RUBY!1011puts "suffix=#{suffix!}"12puts "step_one=#{step_oneruby}"13puts "result=#{resultRUBY!}"
    outputsuffix=!
step_one=ruby
result=RUBY!

  1. suffix ← ?, trim ← ⟨Proc A /tmp/execution/⟨tmp B⟩.rb:32 (lambda)⟩

    1suffix→ ? = "?"2trim→ ⟨Proc A /tmp/execution/⟨tmp B⟩.rb:32 (lambda)⟩ = ->(text) { text.strip }3upcase→ ⟨Proc C /tmp/execution/⟨tmp B⟩.rb:40 (lambda)⟩ = ->(text) { text.upcase }4decorate→ ⟨Proc D /tmp/execution/⟨tmp B⟩.rb:48 (lambda)⟩ = ->(text) { "#{text}#{suffix}" }56input→  ruby  = " ruby "7step_one→ ruby = trim.call(input)ruby8step_two→ RUBY = upcase.call(step_one)RUBY9result→ RUBY? = decorate.call(step_two)RUBY?1011puts "suffix=#{suffix?}"12puts "step_one=#{step_oneruby}"13puts "result=#{resultRUBY?}"
    outputsuffix=?
step_one=ruby
result=RUBY?

  1. suffix ← ., trim ← ⟨Proc A /tmp/execution/⟨tmp B⟩.rb:32 (lambda)⟩

    1suffix→ . = "."2trim→ ⟨Proc A /tmp/execution/⟨tmp B⟩.rb:32 (lambda)⟩ = ->(text) { text.strip }3upcase→ ⟨Proc C /tmp/execution/⟨tmp B⟩.rb:40 (lambda)⟩ = ->(text) { text.upcase }4decorate→ ⟨Proc D /tmp/execution/⟨tmp B⟩.rb:48 (lambda)⟩ = ->(text) { "#{text}#{suffix}" }56input→  ruby  = " ruby "7step_one→ ruby = trim.call(input)ruby8step_two→ RUBY = upcase.call(step_one)RUBY9result→ RUBY. = decorate.call(step_two)RUBY.1011puts "suffix=#{suffix.}"12puts "step_one=#{step_oneruby}"13puts "result=#{resultRUBY.}"
    outputsuffix=.
step_one=ruby
result=RUBY.