Mary Rose Cook's Practical Intro to FP ported to Ruby

FPinRuby.rb

#
# Squares
#
squares = lambda do |nums|
  nums.map do |num|
    num * num
  end
end

p squares.call([1,2,3,4])


#
# Hash
#
hash = lambda do |items|
  items.map do |item|
    item.hash
  end
end

p hash.call ['Mary', 'Isla', 'Sam']


#
# Sum
#
sum = lambda do |nums|
  nums.reduce(0) do |result, num|
    result + num
  end
end

p sum.call [0, 1, 2, 3, 4]


#
# Count Occurances
#
count_occurances = lambda do |sentences|
  sentences.reduce(0) do |result, sentence|
    result + sentence.scan(/Sam/).count
  end
end

p count_occurances.call(
  ['Mary read a story to Sam and Isla.',
   'Isla Sam cuddled Sam.',
   'Sam chortled.']
)



#
# Assoc dupes a hash and changes an attribute
#
assoc = lambda do |key, value, item|
  new_item = item.dup
  new_item[key] = value
  new_item
end

call = lambda do |fn, key|
  lambda do |item|
    assoc.call(key, fn.call(item[key]), item)
  end
end

set_canada = assoc.curry.(:country, 'Canada')

strip_name = lambda do |item|
  strip = lambda { |name| name.gsub('.', '') }
  call.call(strip, :name).call(item)
end

capitalize_name = lambda do |item|
  capitalize = lambda { |name| name.split(" ").map(&:capitalize).join(" ") }
  call.call(capitalize, :name).call(item)
end

pipeline = lambda do |items, methods|
  methods.reduce(items) do |result, method|
    result.map do |item|
      method.call(item)
    end
  end
end

bands = [{ name: 'sunset rubdown', country: 'UK', active: false },
         { name: 'women', country: 'Germany', active: false },
         { name: 'a silver mt. zion', country: 'Spain', active: true }]

p pipeline.call(bands, [set_canada, strip_name, capitalize_name])