Select, Reject, Collect, Detect, Inject

collect-example.rb

y = [1,2,3,4].collect {|number| number ** 2 }
# y will equal [1, 4, 9, 16]

detect-example.rb

y = [1,2,3,4].detect {|number| number%2 == 0}
# y will equal 2
y = [4,3,2,1].detect {|number| number%2 == 0}
# y will equal 4

inject-example.rb

y = [1,2,3,4].inject(0) {|accumulator, number| accumulator += number}
# y will equal 10 ( 1+2+3+4 )
y = [1,2,3,4].inject(10) {|accumulator, number| accumulator += number }
# y will equal 20, ( 10 as the accumulator initial value + 1+2+3+4 )
y = [1,2,3,4].inject([]) {|accumulator, number| accumulator << number*2 }
# y will equal [2,4,6,8]

reject-example.rb

y = [1,2,3,4].reject{|number| number % 2 == 0}
# y will equal [1,3]

select-example.rb

y = [1,2,3,4].select {|number| number % 2 == 0}
# y will equal [2,4]