Ruby array operations

Iterate over an array, either with or without an index

a = ["a", "b", "c"]

a.each { |x| puts x } => nil

a.map { |x| x + x } => [ "aa", "bb", "cc" ]

a.each_with_index { |x, i| puts "#{i}: #{x}" } => nil

# Outputs:
# 0: "a"
# 1: "b"
# 2: "c"

What is the "right" way to iterate through an array in Ruby? - Stack Overflow

Counting occurences

For a simple boolean case:

responses = [true, false, false, true, true]

yeses = responses.count(true) # => 3

See Ruby/RoR - Count occurrence of an element in an array - Stack Overflow

Enumerable

To start, add to your file:

include Enumerable

each_cons(n)

Used for iterating over a group of elements at the same time

The size of the group is the argument to the function

See Module: Enumerable (Ruby 2.3.1)

.all?

Or, to reduce a list into a boolean for all entries matching a condition:

def all_are_even(list)
    list.all? { |num| num % 2 == 0 }
end

See Module: Enumerable (Ruby 1.8.7)

Duplicate an array, but remove an element given an index

a = ["a", "b", "c"]

b = a.dup.tap{|i| i.delete_at(0)} => ["b", "c"]

ruby - How do I remove an element from an array at a specified index but not do the operation in-place - Stack Overflow