array_methods/pickings_and_search.rb

tests/_examples/array_methods/pickings_and_search.rb in the metorex repository.

# The ways elements can be picked out of an array, and the search that halves
# a sorted array rather than walking it.
numbers = [1, 2, 3, 4]

p numbers.combination(2).to_a
p numbers.combination(0).to_a
p numbers.combination(3).size
p numbers.permutation(2).to_a
p numbers.permutation.size
p numbers.repeated_combination(2).size
p [10, 11].repeated_combination(2).to_a
p [10, 11].repeated_permutation(2).to_a
p [10, 11].repeated_permutation(3).size

p [1, 2].product([3, 4], [5])
p [1, 2].product
p [1, 2].product([])

collected = []
numbers.combination(2) { |pair| collected.push(pair) }
p collected.size
p numbers.combination(2) { |pair| pair }.equal?(numbers)

sorted = [0, 1, 3, 4]
p sorted.bsearch { |number| number >= 2 }
p sorted.bsearch { |number| number >= 9 }
p sorted.bsearch_index { |number| number >= 2 }
p sorted.bsearch { |number| number <=> 3 }
p sorted.bsearch { |number| number <=> 2 }
p [1].bsearch.class

Output:

[[1, 2], [1, 3], [1, 4], [2, 3], [2, 4], [3, 4]]
[[]]
4
[[1, 2], [1, 3], [1, 4], [2, 1], [2, 3], [2, 4], [3, 1], [3, 2], [3, 4], [4, 1], [4, 2], [4, 3]]
24
10
[[10, 10], [10, 11], [11, 11]]
[[10, 10], [10, 11], [11, 10], [11, 11]]
8
[[1, 3, 5], [1, 4, 5], [2, 3, 5], [2, 4, 5]]
[[1], [2]]
[]
6
true
3
nil
2
3
nil
Enumerator