select and detect in Ruby

Filtering a collection down to the elements you actually want.

nums = (1..20).to_a

evens = nums.select { |n| n.even? }
puts evens.inspect

odds = nums.reject(&:even?)
puts odds.first(5).inspect

# detect returns the first match, not all of them
first_big = nums.detect { |n| n * n > 50 }
puts first_big

puts nums.partition { |n| n % 3 == 0 }.inspect

How it works

select keeps matching elements; reject drops them.
detect stops at the first match and returns it alone.
partition splits one array into a matching and a failing half.

Keywords and builtins used here

puts

The run, in numbers

Lines: 13
Characters to type: 288
Tokens: 78
Three-star pace: 80 tpm

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Type this snippet

Step 2 of 3 in Blocks & iterators, step 11 of 29 in Language basics.

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