get all truthy values in an array within a given limit

Question

I want to get all truthy values in an array (in this example that would be numeric values). But once the limit has been reached I do not want to continue looking for truthy values. My initial thought was to do this:

a.select do |n|

  puts "value #{n}"

  n.is_a? Numeric

end.slice(0..9)



value 1

value 2

value 3

value 4

value 5

value 6

value 7

value 8

value 9

value 10

value 11

value 12

value 13

value 14

value 15

 => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

While it gives me the correct results, it still searches through every record. I want it to stop searching when I hit the limit.

How can I achieve this in Ruby?

Answer 1

This could be achieved with lazy and first - both methods are defined on Enumerable:

(1..20).lazy.select do |n|
  puts "value #{n}"
  n.is_a? Numeric
end.first(10)
#=> value 1
#=> value 2
#=> value 3
#=> value 4
#=> value 5
#=> value 6
#=> value 7
#=> value 8
#=> value 9
#=> value 10
#=> [1,2,3,4,5,6,7,8,9,10]

get all truthy values in an array within a given limit

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