Problem Statement

The Luhn test is used by some credit card companies to distinguish valid credit card numbers from what could be a random selection of digits. Those companies using credit card numbers that can be validated by the Luhn test have numbers that pass the following test:

For example, if the trial number is 49927398716:

Write a function/method/procedure/subroutine that will validate a number with the Luhn test, and use it to validate the following numbers:

Let's start with the solution:

fcn luhnTest(n){
   0 == (n.split().reverse().reduce(fcn(s,n,clk){
      s + if(clk.next()) n else 2*n%10 + n/5 },0,Walker.cycle(1,0)) %10)
}

T(49927398716,49927398717,1234567812345678,1234567812345670)
.apply(luhnTest).println();