How do I access elements in a list by index in DAML?

Question

Say a list has a length of three and I want to access the second, or middle element. What is the best way to do this?

Answer 1

You can use the list index operator !! for this, which is defined as follows:

(!!)
    : [a] -> Int -> a

List index (subscript) operator, starting from 0.

Here's a snipplet demonstrating its usage:

first : [Int] -> Int
first x =
  let f = x!!0
  in f

testFirst = scenario do
  assert(first [3, 2, 1] == 3)