let: giving a value a name
let name = "Ada"
let score = 0
let finished = false
let declares one new name in the current lexical scope. The initializer is
evaluated before the name becomes visible, so a declaration cannot refer to
itself:
let score = score + 1 # invalid unless an outer score is visible
There is no declaration without an initializer and no type-annotation syntax.
Example
# language: en
let score = 10
let bonus = score + 5
say score, bonus