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Capture a multiplier

YOUR TASK

Make this happen

3 steps

  1. A closure retains access to variables in its surrounding scope. Return a function that multiplies its argument by the captured factor.

  2. Read the cases in lesson.test.lua, then choose Check solution to see what needs to change.

  3. Update subject.lua until every test passes. Keep the supplied tests unchanged.

Start with Check solution, then use the failures to guide your edits.

Read the starter and tests

subject.lua

exports.multiplier = function(factor: number): (number) -> number
  return function(value: number): number
    return value
  end
end

lesson.test.lua

local t = require("test")
local subject = require("cococo.subject")

t.it("captures factor", function()
  local s = subject.load()
  local triple = s.multiplier(3)
  t.expect(triple(4)):eq(12)
end)

t.it("independent closures", function()
  local s = subject.load()
  local twice = s.multiplier(2)
  local five = s.multiplier(5)
  t.expect(twice(3)):eq(6)
  t.expect(five(3)):eq(15)
end)