Course five

Stir Until Done

On the menu: loops — doing a thing over and over until the kitchen timer hits zero.

Every recipe repeats itself

“Knead until smooth.” “Stir until thickened.” Real recipes are full of do-this-until instructions, so Chef's loops look exactly like that. A loop is a matched pair of sentences wrapped around a body:

Launch the rocket.
  [ the loop body — any instructions ]
Launch the rocket until launched.

Here's the mechanism, piece by piece:

• The opening sentence — any verb plus an ingredient. Chef checks the ingredient: if it's zero, the whole loop is skipped; otherwise the body runs.
• The closing sentence — repeats the verb as “until verbed” (launch → launched, bake → baked, beat → beaten… Chef speaks fluent grammar). When the recipe reaches it, it jumps back and checks the opening ingredient again. Still not zero? Another lap.
• The secret handshake — if the closing sentence names an ingredient, that ingredient is lowered by 1 every lap. Name the same ingredient in both sentences, and you've built a kitchen timer: 5, 4, 3, 2, 1, ding.

(Fine print for future chefs: the ingredient that gets checked is the one in the opening sentence, and the one that gets decremented is the one in the closing sentence. They're usually the same — but they don't have to be, and fancy recipes exploit that.)

The sticky-numbers problem

Before we cook: a warning from course one. When Chef prints several dry numbers, it prints them back to back — a countdown would come out as 54321, which reads more like a zip code than a launch. The fix is pure kitchen logic: put something liquid between them. Water! An ingredient declared as 32 ml water is liquid with value 32 — and 32 is the character code for a space. One splash between every number keeps the plate tidy. (Same trick, different flavor: 10 ml of anything prints as a newline.)

Tonight's recipe: Rocket Salad Countdown

Rocket is a salad leaf (ask a British greengrocer), which makes Launch the rocket. a completely legitimate cooking instruction. This dish prints a five-second countdown and lifts off.

Rocket Salad Countdown.

A zesty salad that counts down from five and launches itself off the plate. A splash of water between the numbers keeps them from sticking together.

Ingredients.
5 g rocket
0 g sugar
1 g salt
32 ml water
76 g lentils
105 g iceberg lettuce
102 g figs
116 g tomatoes
111 g olives
33 g chili flakes

Method.
Put chili flakes into the mixing bowl. Put figs into the mixing bowl. Put figs into the mixing bowl. Put olives into the mixing bowl. Put tomatoes into the mixing bowl. Put figs into the mixing bowl. Put iceberg lettuce into the mixing bowl. Put lentils into the mixing bowl. Liquefy contents of the mixing bowl. Launch the rocket. Put water into the mixing bowl. Put salt into the mixing bowl. Add sugar to the mixing bowl. Fold sugar into the mixing bowl. Put sugar into the mixing bowl. Launch the rocket until launched. Pour contents of the mixing bowl into the baking dish.

Serves 1.

5 4 3 2 1 Liftoff!

How the countdown cooks

Phase one — the message. The first eight Puts spell Liftoff! backwards into the bowl (course two technique: last in, first out), and Liquefy contents melts those eight letters. They'll sit at the bottom of the pile, ready to print last.

Phase two — the loop. rocket starts at 5, so the body runs five times, and the closing sentence lowers the rocket by 1 each lap. Inside the body, a clever little four-step builds the numbers 1, 2, 3, 4, 5:

(That Fold is a sneak preview of course six — it's the opposite of Put: it takes the top value out of the bowl and stores it in an ingredient.) So sugar climbs 1, 2, 3, 4, 5 as the rocket ticks 5, 4, 3, 2, 1 — and because each new number lands on top of the pile, serving prints them biggest-first: 5 4 3 2 1, then the melted letters underneath: Liftoff!