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Tutorial · Grade 128. Even or Odd

Send each even number to the Even Block. Send each odd number to the Odd Block.

Scenario

Number cards arrive one at a time. Each number is either even or odd.

Problem statement

Welcome to the number desk.

Number cards arrive one at a time. Your job is to put each card in the right block.

Even numbers go to the Even Block. An even number can be split into two equal halves, like 2, 4, 6 and 8.

Odd numbers go to the Odd Block. An odd number cannot be split into two equal halves, like 1, 3, 5 and 7.

The desk checks each item for you, so you do not need to do any maths. You can see the facts it gives you in the Conditions tab.

Right now there are no rules. The cards wait and nothing moves.

Your task: build a rule that sends every even number to the Even Block. Then build a rule that sends every odd number to the Odd Block.

Every whole number is either even or odd. So each card belongs in exactly one block.

What this teaches

How to use a fact about a number to choose between two blocks.

Scroll down to build and test your solution.

Active controller

Apply & Run executes only the selected controller.

How a rule works

A rule has two parts:

WHEN <something is true> → DO <this action>

  • WHEN is a question about what is happening right now. For example: "Is it raining?" or "Is there a wall ahead?"
  • DO is what happens when the answer is yes.
  • The simulation runs one step at a time.
  • On each step, the rules are checked from top to bottom.
  • The first rule that is true wins. The rules below it are skipped for that step.
  • To change which rule wins, move it up or down the list.
  • If no rule is true, nothing happens on that step.
  • Some actions have more than one step, like "turn right, then move". You build these in the Functions tab.
  • Once a multi-step action starts, it finishes all its steps before the rules are checked again. It only stops early if the next step is not safe.
See an example

Two rules for deciding about an umbrella:

1  WHEN isRaining  → take an umbrella
2  WHEN always     → leave the umbrella at home
  • It is raining. Rule 1 is true, so you take an umbrella. Rule 2 is skipped.
  • It is sunny. Rule 1 is false, so rule 2 is checked next. Rule 2 is always true, so you leave the umbrella at home.
  • Order matters. If rule 2 were on top, it would be true every day, and you would never take an umbrella.

Rule folders

Categorise cards without changing their global execution order.

No rules yet. Nothing will happen until you add at least one rule.