Remembering Values

A var keeps its value until a handler changes it. The value stays through other presses and other players’ actions, and when the world is saved and loaded again.

Contents

• Code
• Run
• Under the Hood: let and var
• Use it: a press-count sign
• Make

button Held -> chip pressed
chip text -> decal Text

Code

@left in pressed: exec
var count: int = 0
@right out text = "Pressed ${count.Value} times"

on pressed {
  count += 1
}

var count: int = 0 is a whole number that starts at 0. count += 1 adds one to it. "Pressed ${count.Value} times" builds text with the count in the middle. String Interpolation has the details.

What does the sign say after three presses?

Run

1. Compile the chip and paste it in-game. Place a Button and a brick with a Text Decal.
2. Wire the Button’s Held to pressed, and text to the Text Decal’s Text input.
3. Press the button a few times. The sign counts.

Under the Hood: let and var

A let is a name for a wire. It holds nothing. Its value is whatever its gates compute right now. A var is a Variable gate that holds a value until a handler writes a new one.

There are two ways to read a var:

• count.Value, outside a handler, is a pure wire from the Variable gate. After a handler writes it, this wire shows the new value on the next tick, the game’s next update.
• count, inside a handler, reads the variable at that step of the chain. A step after a write sees the new value.

@left in pressed: exec
var count: int = 0
var last: int = 0
@right out shown = last.Value

on pressed {
  count += 1
  last = count
}

Inside the handler, last = count runs after count += 1, so it copies the new count.

A var can hold other kinds of value too. var shown: string = "" holds text, and a handler can write a whole message into it: shown = "Welcome".

Use it: a press-count sign

The first example is already a useful part: a visitor counter for a door, or a score for a button game.

Make

Make a sign that counts presses of one button and resets to 0 when a second button is pressed.

button1 Held -> chip pressed
button2 Held -> chip reset
chip text -> decal Text

Next: Reacting to the Game.