Movers and routes

Movers

> < ^ v are movers. Every tick, a mover goes one cell in its direction. When the next cell is not empty, it stops and turns into a bang where it is. If that bang touches a voice, the voice plays.

E is an emitter: every N ticks (its left input) it launches a > to its right. The distance between the emitter and what the arrow hits is a delay:

4E......P4C24

Polyrhythm

Emitters with different periods drift in and out of phase. From the example Movers & polyrhythm:

8E..................P5C02
...................F4
6E..................P5G02
...................F7
cE..................N010
...................Fb
aE..................B3C2o
...................F2

Lanes every 8, 6, 12 (c) and 10 (a) ticks. The bang each arrow turns into also touches the F below it, so each lane flashes the screen in its own colour.

Rails

_ and | are rails. They do nothing by themselves: a mover rides over them, and the rail comes back behind it. _ and | are the same thing, one for horizontal tracks and one for vertical ones. They make your tracks visible even when nothing is playing.

Loops

) turns a mover to its right, ( to its left, from any side. A turn has no input, so all four of its sides stay free, and a track can close into a loop: four turns, some rails and one arrow, and it goes round forever.

As the mover goes round a turn, everything touching that turn gets a bang (from the left, above or below). Put voices around the turns and the loop is a sequencer you can see:

)>_____)P5C14
|......|
|......|
)______)
B2C2

This loop is 7 cells wide and 3 tall, counted from turn to turn, so one lap takes 2 × (7 + 3) − 4 = 16 ticks: exactly one bar. P plays as the arrow goes round the top right turn, B half a bar later at the bottom left. Type a second > on the rails for twice as many hits. Use ) for loops that run clockwise and ( for loops that run the other way: side by side they make mirror images.

Switches

: is a switch. A mover reaching it from the left, the top or the bottom leaves the way the cell on its right says: ^ up, v down, < left, > right, or empty for straight on.

........P4C24
........|
........|
8E______:^

Every 8 ticks an arrow rides the rails, turns up at the switch, and stops under P: a bang. Change ^ into v and the arrows go down instead.

The switch’s cell also takes numbers: 0 left, 1 right, 2 up, 3 down. So a clock, a sequence or a link can change the route while it plays:

8C2
..S^v
...@r
........P4C24
........|
........|&r
8E______:
........|
........|
........B2C2

A clock walks the list ^v and sends it on the link r. &r writes it into the switch: one stream of arrows, two voices, taking turns.

Two rules: leave at least one empty cell between a switch and a voice (the mover needs a tick to turn into a bang), and if the way out is blocked, the mover stops and bangs where it is.

Keeping track

• reset puts every mover back where you typed it and clears the screen, without touching your code. Use it when arrows have piled up or gone astray.
• Select a whole loop by dragging across it, then drag the selection (or Ctrl + arrows): the code moves in one piece.
• The Routes examples build trains, routers and effect boards; Code as art lays out whole programs as pictures, with wheels of rails.