Relative with devices: brdse, brdns

A sensor on a pin is optional: if it is attached, the chip should read it, otherwise take a fallback value. With bdns and a label that works. For one or two lines there is the shorter form: brdse and brdns.

Relative depending on the pin#

move temp FALLBACK        # fallback value in case d1 is empty
brdns d1 2                # no device: leave out reading
l temp d1 Temperature

Without a device the chip jumps over the l, and temp keeps the fallback value. With a device it reads and overwrites it. Two lines, no label. As with bdse and bdns, a register holding a ReferenceId may serve as the device.

Short fallback lines#

The pattern is called default first, exception after: first the safe value sits in the register, then comes the line that replaces it only under a condition.

Several optional sensors can be averaged like this. Every block only counts if its sensor is attached:

move total 0
move n 0
brdns d0 4
l t d0 Temperature
add total total t
add n n 1

The distance 4 skips the three lines after it.

Weighing readability#

Relative branches save labels and lines. But they come at a price: whoever reads the code has to count lines, and every inserted line moves the targets. As a rule of thumb: