Finding silent errors

Loud errors are the nice ones: the housing names the error and the line, you fix it, done. The dangerous ones are errors where the chip happily keeps running and still does nonsense. The tank cooling never starts, the display shows 320 instead of 47, and nothing lights up anywhere.

NaN and −inf spread#

Every calculation with NaN gives NaN again, and every comparison with NaN gives 0. So sgt on t LIMIT is 0, the cooling stays off. With −inf it is trickier: sgt gives 0, but slt gives 1. A heater that switches on “below the limit” then runs forever.

One line catches both if the value is a temperature in Kelvin:

lbn tmax ANALYSE HASH("Tank") Temperature Maximum
sgt ok tmax 0      # Kelvin is always above 0, NaN and -inf never

The silent program end#

If the chip runs past the last line, it stops forever. No error, no light. Typical causes: forgetting the j start at the end, a conditional jump to a label at the very bottom with nothing after it, or a label in a relative jump. The checker in the IC10 coder warns about it, in the game you only notice it because the system no longer reacts.

Wrong units#

A limit of 40 “degrees” is 40 Kelvin for the chip, so −233 °C. Every tank is warmer, the cooling always runs. You only see mistakes like this when you look at the value next to the limit.