> I design my code so that I always know which number will be larger than the other.

That’s good discipline, but with better tooling and languages such conditions could be enforced by the compiler such as with Dafny. But Dafny is overkill for those who only want to avoid underflow and overflow without verifying everything else about their program…

That’s what I mean when I lament the state of affairs for underflow. Subtracting numbers is such a basic operation, but for the tech stacks used by most teams it still requires a level of care to avoid errors or corruption. Our industry is building million line behemoth codebases but these basic operations still have to be designed around.

> Typically, in real algorithms, what you want is to not only know the delta, but also which number is larger.

I agree with you, and the article was more concerned about avoiding underflow than actually having a practical use for its various example idioms.

What I’d actually prefer is a guarantee that subtracting two (X) bit numbers results in an (X+1) bit number. A sort of compile-time-checked bignum implementation where the programmer never thinks about the integer sizes or which number is larger until the final step of a calculation. Obviously this gets wasteful when multiplying numbers several times. EDIT: and I’m referring to an abstraction of integer bit sizes in a programming language, I’m not expecting the instruction set or hardware to have arbitrary sized registers.