[ddingus]

I think it should be used when one needs a fast, deterministic field of branches.

When I used them, I would use boolean in the math to insure the input value was bounded properly.

X = (Y > 5) and Y (for systems setting true to -1 all bits set)

X = Y * (Y > 5) (for systems setting true to just the value 1)

Basically an in-line compare where the actual numeric value result of the comparison is used in a math expression rather than as an input to an if-then construct.

And these two ideas map directly to assembly language, which given the speed of the machines back in the day, made sense. People were going to be using assembly sooner or later.