It's definitely a typo. Conceptually I prefer looking at them as a % b = a - trunc(a / b) * b a %% b = a - floor(a / b) * b The latter is even use

It's definitely a typo. Conceptually I prefer looking at them as a % b = a - trunc(a / b) * b a %% b = a - floor(a / b) * b The latter is even used as % in languages such as Python, which further compounds any syntactical confusion. :D