abstract algebra is foundation for a) arithmetic as applied to 'Classes'. Eg overloading arithmetic operators that work on custom classes -- is, in a way, wha

abstract algebra is foundation for a) arithmetic as applied to 'Classes'. Eg overloading arithmetic operators that work on custom classes -- is, in a way, what abstract algebra does . b) Interval arithmetic. For example alen algebra applied to arithmetic of time intervals c) relational database theory as relates to various ways to construct functions on relations. d) type theory (see https://homotopytypetheory.org/book/ https://homotopytypetheory.org/book/ ) e) combinatorics and linear programming (basically being able to express recursive and generative constructs, and reason about them).