> нет, унарное сложение - есть ваша конкатенация. В детском саду вас учили
> на палочках складывать?
> | - 1
> || - 2
> ||| - 3
> || + ||| = |||||

Для палочек + коммутативен. Для строк нет.

> https://docs.julialang.org/en/v1/manual/strings/#man-concate...
> In mathematics, + usually denotes a commutative operation, where the order of the operands does not matter. An example of this is matrix addition, where A + B == B + A for any matrices A and B that have the same shape. In contrast, * typically denotes a noncommutative operation, where the order of the operands does matter. An example of this is matrix multiplication, where in general A * B != B * A. As with matrix multiplication, string concatenation is noncommutative: greet * whom != whom * greet. As such, * is a more natural choice for an infix string concatenation operator, consistent with common mathematical use.

Хотя другие математики (haskell) конкатят списки (и строки) через ++