I also spend some time with stored procedure programming, mostly PL/SQL, most of them are also Ada based, and I find them quite productive, actually.

When you say constrained types do you mean generics? You have generics and concepts (similar to C++17) in Nim, not too sure about Ada.

I meant types with constraints, like this one: sum :: Num a => [a] -> a The type variable a is constrained to have implementation of interface Num (integer constant (0), addition, subtraction, etc).

These constraints can be much deeper. For example, I can define a function that allow me to add two somethings if their "regions" (a property I know how to compute) is equal and the result will be produced in "region" of first argument: add :: (Region a ~ Region b, Region a ~ Region c) => a -> b -> c

One use of something similar is addition of integer values represented by bit vectors in Verilog - you should not add bit vectors from different clock domains, otherwise you get unpredictable results.