Standardised principled abstractions make for better program composition and better API design. In the Haskell world, APIs are much less adhoc, more consistent

Standardised principled abstractions make for better program composition and better API design. In the Haskell world, APIs are much less adhoc, more consistent and easily understood because of such mathematical abstractions (and the laws they imply, relating operations). Principled abstractions enable many other possibilities too, such as automatic program derivation. In Haskell I do not need to write any code to aggregate nested maps or parse a sudoku board, the compiler knows how to assemble such code automatically from the types.