Right, they are only approximately comparable, but the important thing to remember is that features of formalisms are never goals in themselves, but rather means to various ends. The goal is never "to have interfaces/typeclasses/traits" but to be able to specify an algorithm that works for a variety of data structures with shared properties. Moreover, I think it would be a mistake for Zig library authors to try and replicate styles used in other languages. Zig provides sufficient mechanisms for expressing programs, and it will develop its own style. There will be elements that are analogous to those in other lanugages, but not identical.

Having said that, I do support a proposal for specifying a type at the parameter declaration with some type -> bool function.

I like this quote by Leslie Lamport about comparing formalisms (he talks about specification languages rather than programming languages, but the sentiment is the same):

> Comparisons between radically different formalisms tend to cause a great deal of confusion. Proponents of formalism A often claim that formalism B is inadequate because concepts that are fundamental to specifications written with A cannot be expressed with B. Such arguments are misleading. The purpose of a formalism is not to express specifications written in another formalism, but to specify some aspects of some class of computer systems. Specifications of the same system written with two different formalisms are likely to be formally incomparable… Arguments that compare formalisms directly, without considering how those formalisms are used to specify actual systems, are useless.