giuseppemag / bccc Goto Github PK

As a programmer interested in adopting more principled methodologies, I absolutely love the ideas you've demonstrated through this library and view it as an extremely valuable resource for learning. Thank you! I really appreciate what you've done here!

I would like to use this as an on-going reference for understanding a subject that tends to allude me (category theory) in terms that I find familiar (mainstream programming languages). As typescript happens to be quite permissive, I can't help but wonder about your decision making process in how you annotated your types. Taking your id function as an example, I can imagine a myriad of ways to annotate it:

• let id = function<a>() : Fun<a,a> { return fun(x => x) } // from your source
• let id = <a>():Fun<a,a> => fun(x => x) // same as above but with arrow function syntax
• let id = <a>() => fun((x:a):a => x) // one variation
• let id:<a>() => Fun<a,a> = () => fun(x => x) // another variation
• let id:<a>() => Fun<a,a> = <a>():Fun<a,a> => fun((x:a):a => x) // multiple variations

Another example that has more obvious effects on usage could be the variety of ways to type a function from a to b:

• type Fun = <a,b>(_:a) => b
• type Fun<a,b> = (_:a) => b
• type Fun<a> = <b>(_:a) => b
• type Fun<b> = <a>(_:a) => b

I can understand that (at least in the first example), the differences may be of trivial importance. At this time, I'm more curious about another, perhaps equally pedantic, decision: is the fun wrapper a necessary implementation detail for achieving current usability?

In terms of typescript, I've always written id as let id = <a>(a:a):a => a. It could be reduced to let id = <a>(a:a) => a, utilizing inference on the return type, or even simply let id = a => a in flow, which utilized flow-based programming. The implications of the fun wrapper reach into other areas, like the semantics of this and ., that are somewhat coupled to the language itself and I'm curious whether your implementation could be further simplified (by removing the fun wrappers) without loss of functionality or if attempting to do so would be a fool's errand.