feat(semigroup): add partial semigroup

[JalilArfaoui]

I suggest this partial semigroup generator, inspired by struct but that can take partial elements

[JalilArfaoui]

@gcanti Do you have any opinion on this ?

[gcanti]

@JalilArfaoui It seems to me that throughout the codebase, the absence of a value is modeled through Option rather than optional properties. I won't go into the details of this implementation, but adding support for optional properties would be an exception.

In any case, development is frozen until a yet-to-be-determined date when I am clear on which direction to take after finishing developments in the new org @fp-ts.

[JalilArfaoui]

Thanks @gcanti.

I think I undertand your point, but I find partials are useful to work on … «partial data structures», where the absence of value does not mean None, it just mean we don’t care … for instance when trying to merge configuration options or some metadata …

To me Option type and Partial serve different purpose …

I didn’t knew some big changes are in development … I’ll go check out on the Discord

[JalilArfaoui]

OK I just found out https://github.com/fp-ts/core …