Add filter(func) method

[GlenHertz]

No description provided.

[GlenHertz]

I guess I'd need to add some tests. But please let me know if this feature is acceptable.

[sostock]

Suggested change

	This functionality requires at least Julia 1.8
	This method requires at least Julia 1.8.

[GlenHertz]

Thanks.

[jakobnissen]

If this is to be done, I think it should be done consistently for filter, Iterators.filter, map, Iterators.map, reduce, mapreduce, foldl and foldr.

[simeonschaub]

If this is to be done, I think it should be done consistently for filter, Iterators.filter, map, Iterators.map, reduce, mapreduce, foldl and foldr.

See #35293

[JeffBezanson]

From triage: we can't do this for map because the 0-collection case is useful (this has been discussed before). However it can be done for all the other listed functions.

• For mapreduce I assume you'd need to pass two functions up front? The result should always be a 1-argument function that accepts a collection/iterator.
• reduce, foldl, and foldr also need to accept an init keyword arg (on the first call, IMO).
• Idea from @StefanKarpinski : add mapper(f) to handle the x->map(f, x) case.

[GlenHertz]

Nice!

[GlenHertz]

Is this good to go now?

[ViralBShah]

Bump. Merge?

[mcabbott]

Should be 1.9 right?

[StefanKarpinski]

Suggested change

	!!! compat "Julia 1.8"
	This method requires at least Julia 1.8.
	!!! compat "Julia 1.9"
	This method requires at least Julia 1.9.

[StefanKarpinski]

Was hoping that GitHub provides a way to make a new PR from a comment like this. Alas...

[StefanKarpinski]

Created the old fashioned way: #47045.