Would takewhile be a natural candidate for IterTools.jl?

[reinermartin]

Would a takewhile function be a natural function to add to IterTools? It consumes a given iterator as long as a given condition is met.

So collect(TakeWhile(Base.Iterators.countfrom(1), x-> x^2 <= 50)) would yield [1, 2, 3, 4, 5, 6].

My own (simplistic?) implementation looks like this:

struct TakeWhile{I}
    xs::I
    cond::Function
end

Base.iterate(it::TakeWhile) = iterate(it.xs)

function Base.iterate(it::TakeWhile, state)
    (val, state) = iterate(it.xs, state)
    it.cond(state) || return nothing
    val, state
end

Base.IteratorSize(it::TakeWhile) = Base.SizeUnknown()

[iamed2]

Yes, although it could also be takeuntil

[reinermartin]

Sure; I was thinking of the Python module itertools, which provides takewhile(). Best is to have both, as this is such a basic functional programming concept.

[iamed2]

Ah well we can choose the Python-similar one then :)

[ararslan]

FWIW takewhile is actually the standard name for this, and is provided in Scheme, C#, Haskell, Java, Kotlin, ...

[ararslan]

Your implementation looks good, I'd just swap the argument order to the constructor so that the function comes first, which is conventional.

[reinermartin]

In the meantime, I have prepared code for takewhile with tests and doc, but I can not 'publish branch' or create a 'pull request'. I get

"Authentication failed. You may not have permission to access the repository or the repository may have been archived. Open options and verify that you're signed in with an account that has permission to access this repository"

if I try to publish from GitHub Desktop. Are there any special rights I need to do this?

Sorry, this is a total beginner's question - I have never contributed to any open source before.

[ararslan]

You can fork the package to your account by clicking "Fork" in the upper right corner of the page, next to "Star" and "Watch." You can then add add your fork as a Git remote, push your changes to your fork, then open a PR based on that.

[reinermartin]

Thanks ararslan, I'll try that now.

[reinermartin]

OK, I created a fork, added my code to three files manually, and created a pull request - first time for me!

[reinermartin]

Oh, "All checks have failed" - would have been too easy... :-(

[reinermartin]

So I fixed (one) bug (copied one 'end' too many) - do I have to create new pull request, or what do I need to do?

[ararslan]

You can commit the changes to your branch then push to the remote again, which will automatically update the existing pull request.

[reinermartin]

If this works out I'll add 'takeuntil' some other day

[iamed2]

If this works out I'll add 'takeuntil' some other day

Don't worry about it :)

[iamed2]

Added in https://github.com/JuliaCollections/IterTools.jl/pull/54

[ararslan]

I have never contributed to any open source before.

Your first contribution was a great one!