Is it possible to get the origin of `strs` in `fn name(*strs: String)`?

Minimal repro, LSP shows

invalid call to 'append': method argument #0 cannot be converted from 'List[StringSlice[strs]]' to 'List[StringSlice[strs]]'

Seems like a bug, but maybe there's a proper way to do this?

from utils import StringSlice


fn split(*strs: String):
    var blocks: List[List[StringSlice[__origin_of(strs)]]]
    for s in strs:
        blocks.append(s[].as_string_slice().splitlines())    


fn main():
    split("a", "b", "c")

from utils import StringSlice


fn split(*strs: String):
    var blocks: List[List[StringSlice[__origin_of(strs)]]]
    for s in strs:
        blocks.append(s[].as_string_slice().splitlines())    


fn main():
    split("a", "b", "c")

9 Replies

Martin Vuyk•4d ago

Hey @toasty cool to see my code being used in ways I never imagined 🤣 . No that won't work, you're trying to use the origin of the VariadicList as the origin of the strings themselves. This is a hard limitation of our current origin system, you can't have a heterogeneous list which is what this would need to be to be able to carry the origin of each of the strings inside the VariadicList. Now, what I like about Mojo is that you can point a 🔫 to the compiler's head and say "trust me bro":

from utils import StringSlice


fn main():
    items = List[String]("a", "b", "c")
    alias S = StringSlice[ImmutableOrigin.cast_from[__origin_of(items)].result]
    blocks = List[List[S]](capacity=len(items))
    for s in items:
        blocks.append(
            rebind[List[S]](rebind[S](s[].as_string_slice()).splitlines())
        )
    for item in items:
        print(item[], end=" ")
    print("")

from utils import StringSlice


fn main():
    items = List[String]("a", "b", "c")
    alias S = StringSlice[ImmutableOrigin.cast_from[__origin_of(items)].result]
    blocks = List[List[S]](capacity=len(items))
    for s in items:
        blocks.append(
            rebind[List[S]](rebind[S](s[].as_string_slice()).splitlines())
        )
    for item in items:
        print(item[], end=" ")
    print("")

basically this is the hacky way of binding the origin to the list of strings itself

toastyOP•4d ago

Ahhh okay, now it makes sense with that explanation! I thought it would take a union of all the origins through some magic 😂

Martin Vuyk•4d ago

I have a PR open on nightly which should remove the need for rebind[S](s[].as_string_slice()).splitlines() well probably the VariadicList is a union of the origins now that I think about it

toastyOP•4d ago

I appreciate the examples in coercing Mojo to do what I want haha

Martin Vuyk•4d ago

yeah not very adviced to the general public but I know you want to get other things done lol

toastyOP•4d ago

I wanted to see how far I could go without allocating new strings, but avoiding the deep arcane stuff. I probably won’t implement the origin casting, but good to know nonetheless! Doing a lot of split lines -> iterate over code points -> apply ansi sequences and padding -> rejoin

Martin Vuyk•4d ago

actually it should also remove the need for the shady casting ImmutableOrigin.cast_from[__origin_of(items)].result yep, I know that's a very common use case you might want to copy some code from this PR I want to introduce a lazy iterator over splitlines

toastyOP•4d ago

All of your recent changes have brought it very far 🙏🏾 working with strings has felt much better I’ll take a look, thanks!

Martin Vuyk•4d ago

Thanks a lot 😄 . My goal is to make it feel like Python in that sense. It's one of the things I love most about it

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Programming

Is it possible to get the origin of `strs` in `fn name(*strs: String)`?