Modular•13mo ago

Why doesn't fn() coerce to fn() capturing

This works thanks to the signatures being different:

fn first(self, where: fn(T) -> Bool) -> Optional[T]:
    for item in self:
        if where(item): return item
    return Optional[T]()
    
fn first(self, where: fn(T) capturing -> Bool) -> Optional[T]:
    for item in self:
        if where(item): return item
    return Optional[T]()

fn first(self, where: fn(T) -> Bool) -> Optional[T]:
    for item in self:
        if where(item): return item
    return Optional[T]()
    
fn first(self, where: fn(T) capturing -> Bool) -> Optional[T]:
    for item in self:
        if where(item): return item
    return Optional[T]()

However it's still annoying to duplicate every function twice.

3 Replies

Jack Clayton•13mo ago

Thanks for the feedback @TeamPuzel I agree! Can you raise a discussion on GitHub here: https://github.com/modularml/mojo/discussions/new?category=ideas

TeamPuzel•13mo ago

Of course, I now moved this to discussions.

Jack Clayton•13mo ago

Awesome thanks! link here for anyone asking the same question: https://github.com/modularml/mojo/discussions/678

GitHub

coerce fn() to fn() capturing · modularml mojo · Discussion #678

When writing a List implementation this became a problem for functions like map filter or fold: fn first(self, where: fn(T) -> Bool) -> Maybe[T]: for item in self: if where(item): return item...

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Why doesn't fn() coerce to fn() capturing