On 09/12/2013 15:53, Damien Radtke wrote:
I have no idea if it would be feasible in the standard library, but
wouldn't the ideal solution be having one function (e.g. from_utf8())
that could return two possible values, a bare result and an Option?
Letting the compiler decide which version to use based on type inference
like this:
let result: ~str = from_utf8(...);
let result: Option<~str> = from_utf8(...);
Assuming both of them are passed invalid UTF8, then the first version
would fail, but the second version would just return None.
Again, I don't know if it's possible given the current implementation,
but I do think it would be helpful to have a picture of the ideal, and
then decide on whatever solution comes closest.
It is possible to have a generic return value, see for example the
.collect() method of iterators.
https://github.com/mozilla/rust/blob/4e0cb316fc980f00e1b74f3fdb7a842b540be280/src/libstd/iter.rs#L447
But it involves creating a trait, and implementing it for every
supported type. IMO it’s a lot more involved than what we would want for
every operation that may fail on invalid input.
As a side note, even if the standard library sticks with two variants
for each option function, I would prefer the default one return an
Option and have the variant fail on invalid input. Task failure at
runtime is a nastier surprise than an invalid type error at compile
time, especially for new users who aren't entirely sure of the difference.
--
Simon Sapin
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