On Friday, 25 October 2019 at 19:49:05 UTC, Ali Çehreli wrote:
I'm still not completely sold on the whole idea though because
it's not a clear win.
Do others see other advantages in other places like templates?
For example, could templates really be written generically for
arrays and associative arrays?
I'm personally not concerned about generic code.
- The semantics of `in` aren't very well defined anyways.
- Those who write templates like that (hopefully) know what
they're doing, they'll figure it out ;)
- I can't think of situations where you actually want to write
code that generically works on both arrays and associative arrays
like that. (Though if anyone knows one, please share, I'm
interested.)
I'm more concerned about the repeated reports of users being
surprised that `in` doesn't work like they expect. In Python, the
expression `3 in [2, 3, 4]` returns a boolean, and in D you can
do `bool b = 15 in iota(10, 20)` because the operator is
overloaded in Phobos for iota; But as far as actual language
support, `in` is only defined for associative arrays:
https://dlang.org/spec/expression.html#InExpression
It returns a pointer which can be used in an if-statement, but
also to read/modify the value. So should `in` on arrays do the
same? It would be consistent, but usage of raw pointers is
discouraged with the advent of scope and ref etc. Also you can't
implicitly convert a pointer to a boolean.
Should it be a boolean then? That means part of the result of the
linear search is discarded, making `in` less flexible.
So maybe we should leave it for now, and put a small explanation
in the error message.
