On Friday, 14 February 2014 at 19:24:58 UTC, Marc Schütz wrote:
On Friday, 14 February 2014 at 16:16:28 UTC, Robin wrote:
On Friday, 14 February 2014 at 15:21:04 UTC, Jesse Phillips
wrote:
FYI an infinite range is defined to have
struct Infinite {
enum empty = false;
}
You know it will never be empty at compile time.
Hiho,
thank you for this interesting input. =)
Couldn't this be equally possible (also at runtime) with the
following:
struct Infinite {
enum empty_ = false;
bool empty() pure { return empty_; }
}
Yes, but only at runtime. For some things to work, you need to
be able to know it at compile time. `std.range` defines a
template `isInfinite` that checks for this.
This information can be used for some optimizations:
`std.algorithm.count` and `std.range.walkLength` are only
defined for non-infinite ranges (to avoid creating an infinite
loop), `std.algorithm.cartesianProduct` can work with two
infinite ranges using a special enumeration strategy if it can
detect them, `std.range.chain` can optimize index access by
stopping at the first infinite range, `std.range.take` can
always define a length for infinite ranges (even if they don't
have a length property themselves), ...
Another example: The `length` property of ranges. It is
possible to turn builtin slices (dynamic arrays) into ranges by
importing `std.range` or `std.array`. Slices already have a
member field `length` by default. Here you have an example
where it's impossible to define a method `length()`. With
properties, nothing special needs to be done: You can always
use `length` without parens, even if it happens to be a method.
Uhm, ... I thought that enum types for variables are determined
at compiletime and as pure functions aren't affected by
side-effects and cause no side-effects their result should be
determinable at compiletime, too.
Couldn't it be possible again if we just add another getter
method "length()" for the slice's length? Then you would have a
uniform access as length() instead of length (without parens) if
you do it analogiously for all other cases. There is just no
difference in my opinion - the one solution forces an interface
with parens and the other forces an interface without them.
Robin
