On Saturday, 16 May 2015 at 09:36:30 UTC, Per Nordlöw wrote:
After having written a lot of text pattern matching functions
using Phobos' findSplit, findSplitBefore, findSplitAfter, and
some more I've written myself I've come to the conclusion that
I would like to enhance these functions to instead return a
struct instead of tuples. This struct would typically look like
struct FindSplit(T)
{
T[3] data;
T first() { return data[0]; }
T separator() { return data[1]; }
T second() { return data[2]; }
T opIndex(size_t i) return { return data[i]; }
cast(T : bool)() { return !separator.empty; }
}
This would enable the following useful syntax:
if (const split = line.findSplit(`-`))
{
// do something with split
}
instead of current
const split = line.findSplit(`-`)
if (!split[1].empty)
{
}
which is a constantly reoccurring pattern in D code processing
text.
The cons I can think of is that split[N] (N being a
CT-constant) will occurr in run-time instead of compile-time
and of course that people relying on that return-type of
findSplit() being a tuple will cause code-breakage.
What do you guys think;
- Add extra template-param that returns struct instead and make
the current behaviour deprecated?
- Will happen for D3? :)
- Will never happen?
Destroy!
It can be implemented in a backwards-compatible way as a subtype
of a Tuple.
struct FindSplit(R)
{
Tuple!(R, "pre", R, "separator", R, "post") asTuple;
bool opCast(T : bool)()
{
return !asTuple.separator.empty;
}
alias asTuple this;
}
Tuple!(R, "pre", R, "separator", R, "post") is a subtype of
Tuple!(R, R, R), which should be the current return type.
