On Thursday, 28 June 2018 at 18:03:09 UTC, Ali Çehreli wrote:
On 06/28/2018 10:00 AM, Mr.Bingo wrote:
> But is this going to be optimized?
Not our job! :o)
> That is, a tuple is a range!
Similar to the array-slice distinction, tuple is a container,
needing its range.
> It is clearly easy to see if a tuple is empty, to get the
front,
Ok.
> and to
> pop the front and return a new tuple with n - 1 elements,
which is
> really just the tuple(a sliced tuple, say) with the first
member hidden.
That would be special for tuples because popFront does not
return a new range (and definitely not with a new type) but
mutates the existing one.
Here is a quick and dirty library solution:
// TODO: Template constraints
auto rangified(T)(T t) {
import std.traits : CommonType;
import std.conv : to;
alias ElementType = CommonType!(T.tupleof);
struct Range {
size_t i;
bool empty() {
return i >= t.length;
}
ElementType front() {
final switch (i) {
static foreach (j; 0 .. t.length) {
case j:
return t[j].to!ElementType;
}
}
}
void popFront() {
++i;
}
enum length = t.length;
// TODO: save(), opIndex(), etc.
}
return Range();
}
unittest {
import std.typecons : tuple;
import std.stdio : writefln;
import std.range : ElementType;
auto t = tuple(5, 3.5, false);
auto r = t.rangified;
writefln("%s elements of '%s': %(%s, %)",
r.length, ElementType!(typeof(r)).stringof, r);
}
void main() {
}
Prints
3 elements of 'double': 5, 3.5, 0
Ali
Thanks, why not add the ability to pass through ranges and arrays
and add it to phobos?
