On Friday, 29 December 2017 at 20:47:44 UTC, Dukc wrote:
On Friday, 29 December 2017 at 19:38:44 UTC, aliak wrote:
So when I'm dealing with ranges, there're a number of times
where I get the front of the returned result of a set of
operations, but of course there is no front so you get an
runtime access error.
This could be what you want:
auto makeInfinite(Range)(Range ofThis)
{ import std.range;
return ofThis.chain(typeof(ofThis.front).init.repeat);
}
void main()
{ import std.stdio, std.range;
auto testArray = [2, 3, 4].makeInfinite;
foreach(e; testArray.take(5)) e.writeln;
readln(); //stops the console from closing immediately;
}
/+
2
3
4
0
0
+/
Hmm, interesting. Not sure that's what I'm looking for but I like
it anyway :)
I'm more looking to deal with situations like this:
Instead of this:
auto result = range.op!f;
if (!result.empty) {
result.front.method();
}
This:
range.op!f.ifFront.method();
In the above scenario I only want method to be called if the
pipeline resulted in any element left in the range.
On the other hand, I really do not recommend using ranges that
way as a default. Most often you do not want to call front() or
popFront() of an empty range in the first place. So if you end
up doing so accidently, you want to know it. If it just
returned some default value chances would be you never notice
you have a bug. That's why front() in debug mode is usually
programmed to termitate the program when it's called
incorrectly.
True you don't want to call front on empty, but sometimes I only
care to call a method on front if it's there. Where the situation
necessitates the existence of front, and not having a front is
indeed a bug, then you want the program to terminate, yes. But
not otherwise.
