Re: How to append range to array?
On Saturday, 23 May 2015 at 07:03:35 UTC, Vladimir Panteleev
wrote:
int[] arr = [1, 2, 3];
auto r = iota(4, 10);
// ???
assert(equal(arr, iota(1, 10)));
Hopefully in one GC allocation (assuming we know the range's
length).
I tried std.range.primitives.put but its behavior seems a
little mysterious:
This compiles but asserts at runtime:
int[] arr = [1, 2, 3];
arr.put(iota(4, 10));
And this is even weirder, can you guess what it will print?
int[] arr = [1, 2, 3];
arr.put(4);
writeln(arr);
int[] arr = [1,2,3];
auto r = iota(4, 10);
auto app = arr.refAppender;
app.put(r);
assert(equal(arr, iota(1, 10)));
which of course you wrap with something like
auto append(T, R)(ref T arr, R r)
if(is(T : Q[], Q) isInputRange!r);
{
auto app = arr.refAppender;
app.put(r);
return arr;
}
to get
int[] arr = [1,2,3];
auto r = iota(4, 10);
arr.append(r);
assert(equal(arr, iota(1, 10)));
Walter has mentioned that he was interested in adding more
range-awareness to the language, so who knows, maybe this sort of
thing will get sugar at some point.
Re: How to append range to array?
On 5/23/15 4:27 AM, Jonathan M Davis via Digitalmars-d-learn wrote: On Saturday, May 23, 2015 07:03:33 Vladimir Panteleev via Digitalmars-d-learn wrote: int[] arr = [1, 2, 3]; auto r = iota(4, 10); // ??? assert(equal(arr, iota(1, 10))); Hopefully in one GC allocation (assuming we know the range's length). I tried std.range.primitives.put but its behavior seems a little mysterious: This compiles but asserts at runtime: int[] arr = [1, 2, 3]; arr.put(iota(4, 10)); And this is even weirder, can you guess what it will print? int[] arr = [1, 2, 3]; arr.put(4); writeln(arr); For better or worse, put does not append to arrays. It fills them. If you want to append using put, then using std.array.Appender. Yes, think of an array as a buffer. When you put into it, you are overwriting the contents. In addition to using Appender (which BTW will add an allocation), you can extend the array and then fill the extended slice: auto oldlen = arr.length; arr.length += someRange.length; put(arr[oldlen..$], someRange); I wish there was a shorter way to do this... -Steve
Re: How to append range to array?
On Sunday, May 24, 2015 22:13:25 Steven Schveighoffer via Digitalmars-d-learn wrote: On 5/23/15 4:27 AM, Jonathan M Davis via Digitalmars-d-learn wrote: On Saturday, May 23, 2015 07:03:33 Vladimir Panteleev via Digitalmars-d-learn wrote: int[] arr = [1, 2, 3]; auto r = iota(4, 10); // ??? assert(equal(arr, iota(1, 10))); Hopefully in one GC allocation (assuming we know the range's length). I tried std.range.primitives.put but its behavior seems a little mysterious: This compiles but asserts at runtime: int[] arr = [1, 2, 3]; arr.put(iota(4, 10)); And this is even weirder, can you guess what it will print? int[] arr = [1, 2, 3]; arr.put(4); writeln(arr); For better or worse, put does not append to arrays. It fills them. If you want to append using put, then using std.array.Appender. Yes, think of an array as a buffer. When you put into it, you are overwriting the contents. In addition to using Appender (which BTW will add an allocation), you can extend the array and then fill the extended slice: auto oldlen = arr.length; arr.length += someRange.length; put(arr[oldlen..$], someRange); I wish there was a shorter way to do this... Honestly, I think that output ranges need at least a minor redesign. They haven't been used as heavily as input ranges and really aren't ironed out as well. A prime example of this is that output ranges assume that put will succeed, and there's no way to even ask how much room an output range has left or whether a call to put will succeed or not. The current state of things works reasonably well with Appender, but it's abysmal if you're dealing with arrays. - Jonathan M Davis
How to append range to array?
int[] arr = [1, 2, 3]; auto r = iota(4, 10); // ??? assert(equal(arr, iota(1, 10))); Hopefully in one GC allocation (assuming we know the range's length). I tried std.range.primitives.put but its behavior seems a little mysterious: This compiles but asserts at runtime: int[] arr = [1, 2, 3]; arr.put(iota(4, 10)); And this is even weirder, can you guess what it will print? int[] arr = [1, 2, 3]; arr.put(4); writeln(arr);
Re: How to append range to array?
On Saturday, May 23, 2015 07:03:33 Vladimir Panteleev via Digitalmars-d-learn wrote: int[] arr = [1, 2, 3]; auto r = iota(4, 10); // ??? assert(equal(arr, iota(1, 10))); Hopefully in one GC allocation (assuming we know the range's length). I tried std.range.primitives.put but its behavior seems a little mysterious: This compiles but asserts at runtime: int[] arr = [1, 2, 3]; arr.put(iota(4, 10)); And this is even weirder, can you guess what it will print? int[] arr = [1, 2, 3]; arr.put(4); writeln(arr); For better or worse, put does not append to arrays. It fills them. If you want to append using put, then using std.array.Appender. - Jonathan M Davis
Re: How to append range to array?
std.range.chain? Atila On Saturday, 23 May 2015 at 07:03:35 UTC, Vladimir Panteleev wrote: int[] arr = [1, 2, 3]; auto r = iota(4, 10); // ??? assert(equal(arr, iota(1, 10))); Hopefully in one GC allocation (assuming we know the range's length). I tried std.range.primitives.put but its behavior seems a little mysterious: This compiles but asserts at runtime: int[] arr = [1, 2, 3]; arr.put(iota(4, 10)); And this is even weirder, can you guess what it will print? int[] arr = [1, 2, 3]; arr.put(4); writeln(arr);
Re: How to append range to array?
On Saturday, 23 May 2015 at 07:03:35 UTC, Vladimir Panteleev wrote: int[] arr = [1, 2, 3]; auto r = iota(4, 10); // ??? assert(equal(arr, iota(1, 10))); import std.array : array; arr ~ r.array;
Re: How to append range to array?
On Saturday, 23 May 2015 at 08:35:45 UTC, weaselcat wrote: On Saturday, 23 May 2015 at 07:03:35 UTC, Vladimir Panteleev wrote: int[] arr = [1, 2, 3]; auto r = iota(4, 10); // ??? assert(equal(arr, iota(1, 10))); import std.array : array; arr ~ r.array; woops, meant ~= but this is probably fairly inefficient. Working with ranges and arrays at the same time feels really badly designed.
Re: How to append range to array?
On Saturday, May 23, 2015 08:36:47 weaselcat via Digitalmars-d-learn wrote: On Saturday, 23 May 2015 at 08:35:45 UTC, weaselcat wrote: On Saturday, 23 May 2015 at 07:03:35 UTC, Vladimir Panteleev wrote: int[] arr = [1, 2, 3]; auto r = iota(4, 10); // ??? assert(equal(arr, iota(1, 10))); import std.array : array; arr ~ r.array; woops, meant ~= but this is probably fairly inefficient. Working with ranges and arrays at the same time feels really badly designed. It's fine if you're not interchanging them. It sounds like he probably wants to append to an existing array after some set of range operations are done. And that's not really any different from converting a range to an array via std.array.array except that the result ends up on the end of an existing array. The problem is that the output range API doesn't support that, because it treats arrays as buffers to be filled rather than appending to them. So, you probably either end up having to use Appender instead of a naked array, or you have to use foreach and append manually (or you could use std.array.array. and append the result, but I'd be surprised if that weren't less efficient). The problem is when you're trying to do range-based operations and throw array-specific operations in the middle of it. _That_ is what needs to be avoided. - Jonathan M Davis
