Re: attribute length missing in std.array: Appender
Ali Çehreli:
void expandWith(A, R)(ref A arr, R range)
{
foreach (e; range) {
arr ~= e;
}
}
I'd like a function like that in Phobos (with a little
improvement: when the length of the given range is available
inside expandWith, it should first extend the capacity to
increase performance a little). But I'd call it "extend" as in
Python.
Bye,
bearophile
Re: attribute length missing in std.array: Appender
On 11/28/2014 12:44 AM, bearophile wrote:
> Now we have a better syntax for implicit casts:
[...]
> app.put(ubyte(0).repeat.take(5));
Much better! :)
> But I have a question too. What's the best way to append several lazy
> items to a dynamic array? This doesn't work:
>
> void main() {
> import std.array, std.range;
> int[] arr;
> arr.put(only(1, 2, 3));
> }
I don't think there is a better way in Phobos. (?) The following trivial
function would do as long as the array has room at the end, which
requires that it is "safe to append":
void expandWith(A, R)(ref A arr, R range)
{
foreach (e; range) {
arr ~= e;
}
}
void main() {
import std.range;
int[] arr = [ 42 ];
// Ensure that there is room for new elements
arr.reserve(100);
assumeSafeAppend(arr);
const oldPlace = arr.ptr;
arr.expandWith(only(1, 2, 3));
const newPlace = arr.ptr;
assert(newPlace == oldPlace);
}
Ali
Re: attribute length missing in std.array: Appender
Ali Çehreli:
auto app = appender!(ubyte[])();
app.put(cast(ubyte)40);
app.put(cast(ubyte)5);
app.put(cast(ubyte)234);
// ... add 5 times 0
A fancy way: :)
import std.range;
// ...
app.put(repeat(cast(ubyte)0).take(5));
Now we have a better syntax for implicit casts:
void main() {
import std.array, std.range;
Appender!(ubyte[]) app;
app.put(ubyte(0).repeat.take(5));
}
Single line, but not lazy:
void main() {
import std.array, std.range;
Appender!(ubyte[]) app = ubyte(0).repeat.take(5).array;
}
But I have a question too. What's the best way to append several
lazy items to a dynamic array? This doesn't work:
void main() {
import std.array, std.range;
int[] arr;
arr.put(only(1, 2, 3));
}
Bye,
bearophile
Re: attribute length missing in std.array: Appender
On 11/27/2014 08:08 AM, Andre wrote: import std.array: appender; const HEADER_LENGTH = 8; auto app = appender!(ubyte[])(); app.put(cast(ubyte)40); app.put(cast(ubyte)5); app.put(cast(ubyte)234); // ... add 5 times 0 A fancy way: :) import std.range; // ... app.put(repeat(cast(ubyte)0).take(5)); Ali
Re: attribute length missing in std.array: Appender
Thanks a lot for the help. Kind regards André On Thursday, 27 November 2014 at 17:29:50 UTC, Marc Schütz wrote: On Thursday, 27 November 2014 at 16:08:13 UTC, Andre wrote: Hi, I implement a network protocol and use an Appender!(ubyte[])(). I have following issue. The first three bytes I have to fill, the following bytes are reserved and must be 0. In this example the overall header length must be 8. import std.array: appender; const HEADER_LENGTH = 8; auto app = appender!(ubyte[])(); app.put(cast(ubyte)40); app.put(cast(ubyte)5); app.put(cast(ubyte)234); // ... add 5 times 0 // variable length body will follow In case of dynamic array I can simple set the length to 8. Appender doesn't have a length attribute. Is there some other nice D functionaliy I can use? Maybe some functionality in std.array is missing: app.fill(0, HEADER_LENGTH)? Currently I do a work around with a for loop. Kind regards André You can initialize the appender with an existing array, or put an entire array into it at once: import std.array: appender; ubyte[] temp; temp.reserve(8); // reserve first, so that only one allocation happens temp[0 .. 3] = [40, 5, 234]; temp.length = 8; auto app = appender!(ubyte[])(temp); // or: app.put(temp); The array will not be copied when the appender is constructed.
Re: attribute length missing in std.array: Appender
On Thursday, 27 November 2014 at 16:08:13 UTC, Andre wrote: Hi, I implement a network protocol and use an Appender!(ubyte[])(). I have following issue. The first three bytes I have to fill, the following bytes are reserved and must be 0. In this example the overall header length must be 8. import std.array: appender; const HEADER_LENGTH = 8; auto app = appender!(ubyte[])(); app.put(cast(ubyte)40); app.put(cast(ubyte)5); app.put(cast(ubyte)234); // ... add 5 times 0 // variable length body will follow In case of dynamic array I can simple set the length to 8. Appender doesn't have a length attribute. Is there some other nice D functionaliy I can use? Maybe some functionality in std.array is missing: app.fill(0, HEADER_LENGTH)? Currently I do a work around with a for loop. Kind regards André You can initialize the appender with an existing array, or put an entire array into it at once: import std.array: appender; ubyte[] temp; temp.reserve(8); // reserve first, so that only one allocation happens temp[0 .. 3] = [40, 5, 234]; temp.length = 8; auto app = appender!(ubyte[])(temp); // or: app.put(temp); The array will not be copied when the appender is constructed.
attribute length missing in std.array: Appender
Hi, I implement a network protocol and use an Appender!(ubyte[])(). I have following issue. The first three bytes I have to fill, the following bytes are reserved and must be 0. In this example the overall header length must be 8. import std.array: appender; const HEADER_LENGTH = 8; auto app = appender!(ubyte[])(); app.put(cast(ubyte)40); app.put(cast(ubyte)5); app.put(cast(ubyte)234); // ... add 5 times 0 // variable length body will follow In case of dynamic array I can simple set the length to 8. Appender doesn't have a length attribute. Is there some other nice D functionaliy I can use? Maybe some functionality in std.array is missing: app.fill(0, HEADER_LENGTH)? Currently I do a work around with a for loop. Kind regards André
