On 07/08/2014 05:13 PM, "Nordlöw" wrote:
> If I want randInPlace to take value arguments (such as structs) by
> reference and reference types (classes) as normal is this
I don't understand what it means to fill a struct or a class object with
random content.
> /** Generate Random Contents in $(D x).
> */
> auto ref randInPlace(T)(auto ref T x) @safe /* nothrow */ if
(isIterable!T)
hasAssignableElements is more correct.
> {
> foreach (ref elt; x)
> {
> import std.range: ElementType;
> static if (isInputRange!(ElementType!T))
The documentation of hasAssignableElements mentions that it implies
isForwardRange and it makes sense: You don't want the range to be
consumed as an InputRange would do.
> elt[].randInPlace;
> else
> elt.randInPlace;
> }
> return x;
> }
> And how does this compare to using x[].randInPlace() when x is a static
> array?
Range algorithms don't work with static arrays because they can't
popFront(). The solution is to use a slice to the entire array as you've
already done as x[]. ;)
> Does x[] create unnecessary GC-heap activity in this case?
No. Static array will remain in memory and x[] will be a local slice. A
slice consists of two members, the equivalent of the following:
struct __SliceImpl
{
size_t length;
void * pointer_to_first_element;
}
> I'm wondering because (auto ref T x) is just used in two places in
> std.algorithm and std.range in Phobos. Is this a relatively new
> enhancement?
Phobos algorithms use ranges. The following is what I've come up with
very quickly:
import std.stdio;
import std.range;
import std.traits;
import std.random;
void randInPlace(R)(R range)
if (hasAssignableElements!R)
{
foreach (ref e; range) {
e.randInPlace();
}
}
void randInPlace(E)(ref E element)
if (isNumeric!E)
{
// BUG: Never assigns the value E.max
element = uniform(E.min, E.max);
}
void randInPlace(E)(ref E element)
if (isBoolean!E)
{
element = cast(bool)uniform(0, 2);
}
void main()
{
auto arr = [ [ 0, 1, 2 ], [ 3, 4, 5 ] ];
arr.randInPlace();
writefln("%s", arr);
auto barr = [ [ false, true ], [ false, true ] ];
barr.randInPlace();
writefln("%s", barr);
}
Ali
