On Tue, 09 Aug 2011 11:29:52 -0400, Kai Meyer <k...@unixlords.com> wrote:
On 08/08/2011 05:25 PM, Steven Schveighoffer wrote:
On Mon, 08 Aug 2011 18:33:55 -0400, Kai Meyer <k...@unixlords.com> wrote:
On 08/08/2011 12:55 PM, Jonathan M Davis wrote:
I have a problem I'd really like to use Strides for to simplify my
code.
Currently, I do this:
foreach(n; 0..chunks)
comp_arr[n] = values[(n * step_size) + n]
if(!all_same(comp_arr, comp_arr[0]))
It would eliminate an entire 2 lines of code for each time I want
strides, to be able to do this:
if(!all_same(bytes[i..$..step_size])
Meaning, start with i, grab all elements at i + block_size * n until
block_size * n> bytes.length. Right?
-Kai Meyer
Would std.range.stride work for you?
- Jonathan M Davis
It would, if there was a way to give it an offset:
int[] a = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 ];
fixed:
assert(equal(stride(a, 3), [ 1, 4, 7, 10 ][]));
assert(equal(stride(a[1..$], 3), [ 2, 5, 8, 11 ][]));
assert(equal(stride(a[2..$], 3), [ 3, 6, 9 ][]));
assert(equal(stride(a[3..$], 3), [ 4, 7, 10 ][]));
-Steve
Doh, how do I extract the array from the return value of stride?
import std.range;
int do_something(int[] values)
{
return values[0];
}
void main(string[] args)
{
int[] a = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 ];
do_something(stride(a,3));
}
I get:
moo.d(9): Error: function moo.do_something (int[] values) is not
callable using argument types (Result)
moo.d(9): Error: cannot implicitly convert expression (stride(a,3LU)) of
type Result to int[]
Two options, first, you can change do_something to accept a range
(depending on what the real implementation of do_something is, you might
need to require a random-access range, but that dummy implementation could
accept any input range, just return x.front):
int do_something(R)(R values) if (isInputRange!R && is(ElementType!R :
int))
{
return values.front; // maybe need random access in real code?
}
Second option, convert range to an array. This incurs a memory allocation
to create the array:
import std.array;
...
void main(...)
{
...
do_something(array(stride(a, 3)));
}
doc for std.array.array:
http://www.d-programming-language.org/phobos/std_array.html#array
-Steve
