digitalmars.D.learn - Why .dup not work with multidimensional arrays?
- Dennis Ritchie (28/28) May 07 2015 Hi,
- E.S. Quinn (5/33) May 07 2015 It's because arrays are references types, and .dup is a strictly
- Dennis Ritchie (21/25) May 07 2015 Thank you. It really works :)
- =?UTF-8?B?QWxpIMOHZWhyZWxp?= (29/53) May 07 2015 In D, everything is possible and very easy. :p I called it deepDup:
- Dennis Ritchie (44/73) May 08 2015 Thank you. In D it's really easy :)
- =?UTF-8?B?QWxpIMOHZWhyZWxp?= (17/21) May 08 2015 That's because every template instance is a different type (or
- Dennis Ritchie (2/26) May 08 2015 Thankы. Now everything is clear.
- Chris (3/69) May 08 2015 Nice one. I have the same problem in one of my modules. I might
Hi,
Should the method .dup work with multidimensional arrays for
copying?
-----
import std.stdio;
void main() {
auto a = [1, 2, 3];
auto b = a.dup;
b[] *= 2;
writeln("a = ", a); // [1, 2, 3] // OK
writeln("b = ", b); // [2, 4, 6] // OK
auto c = [[[1, 2, 3], [4, 5, 6, 7, 8]],
[[9, 10], [11, 12, 13]]];
auto d = c.dup;
writeln("d[0][1][1 .. $ - 1] = ",
d[0][1][1 .. $ - 1]);
d[0][1][1 .. $ - 1] *= 3;
writeln("c = ", c);
// [[[1, 2, 3], [4, 15, 18, 21, 8]],
// [[9, 10], [11, 12, 13]]] // wrong
writeln("d = ", d);
// [[[1, 2, 3], [4, 15, 18, 21, 8]],
// [[9, 10], [11, 12, 13]]] // OK
}
-----
http://ideone.com/Ddtm47
I thought the slice of the array c[0][1][1 .. $ - 1] = [5, 6, 7]
not had to change to [15, 18, 21] by multiplying by 3.
May 07 2015
It's because arrays are references types, and .dup is a strictly
shallow copy, so you're getting two outer arrays that reference
the same set of inner arrays. You'll have to duplicated each of
the inner arrays yourself if you need to make a deep copy.
On Friday, 8 May 2015 at 02:15:38 UTC, Dennis Ritchie wrote:
Hi,
Should the method .dup work with multidimensional arrays for
copying?
-----
import std.stdio;
void main() {
auto a = [1, 2, 3];
auto b = a.dup;
b[] *= 2;
writeln("a = ", a); // [1, 2, 3] // OK
writeln("b = ", b); // [2, 4, 6] // OK
auto c = [[[1, 2, 3], [4, 5, 6, 7, 8]],
[[9, 10], [11, 12, 13]]];
auto d = c.dup;
writeln("d[0][1][1 .. $ - 1] = ",
d[0][1][1 .. $ - 1]);
d[0][1][1 .. $ - 1] *= 3;
writeln("c = ", c);
// [[[1, 2, 3], [4, 15, 18, 21, 8]],
// [[9, 10], [11, 12, 13]]] // wrong
writeln("d = ", d);
// [[[1, 2, 3], [4, 15, 18, 21, 8]],
// [[9, 10], [11, 12, 13]]] // OK
}
-----
http://ideone.com/Ddtm47
I thought the slice of the array c[0][1][1 .. $ - 1] = [5, 6,
7] not had to change to [15, 18, 21] by multiplying by 3.
May 07 2015
On Friday, 8 May 2015 at 02:23:23 UTC, E.S. Quinn wrote:It's because arrays are references types, and .dup is a strictly shallow copy, so you're getting two outer arrays that reference the same set of inner arrays. You'll have to duplicated each of the inner arrays yourself if you need to make a deep copy.Thank you. It really works :) ----- import std.stdio; void main() { auto c = [[[1, 2, 3], [4, 5, 6, 7, 8]], [[9, 10], [11, 12, 13]]]; auto d = [[c[0][0].dup, c[0][1].dup], [c[1][0].dup, c[1][1].dup]]; d[0][1][1 .. $ - 1] *= 3; writeln("c = ", c); // [[[1, 2, 3], [4, 5, 6, 7, 8]], // [[9, 10], [11, 12, 13]]] // OK writeln("d = ", d); // [[[1, 2, 3], [4, 15, 18, 21, 8]], // [[9, 10], [11, 12, 13]]] // OK } ----- http://ideone.com/kJVUhd Maybe there is a way to create .globalDup for multidimensional arrays?
May 07 2015
On 05/07/2015 07:39 PM, Dennis Ritchie wrote:On Friday, 8 May 2015 at 02:23:23 UTC, E.S. Quinn wrote:In D, everything is possible and very easy. :p I called it deepDup: import std.stdio; import std.traits; import std.range; import std.algorithm; auto deepDup(A)(A arr) if (isArray!A) { static if (isArray!(ElementType!A)) { return arr.map!(a => a.deepDup).array; } else { return arr.dup; } } void main() { auto c = [[[1, 2, 3], [4, 5, 6, 7, 8]], [[9, 10], [11, 12, 13]]]; auto d = c.deepDup; d[0][1][1 .. $ - 1] *= 3; writeln("c = ", c); // [[[1, 2, 3], [4, 5, 6, 7, 8]], // [[9, 10], [11, 12, 13]]] // OK writeln("d = ", d); // [[[1, 2, 3], [4, 15, 18, 21, 8]], // [[9, 10], [11, 12, 13]]] // OK } AliIt's because arrays are references types, and .dup is a strictly shallow copy, so you're getting two outer arrays that reference the same set of inner arrays. You'll have to duplicated each of the inner arrays yourself if you need to make a deep copy.Thank you. It really works :) ----- import std.stdio; void main() { auto c = [[[1, 2, 3], [4, 5, 6, 7, 8]], [[9, 10], [11, 12, 13]]]; auto d = [[c[0][0].dup, c[0][1].dup], [c[1][0].dup, c[1][1].dup]]; d[0][1][1 .. $ - 1] *= 3; writeln("c = ", c); // [[[1, 2, 3], [4, 5, 6, 7, 8]], // [[9, 10], [11, 12, 13]]] // OK writeln("d = ", d); // [[[1, 2, 3], [4, 15, 18, 21, 8]], // [[9, 10], [11, 12, 13]]] // OK } ----- http://ideone.com/kJVUhd Maybe there is a way to create .globalDup for multidimensional arrays?
May 07 2015
On Friday, 8 May 2015 at 06:30:46 UTC, Ali Çehreli wrote:
In D, everything is possible and very easy. :p I called it
deepDup:
import std.stdio;
import std.traits;
import std.range;
import std.algorithm;
auto deepDup(A)(A arr)
if (isArray!A)
{
static if (isArray!(ElementType!A)) {
return arr.map!(a => a.deepDup).array;
} else {
return arr.dup;
}
}
void main()
{
auto c = [[[1, 2, 3], [4, 5, 6, 7, 8]],
[[9, 10], [11, 12, 13]]];
auto d = c.deepDup;
d[0][1][1 .. $ - 1] *= 3;
writeln("c = ", c);
// [[[1, 2, 3], [4, 5, 6, 7, 8]],
// [[9, 10], [11, 12, 13]]] // OK
writeln("d = ", d);
// [[[1, 2, 3], [4, 15, 18, 21, 8]],
// [[9, 10], [11, 12, 13]]] // OK
}
Ali
Thank you. In D it's really easy :)
Recursion, which works with the lambda map looks fine.
I was a little question: why static int idx variable declared
within a function deepDup takes the values 1, 1, 1, 2, 2, 3, 4,
as opposed to a global variable static int idx, which receives
the expected value of 1, 2, 3, 4, 5, 6, 7 ?
-----
import std.stdio,
std.range,
std.traits,
std.algorithm;
// static int idx; // 1, 2, 3, 4, 5, 6, 7 // OK
auto deepDup(A)(A arr)
if (isArray!A)
{
static int idx; // 1, 1, 1, 2, 2, 3, 4 // Why is this happening?
++idx;
writeln("visited");
static if (isArray!(ElementType!A)) {
writeln("ifIdx = ", idx);
writeln("ifArr = ", arr);
return arr.map!(a => a.deepDup).array;
} else {
writeln("elseIdx = ", idx);
writeln("elseArr = ", arr);
return arr.dup;
}
}
void main() {
auto a = [[[1, 2, 3], [4, 5, 6, 7, 8]],
[[9, 10], [11, 12, 13]]];
auto b = a.deepDup;
b[0][1][1 .. $ - 1] *= 3;
writeln("\nResualt: ");
writeln("a = ", a);
// [[[1, 2, 3], [4, 5, 6, 7, 8]],
// [[9, 10], [11, 12, 13]]]
writeln("b = ", b);
// [[[1, 2, 3], [4, 15, 18, 21, 8]],
// [[9, 10], [11, 12, 13]]]
}
-----
http://ideone.com/mAHZyO
May 08 2015
On 05/08/2015 08:05 AM, Dennis Ritchie wrote:why static int idx variable declared within a function deepDup takes the values 1, 1, 1, 2, 2, 3, 4, as opposed to a global variable static int idx, which receives the expected value of 1, 2, 3, 4, 5, 6, 7 ?That's because every template instance is a different type (or implementation). Just like the static variables of foo and bar are separate below, so are the static variables of t!int and t!float: void foo() { static int i; } void bar() { static int i; } void t(T)() { static int i; } Ali
May 08 2015
"Dennis Ritchie" <dennis.ritchie mail.ru> On Friday, 8 May 2015 at 15:13:14 UTC, Ali Çehreli wrote:On 05/08/2015 08:05 AM, Dennis Ritchie wrote:Thankы. Now everything is clear.why static int idx variable declared within a function deepDup takes the values 1, 1, 1, 2, 2, 3, 4, asopposed to aglobal variable static int idx, which receives the expectedvalue of 1,2, 3, 4, 5, 6, 7 ?That's because every template instance is a different type (or implementation). Just like the static variables of foo and bar are separate below, so are the static variables of t!int and t!float: void foo() { static int i; } void bar() { static int i; } void t(T)() { static int i; } Ali
May 08 2015
On Friday, 8 May 2015 at 06:30:46 UTC, Ali Çehreli wrote:On 05/07/2015 07:39 PM, Dennis Ritchie wrote:Nice one. I have the same problem in one of my modules. I might use the above code henceforth.On Friday, 8 May 2015 at 02:23:23 UTC, E.S. Quinn wrote:In D, everything is possible and very easy. :p I called it deepDup: import std.stdio; import std.traits; import std.range; import std.algorithm; auto deepDup(A)(A arr) if (isArray!A) { static if (isArray!(ElementType!A)) { return arr.map!(a => a.deepDup).array; } else { return arr.dup; } } void main() { auto c = [[[1, 2, 3], [4, 5, 6, 7, 8]], [[9, 10], [11, 12, 13]]]; auto d = c.deepDup; d[0][1][1 .. $ - 1] *= 3; writeln("c = ", c); // [[[1, 2, 3], [4, 5, 6, 7, 8]], // [[9, 10], [11, 12, 13]]] // OK writeln("d = ", d); // [[[1, 2, 3], [4, 15, 18, 21, 8]], // [[9, 10], [11, 12, 13]]] // OK } AliIt's because arrays are references types, and .dup is a strictly shallow copy, so you're getting two outer arrays that reference the same set of inner arrays. You'll have to duplicated each of the inner arrays yourself if you need to make a deep copy.Thank you. It really works :) ----- import std.stdio; void main() { auto c = [[[1, 2, 3], [4, 5, 6, 7, 8]], [[9, 10], [11, 12, 13]]]; auto d = [[c[0][0].dup, c[0][1].dup], [c[1][0].dup, c[1][1].dup]]; d[0][1][1 .. $ - 1] *= 3; writeln("c = ", c); // [[[1, 2, 3], [4, 5, 6, 7, 8]], // [[9, 10], [11, 12, 13]]] // OK writeln("d = ", d); // [[[1, 2, 3], [4, 15, 18, 21, 8]], // [[9, 10], [11, 12, 13]]] // OK } ----- http://ideone.com/kJVUhd Maybe there is a way to create .globalDup for multidimensional arrays?
May 08 2015