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digitalmars.D.learn - Why .dup not work with multidimensional arrays?

reply "Dennis Ritchie" <dennis.ritchie mail.ru> writes:
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
parent reply "E.S. Quinn" <anonymous example.com> writes:
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
parent reply "Dennis Ritchie" <dennis.ritchie mail.ru> writes:
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
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 05/07/2015 07:39 PM, Dennis Ritchie wrote:
 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?
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
May 07 2015
next sibling parent reply "Dennis Ritchie" <dennis.ritchie mail.ru> writes:
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
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
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
parent "Dennis Ritchie" <dennis.ritchie mail.ru> writes:
On Friday, 8 May 2015 at 15:13:14 UTC, Ali Çehreli wrote:
 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
Thankы. Now everything is clear.
May 08 2015
prev sibling parent "Chris" <wendlec tcd.ie> writes:
On Friday, 8 May 2015 at 06:30:46 UTC, Ali Çehreli wrote:
 On 05/07/2015 07:39 PM, Dennis Ritchie wrote:
 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?
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
Nice one. I have the same problem in one of my modules. I might use the above code henceforth.
May 08 2015