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digitalmars.D.learn - How can convert the folowing to D.

reply learner <learner learner.com> writes:
Hi,

I have the following code in C++.

rectangles.erase(rectangles.begin() + index);

where rectangles is:
std::vector<Rectangle> rectangles;

how can I do something similar in D.

Learner.
Mar 31 2016
next sibling parent reply =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
On 03/31/2016 05:34 PM, learner wrote:

 Hi,

 I have the following code in C++.

 rectangles.erase(rectangles.begin() + index);

 where rectangles is:
 std::vector<Rectangle> rectangles;

 how can I do something similar in D.

 Learner.


import std.stdio;

void main() {
     int[] a = [ 1, 2, 3, 4, 5 ];
     writefln("Before: %s", a);
     size_t index = 2;
     a = a[index .. $];       // <-- HERE
     writefln("After : %s", a);
}

Note that it's a cheap operation; the elements are still in memory and 
not destroyed. If you want to run their destructors you can call 
destroy() explicitly:

import std.stdio;
import std.algorithm;
import std.range;

struct Rect {
     int i;

     ~this() {
         writefln("Destroying %s", i);
     }
}

void main() {
     Rect[] a = iota(5).map!(i => Rect(i)).array;

     writefln("Before: %s", a);

     size_t index = 2;

     // If you need to run the destructors now:
     a[0 .. index].each!((ref e) => e.destroy);

     a = a[index .. $];

     writefln("After : %s", a);
}

Prints

Destroying 0
Destroying 1
Destroying 2
Destroying 3
Destroying 4
Before: [Rect(0), Rect(1), Rect(2), Rect(3), Rect(4)]
Destroying 0
Destroying 1
After : [Rect(2), Rect(3), Rect(4)]

Ali
Mar 31 2016
parent learner <learner learner.com> writes:
On Friday, 1 April 2016 at 01:09:32 UTC, Ali Çehreli wrote:

 On 03/31/2016 05:34 PM, learner wrote:

 Hi,

 I have the following code in C++.

 rectangles.erase(rectangles.begin() + index);

 where rectangles is:
 std::vector<Rectangle> rectangles;

 how can I do something similar in D.

 Learner.


 import std.stdio;

 void main() {
     int[] a = [ 1, 2, 3, 4, 5 ];
     writefln("Before: %s", a);
     size_t index = 2;
     a = a[index .. $];       // <-- HERE
     writefln("After : %s", a);
 }

 Note that it's a cheap operation; the elements are still in 
 memory and not destroyed. If you want to run their destructors 
 you can call destroy() explicitly:

 import std.stdio;
 import std.algorithm;
 import std.range;

 struct Rect {
     int i;

     ~this() {
         writefln("Destroying %s", i);
     }
 }

 void main() {
     Rect[] a = iota(5).map!(i => Rect(i)).array;

     writefln("Before: %s", a);

     size_t index = 2;

     // If you need to run the destructors now:
     a[0 .. index].each!((ref e) => e.destroy);

     a = a[index .. $];

     writefln("After : %s", a);
 }

 Prints

 Destroying 0
 Destroying 1
 Destroying 2
 Destroying 3
 Destroying 4
 Before: [Rect(0), Rect(1), Rect(2), Rect(3), Rect(4)]
 Destroying 0
 Destroying 1
 After : [Rect(2), Rect(3), Rect(4)]

 Ali


thanks
Apr 01 2016
prev sibling parent ZombineDev <petar.p.kirov gmail.com> writes:
On Friday, 1 April 2016 at 00:34:49 UTC, learner wrote:

 Hi,

 I have the following code in C++.

 rectangles.erase(rectangles.begin() + index);

 where rectangles is:
 std::vector<Rectangle> rectangles;

 how can I do something similar in D.

 Learner.


Also, if you are using std.container.array (which similar to 
std::vector in C++), you can use its linearRemove method, by 
giving it a range to remove (a slice of itself), like this:

import std.container.array;
import std.range : iota, drop, take;
import std.stdio : writeln;

void main()
{
	auto arr = Array!int(10.iota);	// initialize with [0, 10)

	arr[].writeln();

         // same as arr.linearRemove(arr[5 .. 7]);
	arr.linearRemove(arr[].drop(5).take(2));
	
	arr[].writeln();	
}

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
[0, 1, 2, 3, 4, 7, 8, 9]

The arr[] syntax is just a shorthand of arr.opSlice() which 
returns a range iterating over the elements of the array. Given 
this range, you can use the algorithms from 
http://dlang.org/phobos/std_range to perform further 
manipulations.
Apr 01 2016