Array Slicing

From DocForge

Array Slicing is the ability to copy only parts of an array. Combined with array concatenation it allows the ability to treat arrays nearly as a linked list. Array slicing is easiest shown:

Digital Mars D

version(tango) {
    import tango.stdc.stdio;
} else {
    import std.stdc.stdio;
}
 
int main() {
    int[] arr=[ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ];
 
    int[] brr=arr[0 .. 4 ];
 
    foreach(int i, j; brr)
        printf("brr[%d] = %d\n", i, j);
 
    return 0;
}

Will print out:

brr[0] = 1
brr[1] = 2
brr[2] = 3
brr[3] = 4
brr[4] = 5

In the Digital Mars D language, the .. operators, when inside an array index lookup, specially refer to a selection of the array. Used with array concatenation you can easily cut elements from an array - in place, even!

version(tango) {
    import tango.stdc.stdio;
} else {
    import std.stdc.stdio;
}
 
int main() {
    int[] arr=[ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ];
 
    printf("before cutting element 4\n");
    foreach(int i, j; arr)
        printf("  arr[%d] = %d\n", i, j);
 
    arr=arr[0 .. 3]~arr[5 .. $-1];
 
    printf("\nafter cutting element 4\n");
    foreach(int i, j; arr)
        printf("  arr[%d] = %d\n", i, j);
 
    return 0;
}

This example will output the following:

before cutting element 4
  arr[0] = 1
  arr[1] = 2
  arr[2] = 3
  arr[3] = 4
  arr[4] = 5
  arr[5] = 6
  arr[6] = 7
  arr[7] = 8
  arr[8] = 9
  arr[9] = 10

after cutting element 4
  arr[0] = 1
  arr[1] = 2
  arr[2] = 3
  arr[3] = 4
  arr[4] = 6
  arr[5] = 7
  arr[6] = 8
  arr[7] = 9
  arr[8] = 10