Yes it is. The dup version just make an extra copy of array for no reason. 



po 3. 12. 2018 21:10 odesílatel Goksan via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com> napsal:
Are there any differences between these 2 methods of copying
elements?

double[] array = [ 1, 20, 2, 30, 7, 11 ];

// Non dup
double[6] bracket_syntax_dup = array;
bracket_syntax_dup[] = array;
bracket_syntax_dup[0] = 50;

// Dup
double[6] normal_dup = array.dup;
normal_dup[0] = 100;

OUTPUT: (array, bracket_syntax_dup and normal_dup respectively):
[1, 20, 2, 30, 7, 11]
[50, 20, 2, 30, 7, 11]
[100, 20, 2, 30, 7, 11]