• Paul (10/10) Jun 07 2014 Dynamic array is really reference. Right? But why modification of
• monarch_dodra (4/14) Jun 07 2014 It's a value type that holds a reference to data. If you modify
• Paul (8/26) Jun 07 2014 Seems that string[] is not real reference as in C++. As I
• Jonathan M Davis via Digitalmars-d-learn (8/18) Jun 07 2014 The first case just slices the array, so it refers to the same data, but...
• Paul (3/30) Jun 07 2014 Oh, thank you!

"Paul" <aquagnu gmail.com> writes:

Dynamic array is really reference. Right? But why modification of 
parameter in this case does not work:

void some_func(string[] s) {
  s ~= "xxx"; s ~= "yyy";
}

but this works:

void some_fun(ref string[] s) {
  s ~= "xxx"; s ~= "yyy";
}

In the 1st case s is reference too, is not it?

"monarch_dodra" <monarchdodra gmail.com> writes:

On Saturday, 7 June 2014 at 20:56:14 UTC, Paul wrote:
 Dynamic array is really reference. Right? But why modification 
 of parameter in this case does not work:

 void some_func(string[] s) {
  s ~= "xxx"; s ~= "yyy";
 }

 but this works:

 void some_fun(ref string[] s) {
  s ~= "xxx"; s ~= "yyy";
 }

 In the 1st case s is reference too, is not it?

It's a value type that holds a reference to data. If you modify 
the *actual* slice, rather than the referenced items, then you 
need to pass by ref.

"Paul" <aquagnu gmail.com> writes:

On Saturday, 7 June 2014 at 21:17:41 UTC, monarch_dodra wrote:
 On Saturday, 7 June 2014 at 20:56:14 UTC, Paul wrote:
 Dynamic array is really reference. Right? But why modification 
 of parameter in this case does not work:

 void some_func(string[] s) {
 s ~= "xxx"; s ~= "yyy";
 }

 but this works:

 void some_fun(ref string[] s) {
 s ~= "xxx"; s ~= "yyy";
 }

 In the 1st case s is reference too, is not it?

 It's a value type that holds a reference to data. If you modify 
 the *actual* slice, rather than the referenced items, then you 
 need to pass by ref.

Seems that string[] is not real reference as in C++. As I 
understand there is only one array of strings. And when I try to 
modify it in function with ref or whithout - array is the same 
and should be modified. Or there is hidden copy of this array? Or 
there is some policy in reference semantic - modifiable dynamic 
array and read only - when it is copying in stack as function 
argument :)

Jonathan M Davis via Digitalmars-d-learn writes:

On Sat, 07 Jun 2014 20:56:13 +0000
Paul via Digitalmars-d-learn <digitalmars-d-learn puremagic.com> wrote:

 Dynamic array is really reference. Right? But why modification of
 parameter in this case does not work:

 void some_func(string[] s) {
   s ~= "xxx"; s ~= "yyy";
 }

 but this works:

 void some_fun(ref string[] s) {
   s ~= "xxx"; s ~= "yyy";
 }

 In the 1st case s is reference too, is not it?

The first case just slices the array, so it refers to the same data, but the
slice itself is a different slice, so if you append to it, it doesn't affect
the original slice, and it could then result in a reallocation so that the two
slices don't even refer to the same data anymore.

You should read this: http://dlang.org/d-array-article.html

- Jonathan M Davis

"Paul" <aquagnu gmail.com> writes:

On Saturday, 7 June 2014 at 21:32:08 UTC, Jonathan M Davis via
Digitalmars-d-learn wrote:
 On Sat, 07 Jun 2014 20:56:13 +0000
 Paul via Digitalmars-d-learn 
 <digitalmars-d-learn puremagic.com> wrote:

 Dynamic array is really reference. Right? But why modification 
 of
 parameter in this case does not work:

 void some_func(string[] s) {
   s ~= "xxx"; s ~= "yyy";
 }

 but this works:

 void some_fun(ref string[] s) {
   s ~= "xxx"; s ~= "yyy";
 }

 In the 1st case s is reference too, is not it?

 The first case just slices the array, so it refers to the same 
 data, but the
 slice itself is a different slice, so if you append to it, it 
 doesn't affect
 the original slice, and it could then result in a reallocation 
 so that the two
 slices don't even refer to the same data anymore.

 You should read this: http://dlang.org/d-array-article.html

 - Jonathan M Davis

Oh, thank you!