Hello,

This will be trivial question but I cannot figure out
what's wrong. I want to convert string to an array of ubyte.

import std.conv;
void main() {
        auto s = "hello";
        ubyte[] b = to!(ubyte[])(s);
}

It compiles but cause run time error:

std.conv.ConvException@C:\APP\D\dmd2\windows\bin\..\..\src\phobos\std\conv.d(3530): Can't parse string: "[" is missing

I cannot understand the meaning of this message.
Replacing s with s.dup to remove immutable doesn't help.
Do I need to use cast?

Regards,
Aki

On Saturday, 11 November 2017 at 15:38:18 UTC, aki wrote:
> Hello,
>
> This will be trivial question but I cannot figure out
> what's wrong. I want to convert string to an array of ubyte.
>
> import std.conv;
> void main() {
>         auto s = "hello";
>         ubyte[] b = to!(ubyte[])(s);
> }
>
> It compiles but cause run time error:
>
> std.conv.ConvException@C:\APP\D\dmd2\windows\bin\..\..\src\phobos\std\conv.d(3530): Can't parse string: "[" is missing
>
> I cannot understand the meaning of this message.
> Replacing s with s.dup to remove immutable doesn't help.
> Do I need to use cast?
>
> Regards,
> Aki

to!(ubyte[]) is a semantic transformation that tries to parse an array literal it seems.

You can use slice casting instead:

     import std.conv;
     void main() {
          auto s = "hello";
          ubyte[] b = cast(ubyte[])(s.dup);
     }

On Saturday, 11 November 2017 at 15:38:18 UTC, aki wrote:
> Hello,
>
> This will be trivial question but I cannot figure out
> what's wrong. I want to convert string to an array of ubyte.
>
> import std.conv;
> void main() {
>         auto s = "hello";
>         ubyte[] b = to!(ubyte[])(s);
> }
>
> It compiles but cause run time error:
>
> std.conv.ConvException@C:\APP\D\dmd2\windows\bin\..\..\src\phobos\std\conv.d(3530): Can't parse string: "[" is missing
>
> I cannot understand the meaning of this message.
> Replacing s with s.dup to remove immutable doesn't help.
> Do I need to use cast?
>
> Regards,
> Aki

I don't know about the error you're seeing, but the generic way to get an array of the underlying data type of a string is via std.string.representation.

import std.string;
auto s = "hello";
auto bytes = s.representation;

https://dlang.org/phobos/std_string.html#.representation

You can also simply cast to the appropriate type if you already know what type of string you have.

auto bytes = cast(immutable(ubyte)[])s;

Of course, if you need a mutable array you should dup:

auto bytes = cast(ubyte[])s.dup;

On Saturday, 11 November 2017 at 15:48:59 UTC, Mike Parker wrote:
> On Saturday, 11 November 2017 at 15:38:18 UTC, aki wrote:
> auto bytes = cast(immutable(ubyte)[])s;
>
> Of course, if you need a mutable array you should dup:
>
> auto bytes = cast(ubyte[])s.dup;

Not only "should" but he "must" otherwise with string literals he'll get a violation access error.

On Saturday, 11 November 2017 at 15:48:59 UTC, Mike Parker wrote:
> On Saturday, 11 November 2017 at 15:38:18 UTC, aki wrote:
>> [...]
>
> I don't know about the error you're seeing, but the generic way to get an array of the underlying data type of a string is via std.string.representation.
>
> import std.string;
> auto s = "hello";
> auto bytes = s.representation;
>
> https://dlang.org/phobos/std_string.html#.representation
>
> You can also simply cast to the appropriate type if you already know what type of string you have.
>
> auto bytes = cast(immutable(ubyte)[])s;
>
> Of course, if you need a mutable array you should dup:
>
> auto bytes = cast(ubyte[])s.dup;

That function needs to be highlighted more through documentation. I've always implemented my own versions to achieve the same as representation. I had no idea that function existed.

If just I knew.

On Saturday, 11 November 2017 at 15:48:59 UTC, Mike Parker wrote:
> auto s = "hello";
> auto bytes = s.representation;
>
> https://dlang.org/phobos/std_string.html#.representation

Thank you for the replay.
Now I know.

aki