How to convert a string type to an array of chars

Question

I'm trying to translate some C code to D, and I've come across this:

char[] welcome = "\t\tWelcome to the strange land of protected mode!\r\n";

It gives this warning:

main.d:5:18: error: cannot implicitly convert expression ("\x09\x09Welcome to the strange land of protected mode!\x0d\x0a") of type string to char[]
    5 | char[] welcome = "\t\tWelcome to the strange land of protected mode!\r\n";
      |                  ^

How do I do this without typing each character out individually in the array?

Answer 1

As already mentioned, strings already are an array of chars. In fact, here is the definition of string:

alias string = immutable(char)[];

(from object.d)

A string thus differs from a char[] only in that the contents of the array is immutable.

• Depending on your goal, you may not need a char[] after all, and string will work as well.
• If you need the array to be writable (i.e. you expect welcome[2] = 'x'; to work), then using .dup will create a copy at runtime.
• Sometimes C function declarations are not properly annotated with const, and will not accept pointers to immutable characters. In this case, using a cast is acceptable.
• I don't think there is a language feature to place a string literal directly in a writable data segment, in the same way that static char[] s = ['a', 'b', 'c']; does, but it's likely doable as a template or CTFE function.

Answer 2

12.16.1 - Strings

1. A string is an array of characters. String literals are just an easy way to write character arrays. String literals are immutable (read only).

   char[] str1 = "abc";                // error, "abc" is not mutable
   char[] str2 = "abc".dup;            // ok, make mutable copy
   immutable(char)[] str3 = "abc";     // ok
   immutable(char)[] str4 = str1;      // error, str4 is not mutable
   immutable(char)[] str5 = str1.idup; // ok, make immutable copy
   

2. The name string is aliased to immutable(char)[], so the above declarations could be equivalently written as:

   char[] str1 = "abc";     // error, "abc" is not mutable
   char[] str2 = "abc".dup; // ok, make mutable copy
   string str3 = "abc";     // ok
   string str4 = str1;      // error, str4 is not mutable
   string str5 = str1.idup; // ok, make immutable copy
   

So:

char[] welcome = "\t\tWelcome to the strange land of protected mode!\r\n".dup;