Compile time initialization of AA

[Ali Çehreli]

On 03/23/2018 03:43 PM, Xavier Bigand wrote:
 > I am trying to initialize an global immutable associative array of
 > structs, but it doesn't compile.

Current solution is to initialize the AA in a 'static this()' block or 
('shared static this()').

 > I am getting the following error message : "Error: not an associative
 > array initializer".
 >
 > As I really need to store my data for a compile time purpose if we can't
 > do that with AA, I'll use arrays instead.

You can create and use AAs at compile time, which may be an acceptable 
use for your case as well:

struct EntryPoint
{
     string  moduleName;
     string  functionName;
     bool    beforeForwarding = false;
}

EntryPoint[string] makeEntryPoints() {
     EntryPoint[string] entryPoints = [
         "wglDescribePixelFormat": 
EntryPoint("opengl32.forward_initialization", "wglDescribePixelFormat")
     ];
     return entryPoints;
}

string useEntryPoints(EntryPoint[string] aa) {
     return aa["wglDescribePixelFormat"].moduleName;
}

void main() {
     enum s = useEntryPoints(makeEntryPoints());
     static const s2 = s;
}

The computations of 's' and 's2' in main are performed at compile time. 
If you can getaway with that, great. :) Otherwise, you have to 
initialize at runtime in a 'shared static this()' block, which can still 
be 'immutable':

// NOTE the addition of 'pure':
EntryPoint[string] makeEntryPoints() pure {
     // Same as above...
}

immutable EntryPoint[string] entryPoints;
shared static this() {
     // Yes, can initialize immutable:
     entryPoints = makeEntryPoints();
}

Ali