Add compile time mutable variable type

[Chang Long]

On Tuesday, 5 June 2012 at 05:39:34 UTC, Ali Çehreli wrote:
> On 06/04/2012 06:22 PM, Chang Long wrote:
>
> > The previous two example is not correct, please see this one:
>
> Your post sounds interesting but there are lots of errors:
>
> > size_t line l;  <-- ERROR
>
> > void this(string name) { <-- ERROR
>
> etc. Can you actually compile that code?
>
> It would be better if you can present your question with less 
> code.
>
> Ali
this is what I mean, I can't make it more smaller.
-----------------------------------------------------------
abstract class Template_parameter_Base{
         TypeInto ti;
         string name ;
         this(TypeInto ti, string name) {
             this.ti = ti ;
             this.name = name ;
         }
}
class Template_parameter(T) : Template_parameter_Base {
	T   value ;
  	alias value this;
	void assign(ref T t){
		value = t ;
	}
}
class Template_Engine {
	string name ;
	Template_parameter_Base[string] parameters ;
	void this(string name) {
		this.name = name ;
	}
}
class Template(string name) {
	static compile_time_mutable(Template_Engine)  engine = new 
Template_Engine!name ;
	void assign(string name, T)(ref T t){
		static if(name in vars) {
			static const parameter	= cast(Template_parameter!T) 
engine.parameters[name];
			static assert( parameter.ti == typeid(T) );
		} else {
			static const parameter	=  new Template_parameter!T(typeid(T), 
name) ;
			static engine.parameters[name]		=  parameter ;
		}
		parameter.assign(t);
	}
}
void main(){
	static tpl = new Template!"home_page" ;
	auto  is_login  =  false ;
	tpl.assign!"is_login"( is_login) ) ;
	if( is_login ) {
		tpl.assign!"user"( new User() ) ;
	}
	
	auto string switch_user = "new_user_email" ;
	if( switch_user !is null ) {
		tpl.assign!"user"( new User(switch_user) ) ;
	}
	
	tpl.assign!"user"( true )  ; // static assert error
}
-----------------------------------------------------------

After think what is done,  a better way is put the 
Template_parameter on the annotation data section.

some things like this:
class Template_Engine(string name) {
      static this_ti =  typeid( typeof(this) ) ;
      void assign(string name, T)(ref T t){
             static const parameter = new Template_parameter!(T, 
name) ;
             ti.createAnnotation("Template_Engine_Parameter", 
parameter);
             parameter.assign(t);
       }
       void render(){
            auto parameters =  
this_ti.getParametersByName("Template_Engine_Parameter") ;
            // compile template to dynamic link library by 
template file and parameters
      }
}