The ABC's of Templates in D

[Martin Tschierschke]

On Friday, 31 July 2020 at 17:57:58 UTC, H. S. Teoh wrote:

I choosed the following way regarding:
> 2) The regex is not initialized by ctRegex in order to avoid the
>   compile-time overhead; instead, it's initialized at program 
> startup
>   time.

version(DigitalMars){
    auto reg(alias var)(){
                 return(regex(var));
                 pragma(msg,"regex used");
    }
}

version(LDC){
// reg!() is an alias method, which can check which kind of 
parameter it got
   auto reg(alias var)(){
        static if (__traits(compiles, {enum ctfeFmt = var;}) ){
                 // "Promotion" to compile time value
                 enum ctfeReg =  var ;
                 pragma(msg, "ctRegex used");
                 return(ctRegex!ctfeReg);

        }else{
                 return(regex(var));
                 pragma(msg,"regex used");
                 }
        }
}

So when compiling with DMD my reg!("....") expression is using 
the runtime version.
When compiling with LDC (for release) I use the ctRegex version, 
if possible.
The (alias var) combined with the check if the var is known at 
compile time:
__traits(compiles, {enum ctfeFmt = var;}

I have to admit that the idea was mine, but the crafting only 
with the help of forum members!

// Function to mark all ocurences of the word offshore within 
html bold.
string markoffshore(string to_mark){
    return   
to_mark.replaceAll(reg!(r"([oO]ffshore)"),"<b>$1</b>");
}