Re: Template variable not reach at compile

[Mike Parker via Digitalmars-d-learn]

On Saturday, 21 July 2018 at 12:17:54 UTC, Greatsam4sure wrote:
Sorry for the typo.  This is the problem
auto arithmetic(T, V, U)(T a,  V b,  U op){
   return mixin("a"~op~"b");
}

//call like this
arithmetic(1.5,2.5,"+");


Compiler says the variable op is not reach at compile time.  So 
how can the varible a and b be reach at compile time and op is 
not reach. I will appreciate any help. I have also use a static 
if but the same complain.  Just a newbie in D

You aren't using a or b at compile time -- you're using the 
string literals "a" and "b", which have nothing at all to do with 
a and b. In order to get what you want, you need to make op a 
template parameter like this:

auto arithmetic(string op, T, V)(T a, V b)
{
    mixin("a"~op~"b");
}

arithmetic!("+")(1.5, 2.5);