Where does the template parameter E come from?

[David Nadlinger]

On 3/28/11 4:54 PM, simendsjo wrote:
> When running compose with two arguments, the implementation uses the
> template parameter E. I don't understand what's going on here as E isn't
> submitted to the template - what type is E?
> […]
> typeof({ E a; return fun0(fun1(a)); }()) doIt(E)(E a)
> {  […] }

doIt is a function template, so E will be deduced to be whatever type 
the passed argument is – you won't notice the extra »template layer« as 
E is automatically inferred from the argument.

For better understanding, you might want to look at the definition like 
this:

---
template composeImpl(fun...) {
     […]
     template doIt(E) {
         typeof({ E a; return fun0(fun1(a)); }()) doIt(E a) {
             […]
         }
     }
}
---

David