问题
A template function I have written has the following signature:
template<class IteratorT>
auto average(IteratorT& begin, IteratorT& end) -> decltype(*begin)
I thought that this would work fine, but apparently it doesn't. I call the function by passing in pointers to the beginning and end of an array:
int integers[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8 };
auto average = sigma::average(&integers[0], &integers[8]);
But clang tells me that it cannot find a matching function:
error: no matching function for call to '
average'
What have I done wrong?
回答1:
The problem is that the expression&integers[0] returns an rvalue which cannot be bound to non-const reference parameters of average template function.
So the solution is to make the parameters non-reference (removed &):
template<class IteratorT>
auto average(IteratorT begin, IteratorT end) -> decltype(*begin)
Then call it as (although it is not that important, but &integers[8] seems to invoke undefined behavior, pedantically speaking):
auto average = sigma::average(integers, integers + 8);
But why do you need such a function template to begin with? You could use std::accumulate as:
#include <algorithm> //must include this
auto average = std::accumulate(integers, integers + 8, 0)/8;
来源：https://stackoverflow.com/questions/9351463/no-matching-function-call-to-template-function