Re: how to make a simple generic function... parameterized by collection & value

Hi Daniel,

I tried what you suggested but got the same errors.

template<typename T>
struct identity { typedef T type; };
template<typename T>
using NonDeduced = typename identity<T>::type;

template<typename T>
using Validator = std::function<T(const std::string)>;

template<typename C>
Validator<typename C::value_type>
makeSetValidator(const C &validItems,
     NonDeduced<typename C::value_type(*)(const std::string)> validate)
{
     return [=](const std::string s)->typename C::value_type{
         const auto x = validate(s);
         if (std::find(std::begin(validItems), std::end(validItems), x)
             != std::end(validItems))
             return x;
         throw ValueError("Invalid item '" + s + "'");
     };
}

template<typename T>
T validate(const std::string s) { ... }

At the call site I tried:

auto v = makeSetValidator<int>(std::set<int>{-4, 8, 31},
validate<int>);
auto v = makeSetValidator(std::set<int>{-4, 8, 31}, validate<int>);
auto v = makeSetValidator<int>(std::set<int>{-4, 8, 31}, validate);
auto v = makeSetValidator(std::set<int>{-4, 8, 31}, validate);

None of which would compile.

I think I'll give up now:-)

Thanks!

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