Replace auto with explicit type

It seems that the older c++ version was deducing auto as a
initializer_list rather than a size_t

Fixes #161

Author: Robin Miller

source/meta/type_traits.h

@@ -2,7 +2,8 @@
 //  Copyright (C) Michigan State University, 2016-2017.
 //  Released under the MIT Software license; see doc/LICENSE
 //
-//  Extensions on the standard library type traits to handle Empirical classes (such as Ptr).
+//  Extensions on the standard library type traits to handle Empirical classes
+//  (such as Ptr).
 
 #ifndef EMP_TYPE_TRAITS_H
 #define EMP_TYPE_TRAITS_H
@@ -16,37 +17,62 @@
 namespace emp {
 
   // Customized type traits
-  template <typename T> struct is_ptr_type           { enum { value = false }; };
-  template <typename T> struct is_ptr_type<T*>       { enum { value = true }; };
-  template <typename T> struct is_ptr_type<T* const> { enum { value = true }; };
-  template <typename T> struct is_ptr_type<Ptr<T>>   { enum { value = true }; };
   template <typename T>
-  constexpr bool is_ptr_type_v(const T&) { return is_ptr_type<T>::value; }
+  struct is_ptr_type {
+    enum { value = false };
+  };
+  template <typename T>
+  struct is_ptr_type<T *> {
+    enum { value = true };
+  };
+  template <typename T>
+  struct is_ptr_type<T *const> {
+    enum { value = true };
+  };
+  template <typename T>
+  struct is_ptr_type<Ptr<T>> {
+    enum { value = true };
+  };
+  template <typename T>
+  constexpr bool is_ptr_type_v(const T &) {
+    return is_ptr_type<T>::value;
+  }
 
-  template <typename T> struct remove_ptr_type { };    // Not ponter; should break!
-  template <typename T> struct remove_ptr_type<T*>     { using type = T; };
-  template <typename T> struct remove_ptr_type<Ptr<T>> { using type = T; };
+  template <typename T>
+  struct remove_ptr_type {};  // Not ponter; should break!
+  template <typename T>
+  struct remove_ptr_type<T *> {
+    using type = T;
+  };
+  template <typename T>
+  struct remove_ptr_type<Ptr<T>> {
+    using type = T;
+  };
   template <typename T>
   using remove_ptr_type_t = typename remove_ptr_type<T>::type;
   // @CAO: Make sure we are dealing with const and volitile pointers correctly.
 
   // Can we convert the first pointer into the second?
-  template <typename T1, typename T2> struct ptr_pair {
+  template <typename T1, typename T2>
+  struct ptr_pair {
     static constexpr bool Same() { return false; }
     static constexpr bool SameBase() { return false; }
-    static bool ConvertOK(T1 * ptr) { return dynamic_cast<T2*>(ptr); }
+    static bool ConvertOK(T1 *ptr) { return dynamic_cast<T2 *>(ptr); }
   };
-  template <typename T> struct ptr_pair<T,T> {
+  template <typename T>
+  struct ptr_pair<T, T> {
     static constexpr bool Same() { return true; }
     static constexpr bool SameBase() { return true; }
     static constexpr bool ConvertOK(T *) { return true; }
   };
-  template <typename T> struct ptr_pair<T, const T> {
+  template <typename T>
+  struct ptr_pair<T, const T> {
     static constexpr bool Same() { return false; }
     static constexpr bool SameBase() { return true; }
     static constexpr bool ConvertOK(T *) { return true; }
   };
-  template <typename T> struct ptr_pair<const T, T> {
+  template <typename T>
+  struct ptr_pair<const T, T> {
     static constexpr bool Same() { return false; }
     static constexpr bool SameBase() { return true; }
     static constexpr bool ConvertOK(T *) { return false; }
@@ -451,7 +477,7 @@ namespace emp {
 
   template <typename Needle, typename Haystack,
             template <typename, typename> class... Cmp>
-  static constexpr auto variadic_index_of_v{
+  static constexpr size_t variadic_index_of_v{
     variadic_index_of<Needle, Haystack, Cmp...>::value};
 
   namespace __impl_variadics_type_traits {