algo/search: improve minimises documentation

algo/search.hpp

@@ -9,6 +9,9 @@
 
 #pragma once
 
+#include "../types/traits.hpp"
+
+#include <iterator>
 #include <functional>
 
 
@@ -23,10 +26,30 @@ namespace cruft::search {
     /// The provided function will be invoked with the supplied argument pack
     /// as the first arguments and the dereferenced iterator as the final
     /// argument.
-    template <typename InputT, typename FunctionT, typename ...Args>
-    InputT
-    minimises (InputT first, InputT last, FunctionT &&func, Args &&...args)
-    {
+    ///
+    /// \tparam ForwardT   A forward iterator
+    /// \tparam FunctionT  An invokable
+    /// \param first  The first iterator in the range to be searched
+    /// \param last   The last iterator in the range to be searched
+    /// \param func   A functional which returns a comparable value
+    /// \param args   The first arguments passed to `func`
+    /// \return  A pair of the best score, and the best iterator
+    template <
+        typename ForwardT,
+        typename FunctionT,
+        typename ...Args
+    >
+    auto
+    minimises (
+        ForwardT first,
+        ForwardT last,
+        FunctionT &&func,
+        Args &&...args
+    ) {
+        using value_type = typename std::iterator_traits<ForwardT>::value_type;
+        using score_t = std::invoke_result_t<FunctionT, Args..., value_type>;
+        static_assert (::cruft::is_orderable_v<score_t>);
+
         auto best_score = std::invoke (func, args..., *first);
         auto best_item = first;