Revamped to use `Cons` as a function and `Pair` as its result

* this is analogous to _Scheme_ where a pair (dot-expression) is returned from a call to `cons`
* `Head` and `Tail` are kept as direct references to the `CAR` and `CDR` values of a pair to match e.g. the math operators

1 files changed, 26 insertions, 0 deletions

diff --git a/src/pair.h b/src/pair.h
new file mode 100644
index 0000000..20bef4e
--- /dev/null
+++ b/src/pair.h
@@ -0,0 +1,26 @@
+#ifndef TYPEASVALUE_SRC_PAIR_H_
+#define TYPEASVALUE_SRC_PAIR_H_
+
+#include <type_traits>
+
+namespace tav {
+
+namespace detail { struct pair_tag { }; }
+
+template <
+	typename CAR,
+	typename CDR
+>
+struct Pair : detail::pair_tag {
+	typedef CAR car;
+	typedef CDR cdr;
+
+	typedef Pair<CAR, CDR> type;
+};
+
+template <typename Type>
+using IsPair = std::is_base_of<detail::pair_tag, Type>;
+
+}
+
+#endif  // TYPEASVALUE_SRC_PAIR_H_