Changed `ListIndex` to return false if no index is found

* analogously to `list-index` and `find` in SRFI-1

1 files changed, 6 insertions, 0 deletions

diff --git a/src/type.h b/src/type.h
index 508e22f..c2ad2d8 100644
--- a/src/type.h
+++ b/src/type.h
@@ -38,6 +38,12 @@ using IsEqualValue = Boolean<X::value == Y::value>;
 template <typename X>
 using IsTrue = IsEqualValue<X, Boolean<true>>;
 
+template <typename X>
+using IsBoolean = Eval<std::is_same<typename X::value_type, bool>>;
+
+template <typename X>
+using IsSize = Eval<std::is_same<typename X::value_type, std::size_t>>;
+
 }
 
 #endif  // TYPEASVALUE_SRC_TYPE_H_