diff --git a/include/tcframe/validator/number.hpp b/include/tcframe/validator/number.hpp
new file mode 100644
index 0000000..7c2c7d8
--- /dev/null
+++ b/include/tcframe/validator/number.hpp
@@ -0,0 +1,7 @@
+namespace tcframe {
+
+bool isBetween(long long N, long long mn, long long mx) {
+    return N >= mn && N <= mx;
+}
+
+}