diff --git a/src/lib.rs b/src/lib.rs
index 46aa805..d083f0b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -9,6 +9,7 @@ pub enum Needed {
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub enum KError<'a> {
     Incomplete(Needed),
+    EmptyIterator,
     Encoding { expected: &'static str },
     MissingInstanceValue,
     MissingRoot,
@@ -274,6 +275,30 @@ impl<'a> KStream for BytesReader<'a> {
     }
 }
 
+macro_rules! kf_max {
+    ($i: ident, $t: ty) => (
+        pub fn $i<'a>(first: Option<&'a $t>, second: &'a $t) -> Option<&'a $t> {
+            if second.is_nan() { first }
+            else if first.is_none() { Some(second) }
+            else { if first.unwrap() < second { Some(second) } else { first } }
+        }
+    )
+}
+kf_max!(kf32_max, f32);
+kf_max!(kf64_max, f64);
+
+macro_rules! kf_min {
+    ($i: ident, $t: ty) => (
+        pub fn $i<'a>(first: Option<&'a $t>, second: &'a $t) -> Option<&'a $t> {
+            if second.is_nan() { first }
+            else if first.is_none() { Some(second) }
+            else { if first.unwrap() < second { first } else { Some(second) } }
+        }
+    )
+}
+kf_min!(kf32_min, f32);
+kf_min!(kf64_min, f64);
+
 #[cfg(test)]
 mod tests {
     use super::*;