diff --git a/aoc_libs/src/range.rs b/aoc_libs/src/range.rs
index cf76382..a503a49 100644
--- a/aoc_libs/src/range.rs
+++ b/aoc_libs/src/range.rs
@@ -1,5 +1,6 @@
-#[derive(Debug, PartialEq, Eq)]
-pub struct InclusiveRange<T>
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+/// range that includes the start, but excludes the end.
+pub struct Range<T>
 where
     T: PartialOrd + Ord + PartialEq + Copy,
 {
@@ -7,7 +8,7 @@ where
     end: T,
 }
 
-impl<T> InclusiveRange<T>
+impl<T> Range<T>
 where
     T: PartialOrd + Ord + PartialEq + Copy,
 {
@@ -18,21 +19,97 @@ where
         }
     }
 
+    /// calcs whether self and other overlap at all. symettric.
     pub fn any_overlap(&self, other: &Self) -> bool {
-        self.start <= other.end && self.end >= other.start
+        self.start < other.end && self.end > other.start
     }
 
-    pub fn calc_overlap(&self, other: &Self) -> Self {
-        let overlap_start = self.start.min(other.start);
-        let overlap_end = self.end.max(other.end);
-        InclusiveRange::new(overlap_start, overlap_end)
+    /// calculates the range that is part of both ranges.
+    /// Returns None if the ranges do not overlap.
+    pub fn calc_intersection(&self, other: &Self) -> Option<Self> {
+        if self.any_overlap(other) {
+            Some(
+                Self::new(
+                    self.start.max(other.start), self.end.min(other.end)
+                )
+            )
+        } else {
+            None
+        }
     }
 
+    ///calcs whether self completely contains other
     pub fn complete_overlap(&self, other: &Self) -> bool {
-        self.calc_overlap(other) == *self || self.calc_overlap(other) == *other
+        self.start <= other.start && self.end >= other.end
     }
 
     pub fn in_range(&self, other: T) -> bool {
-        self.start <= other && other <= self.end
+        self.start <= other && other < self.end
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn calc_intersection() {
+        let a = Range::new(1, 5);
+        let b = Range::new(3, 9);
+        let c = Range::new(4, 6);
+        let d = Range::new(6, 8);
+        let e = Range::new(1, 4);
+        assert_eq!(a.calc_intersection(&b), Some(Range::new(3,5)));
+        assert_eq!(b.calc_intersection(&a), Some(Range::new(3,5)));
+
+        assert_eq!(a.calc_intersection(&d), None);
+        assert_eq!(d.calc_intersection(&a), None);
+
+        assert_eq!(c.calc_intersection(&b), Some(c));
+        assert_eq!(b.calc_intersection(&c), Some(c));
+
+        assert_eq!(e.calc_intersection(&b), Some(Range::new(3,4)));
+        assert_eq!(b.calc_intersection(&e), Some(Range::new(3,4)));
+    }
+
+    #[test]
+    fn test_any_overlap() {
+        let a = Range::new(1, 5);
+        let b = Range::new(3, 9);
+        let c = Range::new(4, 6);
+        let d = Range::new(6, 8);
+        let e = Range::new(1, 4);
+        assert!(a.any_overlap(&b));
+        assert!(b.any_overlap(&a));
+
+        assert!(b.any_overlap(&c));
+        assert!(c.any_overlap(&b));
+
+        assert!(!d.any_overlap(&a));
+        assert!(!a.any_overlap(&d));
+
+        assert!(e.any_overlap(&b));
+        assert!(b.any_overlap(&e));
+
+        assert!(!e.any_overlap(&d));
+        assert!(!d.any_overlap(&e));
+    }
+    #[test]
+    fn test_complete_overlap() {
+        let a = Range::new(1, 5);
+        let b = Range::new(3, 9);
+        let c = Range::new(4, 6);
+        let d = Range::new(6, 8);
+        let e = Range::new(1, 4);
+        assert!(a.complete_overlap(&a));
+
+        assert!(a.complete_overlap(&e));
+        assert!(!e.complete_overlap(&a));
+
+        assert!(b.complete_overlap(&c));
+        assert!(!c.complete_overlap(&b));
+
+        assert!(b.complete_overlap(&d));
+        assert!(!d.complete_overlap(&b));
     }
 }