diff --git a/src/main.rs b/src/main.rs
index 61535c1..b63f99b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -7,6 +7,7 @@ use clap::Parser;
 mod ast;
 mod builtin;
 mod parser;
+mod span;
 mod table;
 mod value;
 
diff --git a/src/span.rs b/src/span.rs
new file mode 100644
index 0000000..8df7bf0
--- /dev/null
+++ b/src/span.rs
@@ -0,0 +1,66 @@
+use std::fmt;
+use std::ops::Range;
+
+#[derive(Clone, Copy)]
+pub struct Span {
+    start: usize,
+    end: usize,
+}
+
+impl Span {
+    pub fn new(start: usize, end: usize) -> Self {
+        assert!(start <= end, "start must be less than or equal to end");
+        Self { start, end }
+    }
+
+    pub fn range(self) -> Range<usize> {
+        self.start..self.end
+    }
+
+    pub fn join(self, other: Self) -> Self {
+        let start = self.start.min(other.start);
+        let end = self.end.max(other.end);
+        Self::new(start, end)
+    }
+}
+
+impl fmt::Debug for Span {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.range().fmt(f)
+    }
+}
+
+impl From<Span> for Range<usize> {
+    fn from(span: Span) -> Self {
+        span.range()
+    }
+}
+
+pub trait HasSpan {
+    fn span(&self) -> Span;
+}
+
+impl<T> HasSpan for (T, Span) {
+    fn span(&self) -> Span {
+        self.1
+    }
+}
+
+impl chumsky::Span for Span {
+    type Context = ();
+    type Offset = usize;
+
+    fn new(_: Self::Context, range: Range<Self::Offset>) -> Self {
+        Self::new(range.start, range.end)
+    }
+
+    fn context(&self) -> Self::Context {}
+
+    fn start(&self) -> Self::Offset {
+        self.start
+    }
+
+    fn end(&self) -> Self::Offset {
+        self.end
+    }
+}