diff --git a/src/formatting.rs b/src/formatting.rs
index 9c494c3..b439616 100644
--- a/src/formatting.rs
+++ b/src/formatting.rs
@@ -79,7 +79,7 @@ pub fn get_significant_digits(n: &Float) -> usize {
 
 #[cfg(test)]
 fn eval(s: &str) -> Float {
-    Nodes::from_str(s).unwrap().evaluate()
+    crate::nodes::eval(s).unwrap()
 }
 
 #[test]
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..71e5c48
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,4 @@
+pub mod formatting;
+pub mod nodes;
+
+pub use nodes::eval;
diff --git a/src/nodes/mod.rs b/src/nodes/mod.rs
index f46ad3b..1f8f81b 100644
--- a/src/nodes/mod.rs
+++ b/src/nodes/mod.rs
@@ -5,10 +5,16 @@
 use rug::Float;
 
 mod evaluate;
-mod from_str;
+pub mod from_str;
 #[cfg(test)]
 mod tests;
 
+/// helper function to parse to Nodes and immediately evaluate
+pub fn eval(s: &str) -> Result<rug::Float, from_str::Error> {
+    use std::str::FromStr;
+    Nodes::from_str(s).map(|nodes| nodes.evaluate())
+}
+
 pub const PREC: u32 = 512;
 
 #[derive(Debug, Default, Clone, PartialEq)]