diff --git a/src/main.rs b/src/main.rs
index a29c779..107dbf5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,9 +1,16 @@
 use std::{
     env,
     io::{self, Read},
+    str::FromStr,
 };
 
-mod parse;
+use rug::Float;
+
+mod nodes;
+
+pub fn parse_and_calc(s: &str) -> Float {
+    nodes::Nodes::from_str(s).unwrap().evaluate()
+}
 
 fn main() {
     let input = match env::args().nth(1) {
@@ -14,5 +21,6 @@ fn main() {
             buf
         }
     };
-    println!("{:.3}", parse::parse(&input));
+
+    println!("{:.3}", parse_and_calc(&input));
 }
diff --git a/src/nodes/evaluate.rs b/src/nodes/evaluate.rs
new file mode 100644
index 0000000..ae78ed1
--- /dev/null
+++ b/src/nodes/evaluate.rs
@@ -0,0 +1,148 @@
+use rug::{
+    Float,
+    ops::{AddFrom, DivFrom, MulFrom, PowFrom, SubFrom},
+};
+
+use crate::nodes::{Function, Node, Nodes, Operator};
+
+impl Nodes {
+    /// Consume the `Nodes`, collapsing them down to a single number
+    pub fn evaluate(mut self) -> Float {
+        let nodes = &mut self.0;
+
+        while let Some(end) = nodes.iter().position(|n| *n == Node::ParenthesisEnd) {
+            collapse_toplevel(nodes, end);
+        }
+        let len = nodes.len();
+        collapse_toplevel(nodes, len);
+
+        match nodes.pop().unwrap() {
+            Node::Number(n) => n,
+            _ => panic!("failed to collapse nodes: {nodes:?}"),
+        }
+    }
+}
+
+fn collapse_toplevel(nodes: &mut Vec<Node>, mut end: usize) {
+    let start = nodes[0..end]
+        .iter()
+        .rposition(|n| *n == Node::ParenthesisStart)
+        .unwrap_or(0);
+
+    while let Some((index, variant)) = nodes[start..end]
+        .iter()
+        .filter_map(|n| match n {
+            Node::Function(f) => Some(f),
+            _ => None,
+        })
+        .cloned()
+        .enumerate()
+        .next()
+    {
+        match &mut nodes[start..end][index + 1] {
+            Node::Number(n) => match variant {
+                Function::Sine => n.sin_mut(),
+                Function::Cosine => n.cos_mut(),
+            },
+            _ => panic!("function is missing an argument"),
+        };
+
+        nodes.remove(start + index);
+        end -= 1;
+    }
+
+    while let Some(operator) = nodes[start..end]
+        .iter()
+        .position(|n| *n == Node::Operator(Operator::Exp))
+    {
+        let lhs = match nodes.remove(start + operator - 1) {
+            Node::Number(n) => n,
+            n => panic!("operator has an invalid operand: {n:?}"),
+        };
+        end -= 1;
+        match &mut nodes[start..end][operator] {
+            Node::Number(n) => n.pow_from(lhs),
+            n => panic!("operator has an invalid operand: {n:?}"),
+        };
+
+        nodes.remove(start + operator - 1);
+        end -= 1;
+    }
+
+    while let Some(operator) = nodes[start..end]
+        .iter()
+        .position(|n| *n == Node::Operator(Operator::Div))
+    {
+        let lhs = match nodes.remove(start + operator - 1) {
+            Node::Number(n) => n,
+            n => panic!("operator has an invalid operand: {n:?}"),
+        };
+        end -= 1;
+        match &mut nodes[start..end][operator] {
+            Node::Number(n) => n.div_from(lhs),
+            n => panic!("operator has an invalid operand: {n:?}"),
+        };
+
+        nodes.remove(start + operator - 1);
+        end -= 1;
+    }
+
+    while let Some(operator) = nodes[start..end]
+        .iter()
+        .position(|n| *n == Node::Operator(Operator::Mult))
+    {
+        let lhs = match nodes.remove(start + operator - 1) {
+            Node::Number(n) => n,
+            n => panic!("operator has an invalid operand: {n:?}"),
+        };
+        end -= 1;
+        match &mut nodes[start..end][operator] {
+            Node::Number(n) => n.mul_from(lhs),
+            n => panic!("operator has an invalid operand: {n:?}"),
+        };
+
+        nodes.remove(start + operator - 1);
+        end -= 1;
+    }
+
+    while let Some(operator) = nodes[start..end]
+        .iter()
+        .position(|n| *n == Node::Operator(Operator::Plus))
+    {
+        let lhs = match nodes.remove(start + operator - 1) {
+            Node::Number(n) => n,
+            n => panic!("operator has an invalid operand: {n:?}"),
+        };
+        end -= 1;
+        match &mut nodes[start..end][operator] {
+            Node::Number(n) => n.add_from(lhs),
+            n => panic!("operator has an invalid operand: {n:?}"),
+        };
+
+        nodes.remove(start + operator - 1);
+        end -= 1;
+    }
+
+    while let Some(operator) = nodes[start..end]
+        .iter()
+        .position(|n| *n == Node::Operator(Operator::Minus))
+    {
+        let lhs = match nodes.remove(start + operator - 1) {
+            Node::Number(n) => n,
+            n => panic!("operator has an invalid operand: {n:?}"),
+        };
+        end -= 1;
+        match &mut nodes[start..end][operator] {
+            Node::Number(n) => n.sub_from(lhs),
+            n => panic!("operator has an invalid operand: {n:?}"),
+        };
+
+        nodes.remove(start + operator - 1);
+        end -= 1;
+    }
+
+    if nodes.len() > 1 {
+        nodes.remove(end);
+        nodes.remove(start);
+    }
+}
diff --git a/src/nodes/from_str.rs b/src/nodes/from_str.rs
new file mode 100644
index 0000000..95f25a7
--- /dev/null
+++ b/src/nodes/from_str.rs
@@ -0,0 +1,110 @@
+use std::str::FromStr;
+
+use rug::{Float, float::ParseFloatError, ops::CompleteRound};
+
+use crate::nodes::{Node, Nodes, PREC};
+
+#[derive(Clone, Debug, thiserror::Error)]
+pub enum Error {
+    #[error("invalid function: {0}")]
+    InvalidFunction(String),
+    #[error("invalid operator: {0}")]
+    InvalidOperator(char),
+    #[error("failed to parse number '{0}': {1}")]
+    NumberParsing(String, ParseFloatError),
+}
+
+#[derive(Clone, Debug, Default)]
+enum ParsingState {
+    #[default]
+    Start,
+    ReadingFunctionName(usize),
+    ReadingNumber(usize),
+}
+
+impl FromStr for Nodes {
+    type Err = Error;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut nodes = Vec::new();
+        let mut state = ParsingState::default();
+
+        let is_ignored_char = |c: &char| !matches!(c, ' ' | '&' | '\n');
+
+        let filtered_string: String = s.chars().filter(is_ignored_char).collect();
+
+        for (i, c) in filtered_string.char_indices() {
+            let mut start = false;
+            match state {
+                ParsingState::Start => start = true,
+                ParsingState::ReadingFunctionName(start_index) => {
+                    if !c.is_alphabetic() {
+                        nodes.push(Node::Function(
+                            filtered_string[start_index..i].parse().map_err(|()| {
+                                Error::InvalidFunction(filtered_string[start_index..i].to_owned())
+                            })?,
+                        ));
+
+                        state = ParsingState::Start;
+                        start = true;
+                    }
+                }
+                ParsingState::ReadingNumber(start_index) => {
+                    if !c.is_numeric() {
+                        nodes.push(Node::Number(
+                            Float::parse_radix(&filtered_string[start_index..i], 10)
+                                .map_err(|e| {
+                                    Error::NumberParsing(
+                                        filtered_string[start_index..i].to_owned(),
+                                        e,
+                                    )
+                                })?
+                                .complete(PREC),
+                        ));
+
+                        state = ParsingState::Start;
+                        start = true;
+                    }
+                }
+            }
+
+            if start {
+                if c.is_alphabetic() {
+                    state = ParsingState::ReadingFunctionName(i);
+                } else if c.is_numeric() {
+                    state = ParsingState::ReadingNumber(i);
+                } else if c == '(' {
+                    nodes.push(Node::ParenthesisStart);
+                } else if c == ')' {
+                    nodes.push(Node::ParenthesisEnd);
+                } else {
+                    nodes.push(Node::Operator(
+                        c.try_into().map_err(|()| Error::InvalidOperator(c))?,
+                    ));
+                }
+            }
+        }
+
+        let i = filtered_string.len();
+        match state {
+            ParsingState::Start => {}
+            ParsingState::ReadingFunctionName(start_index) => {
+                nodes.push(Node::Function(
+                    filtered_string[start_index..i].parse().map_err(|()| {
+                        Error::InvalidFunction(filtered_string[start_index..i].to_owned())
+                    })?,
+                ));
+            }
+            ParsingState::ReadingNumber(start_index) => {
+                nodes.push(Node::Number(
+                    Float::parse_radix(&filtered_string[start_index..i], 10)
+                        .map_err(|e| {
+                            Error::NumberParsing(filtered_string[start_index..i].to_owned(), e)
+                        })?
+                        .complete(PREC),
+                ));
+            }
+        }
+
+        Ok(Nodes(nodes))
+    }
+}
diff --git a/src/nodes/mod.rs b/src/nodes/mod.rs
new file mode 100644
index 0000000..874c98b
--- /dev/null
+++ b/src/nodes/mod.rs
@@ -0,0 +1,69 @@
+//! This module contains the intermediate representation (IR) used by this crate,
+//! as well as the logic to parse it from a string (`Node::from_str`),
+//! and the logic to evaluate it into a single number (`Node::evaluate`).
+
+use std::str::FromStr;
+
+use rug::Float;
+
+mod evaluate;
+mod from_str;
+#[cfg(test)]
+mod tests;
+
+pub const PREC: u32 = 512;
+
+#[derive(Default, Debug, Clone, PartialEq)]
+pub struct Nodes(Vec<Node>);
+impl AsRef<[Node]> for Nodes {
+    fn as_ref(&self) -> &[Node] {
+        self.0.as_ref()
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+enum Node {
+    Function(Function),
+    ParenthesisStart,
+    ParenthesisEnd,
+    Number(Float),
+    Operator(Operator),
+}
+
+#[derive(Clone, Debug, PartialEq)]
+enum Operator {
+    Plus,
+    Minus,
+    Mult,
+    Div,
+    Exp,
+}
+impl TryFrom<char> for Operator {
+    type Error = ();
+    fn try_from(value: char) -> Result<Self, Self::Error> {
+        match value {
+            '+' => Ok(Self::Plus),
+            '-' => Ok(Self::Minus),
+            '*' => Ok(Self::Mult),
+            '/' => Ok(Self::Div),
+            '^' => Ok(Self::Exp),
+            _ => Err(()),
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+enum Function {
+    Sine,
+    Cosine,
+}
+impl FromStr for Function {
+    type Err = ();
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "sin" => Ok(Self::Sine),
+            "cos" => Ok(Self::Cosine),
+            _ => Err(()),
+        }
+    }
+}
diff --git a/src/nodes/tests.rs b/src/nodes/tests.rs
new file mode 100644
index 0000000..022f343
--- /dev/null
+++ b/src/nodes/tests.rs
@@ -0,0 +1,37 @@
+use std::str::FromStr;
+
+use rug::Float;
+
+use crate::nodes::{Function, Node, Nodes, Operator, PREC};
+
+#[test]
+fn test_nodes_to_num() {
+    assert_eq!(
+        Nodes(vec![
+            Node::Function(Function::Sine),
+            Node::ParenthesisStart,
+            Node::Number(Float::with_val(PREC, 2)),
+            Node::ParenthesisEnd,
+            Node::Operator(Operator::Plus),
+            Node::Number(Float::with_val(PREC, 1))
+        ])
+        .evaluate()
+        .to_f64_round(rug::float::Round::Nearest),
+        1.9092974268256817,
+    );
+}
+
+#[test]
+fn test_nodes_from_str() {
+    assert_eq!(
+        Nodes::from_str("sin(2) + 1").unwrap().as_ref(),
+        &[
+            Node::Function(Function::Sine),
+            Node::ParenthesisStart,
+            Node::Number(Float::with_val(PREC, 2)),
+            Node::ParenthesisEnd,
+            Node::Operator(Operator::Plus),
+            Node::Number(Float::with_val(PREC, 1))
+        ],
+    )
+}
diff --git a/src/parse.rs b/src/parse.rs
deleted file mode 100644
index 7141938..0000000
--- a/src/parse.rs
+++ /dev/null
@@ -1,327 +0,0 @@
-use std::str::FromStr;
-
-use rug::{
-    Float,
-    float::ParseFloatError,
-    ops::{AddFrom, CompleteRound, DivFrom, MulFrom, PowFrom, SubFrom},
-};
-
-#[derive(Clone, Debug, thiserror::Error)]
-enum Error {
-    #[error("invalid function: {0}")]
-    InvalidFunction(String),
-    #[error("invalid operator: {0}")]
-    InvalidOperator(char),
-    #[error("failed to parse number '{0}': {1}")]
-    NumberParsing(String, ParseFloatError),
-}
-
-const PREC: u32 = 512;
-
-#[derive(Clone, Debug, PartialEq)]
-enum Node {
-    Function(Function),
-    ParenthesisStart,
-    ParenthesisEnd,
-    Number(Float),
-    Operator(Operator),
-}
-
-#[derive(Clone, Debug, PartialEq)]
-enum Operator {
-    Plus,
-    Minus,
-    Mult,
-    Div,
-    Exp,
-}
-impl TryFrom<char> for Operator {
-    type Error = ();
-    fn try_from(value: char) -> Result<Self, Self::Error> {
-        match value {
-            '+' => Ok(Self::Plus),
-            '-' => Ok(Self::Minus),
-            '*' => Ok(Self::Mult),
-            '/' => Ok(Self::Div),
-            '^' => Ok(Self::Exp),
-            _ => Err(()),
-        }
-    }
-}
-
-#[derive(Clone, Debug, PartialEq)]
-enum Function {
-    Sine,
-    Cosine,
-}
-impl FromStr for Function {
-    type Err = ();
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        match s {
-            "sin" => Ok(Self::Sine),
-            "cos" => Ok(Self::Cosine),
-            _ => Err(()),
-        }
-    }
-}
-
-#[derive(Clone, Debug, Default)]
-enum ParsingState {
-    #[default]
-    Start,
-    ReadingFunctionName(usize),
-    ReadingNumber(usize),
-}
-
-fn nodes_from_str(s: &str) -> Result<Vec<Node>, Error> {
-    let mut nodes = Vec::new();
-    let mut state = ParsingState::default();
-
-    let is_ignored_char = |c: &char| !matches!(c, ' ' | '&' | '\n');
-
-    let filtered_string: String = s.chars().filter(is_ignored_char).collect();
-
-    for (i, c) in filtered_string.char_indices() {
-        let mut start = false;
-        match state {
-            ParsingState::Start => start = true,
-            ParsingState::ReadingFunctionName(start_index) => {
-                if !c.is_alphabetic() {
-                    nodes.push(Node::Function(
-                        filtered_string[start_index..i].parse().map_err(|()| {
-                            Error::InvalidFunction(filtered_string[start_index..i].to_owned())
-                        })?,
-                    ));
-
-                    state = ParsingState::Start;
-                    start = true;
-                }
-            }
-            ParsingState::ReadingNumber(start_index) => {
-                if !c.is_numeric() {
-                    nodes.push(Node::Number(
-                        Float::parse_radix(&filtered_string[start_index..i], 10)
-                            .map_err(|e| {
-                                Error::NumberParsing(filtered_string[start_index..i].to_owned(), e)
-                            })?
-                            .complete(PREC),
-                    ));
-
-                    state = ParsingState::Start;
-                    start = true;
-                }
-            }
-        }
-
-        if start {
-            if c.is_alphabetic() {
-                state = ParsingState::ReadingFunctionName(i);
-            } else if c.is_numeric() {
-                state = ParsingState::ReadingNumber(i);
-            } else if c == '(' {
-                nodes.push(Node::ParenthesisStart);
-            } else if c == ')' {
-                nodes.push(Node::ParenthesisEnd);
-            } else {
-                nodes.push(Node::Operator(
-                    c.try_into().map_err(|()| Error::InvalidOperator(c))?,
-                ));
-            }
-        }
-    }
-
-    let i = filtered_string.len();
-    match state {
-        ParsingState::Start => {}
-        ParsingState::ReadingFunctionName(start_index) => {
-            nodes.push(Node::Function(
-                filtered_string[start_index..i].parse().map_err(|()| {
-                    Error::InvalidFunction(filtered_string[start_index..i].to_owned())
-                })?,
-            ));
-        }
-        ParsingState::ReadingNumber(start_index) => {
-            nodes.push(Node::Number(
-                Float::parse_radix(&filtered_string[start_index..i], 10)
-                    .map_err(|e| {
-                        Error::NumberParsing(filtered_string[start_index..i].to_owned(), e)
-                    })?
-                    .complete(PREC),
-            ));
-        }
-    }
-
-    Ok(nodes)
-}
-
-fn collapse_toplevel(nodes: &mut Vec<Node>, mut end: usize) {
-    let start = nodes[0..end]
-        .iter()
-        .rposition(|n| *n == Node::ParenthesisStart)
-        .unwrap_or(0);
-
-    while let Some((index, variant)) = nodes[start..end]
-        .iter()
-        .filter_map(|n| match n {
-            Node::Function(f) => Some(f),
-            _ => None,
-        })
-        .cloned()
-        .enumerate()
-        .next()
-    {
-        match &mut nodes[start..end][index + 1] {
-            Node::Number(n) => match variant {
-                Function::Sine => n.sin_mut(),
-                Function::Cosine => n.cos_mut(),
-            },
-            _ => panic!("function is missing an argument"),
-        };
-
-        nodes.remove(start + index);
-        end -= 1;
-    }
-
-    while let Some(operator) = nodes[start..end]
-        .iter()
-        .position(|n| *n == Node::Operator(Operator::Exp))
-    {
-        let lhs = match nodes.remove(start + operator - 1) {
-            Node::Number(n) => n,
-            n => panic!("operator has an invalid operand: {n:?}"),
-        };
-        end -= 1;
-        match &mut nodes[start..end][operator] {
-            Node::Number(n) => n.pow_from(lhs),
-            n => panic!("operator has an invalid operand: {n:?}"),
-        };
-
-        nodes.remove(start + operator - 1);
-        end -= 1;
-    }
-
-    while let Some(operator) = nodes[start..end]
-        .iter()
-        .position(|n| *n == Node::Operator(Operator::Div))
-    {
-        let lhs = match nodes.remove(start + operator - 1) {
-            Node::Number(n) => n,
-            n => panic!("operator has an invalid operand: {n:?}"),
-        };
-        end -= 1;
-        match &mut nodes[start..end][operator] {
-            Node::Number(n) => n.div_from(lhs),
-            n => panic!("operator has an invalid operand: {n:?}"),
-        };
-
-        nodes.remove(start + operator - 1);
-        end -= 1;
-    }
-
-    while let Some(operator) = nodes[start..end]
-        .iter()
-        .position(|n| *n == Node::Operator(Operator::Mult))
-    {
-        let lhs = match nodes.remove(start + operator - 1) {
-            Node::Number(n) => n,
-            n => panic!("operator has an invalid operand: {n:?}"),
-        };
-        end -= 1;
-        match &mut nodes[start..end][operator] {
-            Node::Number(n) => n.mul_from(lhs),
-            n => panic!("operator has an invalid operand: {n:?}"),
-        };
-
-        nodes.remove(start + operator - 1);
-        end -= 1;
-    }
-
-    while let Some(operator) = nodes[start..end]
-        .iter()
-        .position(|n| *n == Node::Operator(Operator::Plus))
-    {
-        let lhs = match nodes.remove(start + operator - 1) {
-            Node::Number(n) => n,
-            n => panic!("operator has an invalid operand: {n:?}"),
-        };
-        end -= 1;
-        match &mut nodes[start..end][operator] {
-            Node::Number(n) => n.add_from(lhs),
-            n => panic!("operator has an invalid operand: {n:?}"),
-        };
-
-        nodes.remove(start + operator - 1);
-        end -= 1;
-    }
-
-    while let Some(operator) = nodes[start..end]
-        .iter()
-        .position(|n| *n == Node::Operator(Operator::Minus))
-    {
-        let lhs = match nodes.remove(start + operator - 1) {
-            Node::Number(n) => n,
-            n => panic!("operator has an invalid operand: {n:?}"),
-        };
-        end -= 1;
-        match &mut nodes[start..end][operator] {
-            Node::Number(n) => n.sub_from(lhs),
-            n => panic!("operator has an invalid operand: {n:?}"),
-        };
-
-        nodes.remove(start + operator - 1);
-        end -= 1;
-    }
-
-    if nodes.len() > 1 {
-        nodes.remove(end);
-        nodes.remove(start);
-    }
-}
-
-fn nodes_to_num(mut nodes: Vec<Node>) -> Float {
-    while let Some(end) = nodes.iter().position(|n| *n == Node::ParenthesisEnd) {
-        collapse_toplevel(&mut nodes, end);
-    }
-    let len = nodes.len();
-    collapse_toplevel(&mut nodes, len);
-
-    match nodes.pop().unwrap() {
-        Node::Number(n) => n,
-        _ => panic!("failed to collapse nodes: {nodes:?}"),
-    }
-}
-
-pub fn parse(s: &str) -> Float {
-    nodes_to_num(nodes_from_str(s).unwrap())
-}
-
-#[test]
-fn test_nodes_to_num() {
-    assert_eq!(
-        nodes_to_num(vec![
-            Node::Function(Function::Sine),
-            Node::ParenthesisStart,
-            Node::Number(Float::with_val(PREC, 2)),
-            Node::ParenthesisEnd,
-            Node::Operator(Operator::Plus),
-            Node::Number(Float::with_val(PREC, 1))
-        ])
-        .to_f64_round(rug::float::Round::Nearest),
-        1.9092974268256817,
-    );
-}
-
-#[test]
-fn test_nodes_from_str() {
-    assert_eq!(
-        nodes_from_str("sin(2) + 1").unwrap().as_slice(),
-        &[
-            Node::Function(Function::Sine),
-            Node::ParenthesisStart,
-            Node::Number(Float::with_val(PREC, 2)),
-            Node::ParenthesisEnd,
-            Node::Operator(Operator::Plus),
-            Node::Number(Float::with_val(PREC, 1))
-        ],
-    )
-}