diff --git a/pkg/saccharine/expression.go b/pkg/saccharine/expression.go
deleted file mode 100644
index 3cf127c..0000000
--- a/pkg/saccharine/expression.go
+++ /dev/null
@@ -1,31 +0,0 @@
-package saccharine
-
-type Expression interface {
-	expression()
-}
-
-/** ------------------------------------------------------------------------- */
-
-type Abstraction struct {
-	Parameters []string
-	Body       Expression
-}
-
-type Application struct {
-	Abstraction Expression
-	Arguments   []Expression
-}
-
-type Atom struct {
-	Name string
-}
-
-type Clause struct {
-	Statements []Statement
-	Returns    Expression
-}
-
-func (Abstraction) expression() {}
-func (Application) expression() {}
-func (Atom) expression()        {}
-func (Clause) expression()      {}
diff --git a/pkg/saccharine/parse.go b/pkg/saccharine/parse.go
index 3bb9285..60a8736 100644
--- a/pkg/saccharine/parse.go
+++ b/pkg/saccharine/parse.go
@@ -7,10 +7,10 @@ import (
 	"git.maximhutz.com/max/lambda/pkg/iterator"
 )
 
-type TokenIterator = iterator.Iterator[Token]
+type tokenIterator = iterator.Iterator[Token]
 
-func parseRawToken(i *TokenIterator, expected TokenType) (*Token, error) {
-	return iterator.Do(i, func(i *TokenIterator) (*Token, error) {
+func parseRawToken(i *tokenIterator, expected TokenType) (*Token, error) {
+	return iterator.Do(i, func(i *tokenIterator) (*Token, error) {
 		if tok, err := i.Next(); err != nil {
 			return nil, err
 		} else if tok.Type != expected {
@@ -21,7 +21,7 @@ func parseRawToken(i *TokenIterator, expected TokenType) (*Token, error) {
 	})
 }
 
-func passSoftBreaks(i *TokenIterator) {
+func passSoftBreaks(i *tokenIterator) {
 	for {
 		if _, err := parseRawToken(i, TokenSoftBreak); err != nil {
 			return
@@ -29,8 +29,8 @@ func passSoftBreaks(i *TokenIterator) {
 	}
 }
 
-func parseToken(i *TokenIterator, expected TokenType, ignoreSoftBreaks bool) (*Token, error) {
-	return iterator.Do(i, func(i *TokenIterator) (*Token, error) {
+func parseToken(i *tokenIterator, expected TokenType, ignoreSoftBreaks bool) (*Token, error) {
+	return iterator.Do(i, func(i *tokenIterator) (*Token, error) {
 		if ignoreSoftBreaks {
 			passSoftBreaks(i)
 		}
@@ -39,7 +39,7 @@ func parseToken(i *TokenIterator, expected TokenType, ignoreSoftBreaks bool) (*T
 	})
 }
 
-func parseString(i *TokenIterator) (string, error) {
+func parseString(i *tokenIterator) (string, error) {
 	if tok, err := parseToken(i, TokenAtom, true); err != nil {
 		return "", fmt.Errorf("no variable (col %d): %w", i.Index(), err)
 	} else {
@@ -47,7 +47,7 @@ func parseString(i *TokenIterator) (string, error) {
 	}
 }
 
-func parseBreak(i *TokenIterator) (*Token, error) {
+func parseBreak(i *tokenIterator) (*Token, error) {
 	if tok, softErr := parseRawToken(i, TokenSoftBreak); softErr == nil {
 		return tok, nil
 	} else if tok, hardErr := parseRawToken(i, TokenHardBreak); hardErr == nil {
@@ -57,7 +57,7 @@ func parseBreak(i *TokenIterator) (*Token, error) {
 	}
 }
 
-func parseList[U any](i *TokenIterator, fn func(*TokenIterator) (U, error), minimum int) ([]U, error) {
+func parseList[U any](i *tokenIterator, fn func(*tokenIterator) (U, error), minimum int) ([]U, error) {
 	results := []U{}
 
 	for {
@@ -72,8 +72,8 @@ func parseList[U any](i *TokenIterator, fn func(*TokenIterator) (U, error), mini
 	}
 }
 
-func parseAbstraction(i *TokenIterator) (*Abstraction, error) {
-	return iterator.Do(i, func(i *TokenIterator) (*Abstraction, error) {
+func parseAbstraction(i *tokenIterator) (*Abstraction, error) {
+	return iterator.Do(i, func(i *tokenIterator) (*Abstraction, error) {
 		if _, err := parseToken(i, TokenSlash, true); err != nil {
 			return nil, fmt.Errorf("no function slash (col %d): %w", i.MustGet().Column, err)
 		} else if parameters, err := parseList(i, parseString, 0); err != nil {
@@ -88,8 +88,8 @@ func parseAbstraction(i *TokenIterator) (*Abstraction, error) {
 	})
 }
 
-func parseApplication(i *TokenIterator) (*Application, error) {
-	return iterator.Do(i, func(i *TokenIterator) (*Application, error) {
+func parseApplication(i *tokenIterator) (*Application, error) {
+	return iterator.Do(i, func(i *tokenIterator) (*Application, error) {
 		if _, err := parseToken(i, TokenOpenParen, true); err != nil {
 			return nil, fmt.Errorf("no openning brackets (col %d): %w", i.MustGet().Column, err)
 		} else if expressions, err := parseList(i, parseExpression, 1); err != nil {
@@ -102,7 +102,7 @@ func parseApplication(i *TokenIterator) (*Application, error) {
 	})
 }
 
-func parseAtom(i *TokenIterator) (*Atom, error) {
+func parseAtom(i *tokenIterator) (*Atom, error) {
 	if tok, err := parseToken(i, TokenAtom, true); err != nil {
 		return nil, fmt.Errorf("no variable (col %d): %w", i.Index(), err)
 	} else {
@@ -110,7 +110,7 @@ func parseAtom(i *TokenIterator) (*Atom, error) {
 	}
 }
 
-func parseStatements(i *TokenIterator) ([]Statement, error) {
+func parseStatements(i *tokenIterator) ([]Statement, error) {
 	statements := []Statement{}
 
 	//nolint:errcheck
@@ -129,7 +129,7 @@ func parseStatements(i *TokenIterator) ([]Statement, error) {
 	return statements, nil
 }
 
-func parseClause(i *TokenIterator, braces bool) (*Clause, error) {
+func parseClause(i *tokenIterator, braces bool) (*Clause, error) {
 	if braces {
 		if _, err := parseToken(i, TokenOpenBrace, true); err != nil {
 			return nil, err
@@ -158,8 +158,8 @@ func parseClause(i *TokenIterator, braces bool) (*Clause, error) {
 	return &Clause{Statements: stmts[:len(stmts)-1], Returns: last.Value}, nil
 }
 
-func parseExpression(i *TokenIterator) (Expression, error) {
-	return iterator.Do(i, func(i *TokenIterator) (Expression, error) {
+func parseExpression(i *tokenIterator) (Expression, error) {
+	return iterator.Do(i, func(i *tokenIterator) (Expression, error) {
 		passSoftBreaks(i)
 
 		switch peek := i.MustGet(); peek.Type {
@@ -177,8 +177,8 @@ func parseExpression(i *TokenIterator) (Expression, error) {
 	})
 }
 
-func parseLet(i *TokenIterator) (*LetStatement, error) {
-	return iterator.Do(i, func(i *TokenIterator) (*LetStatement, error) {
+func parseLet(i *tokenIterator) (*LetStatement, error) {
+	return iterator.Do(i, func(i *tokenIterator) (*LetStatement, error) {
 		if parameters, err := parseList(i, parseString, 1); err != nil {
 			return nil, err
 		} else if _, err := parseToken(i, TokenAssign, true); err != nil {
@@ -191,7 +191,7 @@ func parseLet(i *TokenIterator) (*LetStatement, error) {
 	})
 }
 
-func parseDeclare(i *TokenIterator) (*DeclareStatement, error) {
+func parseDeclare(i *tokenIterator) (*DeclareStatement, error) {
 	if value, err := parseExpression(i); err != nil {
 		return nil, err
 	} else {
@@ -199,7 +199,7 @@ func parseDeclare(i *TokenIterator) (*DeclareStatement, error) {
 	}
 }
 
-func parseStatement(i *TokenIterator) (Statement, error) {
+func parseStatement(i *tokenIterator) (Statement, error) {
 	if let, letErr := parseLet(i); letErr == nil {
 		return let, nil
 	} else if declare, declErr := parseDeclare(i); declErr == nil {
diff --git a/pkg/saccharine/saccharine.go b/pkg/saccharine/saccharine.go
new file mode 100644
index 0000000..a4b2d50
--- /dev/null
+++ b/pkg/saccharine/saccharine.go
@@ -0,0 +1,60 @@
+// Package saccharine defines the AST for the Saccharine language, a sugared
+// lambda calculus with let bindings and multi-statement clauses.
+package saccharine
+
+// An Expression is a node in the Saccharine abstract syntax tree.
+// It is a sealed interface; only types in this package may implement it.
+type Expression interface {
+	expression()
+}
+
+// An Abstraction is a lambda expression with zero or more parameters.
+// A zero-parameter abstraction is treated as a thunk.
+type Abstraction struct {
+	Parameters []string
+	Body       Expression
+}
+
+// An Application applies an expression to zero or more arguments.
+type Application struct {
+	Abstraction Expression
+	Arguments   []Expression
+}
+
+// An Atom is a named variable.
+type Atom struct {
+	Name string
+}
+
+// A Clause is a sequence of statements followed by a return expression.
+type Clause struct {
+	Statements []Statement
+	Returns    Expression
+}
+
+func (Abstraction) expression() {}
+func (Application) expression() {}
+func (Atom) expression()        {}
+func (Clause) expression()      {}
+
+// A Statement is a declaration within a Clause.
+// It is a sealed interface; only types in this package may implement it.
+type Statement interface {
+	statement()
+}
+
+// A LetStatement binds a name (with optional parameters) to an expression.
+type LetStatement struct {
+	Name       string
+	Parameters []string
+	Body       Expression
+}
+
+// A DeclareStatement evaluates an expression for its side effects within a
+// clause.
+type DeclareStatement struct {
+	Value Expression
+}
+
+func (LetStatement) statement()     {}
+func (DeclareStatement) statement() {}
diff --git a/pkg/saccharine/statement.go b/pkg/saccharine/statement.go
deleted file mode 100644
index 03e5302..0000000
--- a/pkg/saccharine/statement.go
+++ /dev/null
@@ -1,20 +0,0 @@
-package saccharine
-
-type Statement interface {
-	statement()
-}
-
-/** ------------------------------------------------------------------------- */
-
-type LetStatement struct {
-	Name       string
-	Parameters []string
-	Body       Expression
-}
-
-type DeclareStatement struct {
-	Value Expression
-}
-
-func (LetStatement) statement()     {}
-func (DeclareStatement) statement() {}