diff --git a/src/format.rs b/src/format.rs
index 21a0533..443224a 100644
--- a/src/format.rs
+++ b/src/format.rs
@@ -1,10 +1,11 @@
 struct TermDisplay<'term>
 {
-	parent_precedence: i32,
+	parent_precedence: Option<i32>,
 	term: &'term crate::Term,
 }
 
-fn display_term<'term>(term: &'term crate::Term, parent_precedence: i32) -> TermDisplay<'term>
+fn display_term<'term>(term: &'term crate::Term, parent_precedence: Option<i32>)
+	-> TermDisplay<'term>
 {
 	TermDisplay
 	{
@@ -15,11 +16,11 @@ fn display_term<'term>(term: &'term crate::Term, parent_precedence: i32) -> Term
 
 struct FormulaDisplay<'formula>
 {
-	parent_precedence: i32,
+	parent_precedence: Option<i32>,
 	formula: &'formula crate::Formula,
 }
 
-fn display_formula<'formula>(formula: &'formula crate::Formula, parent_precedence: i32)
+fn display_formula<'formula>(formula: &'formula crate::Formula, parent_precedence: Option<i32>)
 	-> FormulaDisplay<'formula>
 {
 	FormulaDisplay
@@ -112,7 +113,12 @@ impl<'term> std::fmt::Debug for TermDisplay<'term>
 	fn fmt(&self, format: &mut std::fmt::Formatter) -> std::fmt::Result
 	{
 		let precedence = self.term.precedence();
-		let requires_parentheses = precedence > self.parent_precedence;
+		let requires_parentheses = match self.parent_precedence
+		{
+			Some(parent_precedence) => precedence > parent_precedence,
+			None => false,
+		};
+		let precedence = Some(precedence);
 
 		if requires_parentheses
 		{
@@ -144,7 +150,7 @@ impl<'term> std::fmt::Debug for TermDisplay<'term>
 
 					for argument in &function.arguments
 					{
-						write!(format, "{}{:?}", separator, display_term(&argument, 1000))?;
+						write!(format, "{}{:?}", separator, display_term(&argument, None))?;
 
 						separator = ", ";
 					}
@@ -194,7 +200,12 @@ impl<'formula> std::fmt::Debug for FormulaDisplay<'formula>
 	fn fmt(&self, format: &mut std::fmt::Formatter) -> std::fmt::Result
 	{
 		let precedence = self.formula.precedence();
-		let requires_parentheses = precedence > self.parent_precedence;
+		let requires_parentheses = match self.parent_precedence
+		{
+			Some(parent_precedence) => precedence > parent_precedence,
+			None => false,
+		};
+		let precedence = Some(precedence);
 
 		if requires_parentheses
 		{
@@ -269,17 +280,17 @@ impl<'formula> std::fmt::Debug for FormulaDisplay<'formula>
 			crate::Formula::IfAndOnlyIf(crate::IfAndOnlyIf{left, right})
 				=> write!(format, "{:?} <-> {:?}", display_formula(left, precedence), display_formula(right, precedence))?,
 			crate::Formula::Compare(crate::Compare{operator: crate::ComparisonOperator::Less, left, right})
-				=> write!(format, "{:?} < {:?}", display_term(left, 1000), display_term(right, 1000))?,
+				=> write!(format, "{:?} < {:?}", display_term(left, None), display_term(right, None))?,
 			crate::Formula::Compare(crate::Compare{operator: crate::ComparisonOperator::LessOrEqual, left, right})
-				=> write!(format, "{:?} <= {:?}", display_term(left, 1000), display_term(right, 1000))?,
+				=> write!(format, "{:?} <= {:?}", display_term(left, None), display_term(right, None))?,
 			crate::Formula::Compare(crate::Compare{operator: crate::ComparisonOperator::Greater, left, right})
-				=> write!(format, "{:?} > {:?}", display_term(left, 1000), display_term(right, 1000))?,
+				=> write!(format, "{:?} > {:?}", display_term(left, None), display_term(right, None))?,
 			crate::Formula::Compare(crate::Compare{operator: crate::ComparisonOperator::GreaterOrEqual, left, right})
-				=> write!(format, "{:?} >= {:?}", display_term(left, 1000), display_term(right, 1000))?,
+				=> write!(format, "{:?} >= {:?}", display_term(left, None), display_term(right, None))?,
 			crate::Formula::Compare(crate::Compare{operator: crate::ComparisonOperator::Equal, left, right})
-				=> write!(format, "{:?} = {:?}", display_term(left, 1000), display_term(right, 1000))?,
+				=> write!(format, "{:?} = {:?}", display_term(left, None), display_term(right, None))?,
 			crate::Formula::Compare(crate::Compare{operator: crate::ComparisonOperator::NotEqual, left, right})
-				=> write!(format, "{:?} != {:?}", display_term(left, 1000), display_term(right, 1000))?,
+				=> write!(format, "{:?} != {:?}", display_term(left, None), display_term(right, None))?,
 			crate::Formula::Boolean(true) => write!(format, "#true")?,
 			crate::Formula::Boolean(false) => write!(format, "#false")?,
 			crate::Formula::Predicate(predicate) =>
@@ -294,7 +305,7 @@ impl<'formula> std::fmt::Debug for FormulaDisplay<'formula>
 
 					for argument in &predicate.arguments
 					{
-						write!(format, "{}{:?}", separator, display_term(argument, 1000))?;
+						write!(format, "{}{:?}", separator, display_term(argument, None))?;
 
 						separator = ", "
 					}
@@ -325,7 +336,7 @@ impl std::fmt::Debug for crate::Formula
 {
 	fn fmt(&self, format: &mut std::fmt::Formatter) -> std::fmt::Result
 	{
-		write!(format, "{:?}", display_formula(&self, 1000))
+		write!(format, "{:?}", display_formula(&self, None))
 	}
 }
 
@@ -333,7 +344,7 @@ impl std::fmt::Display for crate::Formula
 {
 	fn fmt(&self, format: &mut std::fmt::Formatter) -> std::fmt::Result
 	{
-		write!(format, "{}", display_formula(&self, 1000))
+		write!(format, "{}", display_formula(&self, None))
 	}
 }
 
@@ -341,7 +352,7 @@ impl std::fmt::Debug for crate::Term
 {
 	fn fmt(&self, format: &mut std::fmt::Formatter) -> std::fmt::Result
 	{
-		write!(format, "{:?}", display_term(&self, 1000))
+		write!(format, "{:?}", display_term(&self, None))
 	}
 }
 
@@ -349,6 +360,6 @@ impl std::fmt::Display for crate::Term
 {
 	fn fmt(&self, format: &mut std::fmt::Formatter) -> std::fmt::Result
 	{
-		write!(format, "{}", display_term(&self, 1000))
+		write!(format, "{}", display_term(&self, None))
 	}
 }