diff --git a/src/parse/formulas.rs b/src/parse/formulas.rs
index f9f30e0..e8803a2 100644
--- a/src/parse/formulas.rs
+++ b/src/parse/formulas.rs
@@ -446,116 +446,6 @@ fn quantified_formula(input: &str, quantifier: Quantifier, level: usize)
 	Ok(formula)
 }
 
-/*struct ComparisonOperatorIterator<'i>
-{
-	original_input: &'i str,
-	input: &'i str,
-}
-
-impl<'i> ComparisonOperatorIterator<'i>
-{
-	pub fn new(input: &'i str) -> Self
-	{
-		Self
-		{
-			original_input: input,
-			input,
-		}
-	}
-}
-
-// TODO: refactor
-impl<'i> std::iter::Iterator for ComparisonOperatorIterator<'i>
-{
-	type Item = Result<(&'i str, &'i str, crate::ComparisonOperator), crate::parse::Error>;
-
-	fn next(&mut self) -> Option<Self::Item>
-	{
-		loop
-		{
-			self.input = self.input.trim_start();
-
-			let first_character = match self.input.chars().next()
-			{
-				None => return None,
-				Some(first_character) => first_character,
-			};
-
-			if self.input.starts_with(")")
-			{
-				return Some(Err(crate::parse::Error::new_unmatched_parenthesis(
-					crate::parse::error::Location::new(0, Some(1)))));
-			}
-
-			match parenthesized_expression(self.input)
-			{
-				Ok(Some((_, remaining_input))) =>
-				{
-					self.input = remaining_input;
-					continue;
-				},
-				Ok(None) => (),
-				Err(error) => return Some(Err(error)),
-			}
-
-			match number(self.input)
-			{
-				Ok(Some((_, remaining_input))) =>
-				{
-					self.input = remaining_input;
-					continue;
-				}
-				Ok(None) => (),
-				Err(error) => return Some(Err(error)),
-			}
-
-			let index_left = self.input.as_ptr() as usize - self.original_input.as_ptr() as usize;
-			let input_left = self.original_input.split_at(index_left).0.trim_end();
-
-			if let Some((symbol, remaining_input)) = symbol(self.input)
-			{
-				self.input = remaining_input;
-
-				match symbol
-				{
-					Symbol::Greater =>
-						return Some(Ok((input_left, remaining_input,
-							crate::ComparisonOperator::Greater))),
-					Symbol::GreaterOrEqual =>
-						return Some(Ok((input_left, remaining_input,
-							crate::ComparisonOperator::GreaterOrEqual))),
-					Symbol::Less =>
-						return Some(Ok((input_left, remaining_input,
-							crate::ComparisonOperator::Less))),
-					Symbol::LessOrEqual =>
-						return Some(Ok((input_left, remaining_input,
-							crate::ComparisonOperator::LessOrEqual))),
-					Symbol::Equal =>
-						return Some(Ok((input_left, remaining_input,
-							crate::ComparisonOperator::Equal))),
-					Symbol::NotEqual =>
-						return Some(Ok((input_left, remaining_input,
-							crate::ComparisonOperator::NotEqual))),
-					_ => continue,
-				}
-			}
-
-			match identifier(self.input)
-			{
-				Some((_, remaining_input)) =>
-				{
-					self.input = remaining_input;
-					continue;
-				}
-				None => (),
-			}
-
-			return Some(Err(crate::parse::Error::new_character_not_allowed(first_character,
-				crate::parse::error::Location::new(0, Some(0)))));
-		}
-	}
-}*/
-
 #[cfg(test)]
 mod tests
 {