Apply suggestions from code review

Co-authored-by: Raynel Sanchez <87539502+raynelfss@users.noreply.github.com>

Author: gadial

crates/circuit/src/parameter/parameter_expression.rs

@@ -137,6 +137,7 @@ impl ParameterExpression {
         qpy_replay(self, &self.name_map, &mut replay);
         replay
     }
+   #[inline]
     pub fn num_of_symbols(&self) -> usize {
         self.name_map.len()
     }
@@ -265,10 +266,7 @@ impl ParameterExpression {
         subs_operations: Option<Vec<(usize, HashMap<Symbol, ParameterExpression>)>>,
         additional_symbols: Option<&HashSet<Symbol>>,
     ) -> Result<Self, ParameterError> {
-        let mut symbols = match additional_symbols {
-            None => HashSet::new(),
-            Some(symbol_map) => symbol_map.clone(),
-        };
+        let mut symbols = additional_symbols.unwrap_or_default();
         // the stack contains the latest lhs and rhs values
         let mut stack: Vec<ParameterExpression> = Vec::new();
         let subs_operations = subs_operations.unwrap_or_default();

crates/qpy/src/params.rs

@@ -498,7 +498,6 @@ pub(crate) fn unpack_parameter_expression(
             replay.push(OPReplay { op, lhs, rhs });
         };
     }
-    // let additional_symbols = HashSet::new();
     let additional_symbols = HashSet::from_iter(param_uuid_map.values().filter_map(|v| match v {
         GenericValue::ParameterExpressionSymbol(s) => Some(s.clone()),
         _ => None,
@@ -619,7 +618,7 @@ pub(crate) fn unpack_parameter_vector(
 }
 
 // exp should be a symbol (for parameter/parameter vector element)
-// but more than that: it should no contain other symbols in its symbol table
+// but more than that: it should not contain other symbols in its symbol table
 // since if, e.g. exp was `0*x+y` and got simplified to `y` we still need
 // to store `x`, so we must treat exp as an expression
 fn expression_as_single_symbol(exp: &ParameterExpression) -> Option<Symbol> {