diff --git a/src/api.rs b/src/api.rs
index 40eef3c3..90a918c7 100644
--- a/src/api.rs
+++ b/src/api.rs
@@ -956,7 +956,11 @@ impl Engine {
         ast: AST,
         optimization_level: OptimizationLevel,
     ) -> AST {
-        let fn_lib = ast.1.iter().map(|fn_def| fn_def.as_ref().clone()).collect();
+        let fn_lib = ast
+            .1
+            .iter()
+            .map(|(_, fn_def)| fn_def.as_ref().clone())
+            .collect();
         optimize_into_ast(self, scope, ast.0, fn_lib, optimization_level)
     }
 
diff --git a/src/engine.rs b/src/engine.rs
index 2e1462d9..b0b44a38 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -11,7 +11,6 @@ use crate::token::Position;
 use crate::stdlib::{
     any::TypeId,
     boxed::Box,
-    cmp::Ordering,
     collections::{hash_map::DefaultHasher, HashMap},
     format,
     hash::{Hash, Hasher},
@@ -125,48 +124,41 @@ impl<'a> From<&'a mut Dynamic> for Target<'a> {
 /// So instead this is implemented as a sorted list and binary searched.
 #[derive(Debug, Clone)]
 pub struct FunctionsLib(
-    #[cfg(feature = "sync")] Vec<Arc<FnDef>>,
-    #[cfg(not(feature = "sync"))] Vec<Rc<FnDef>>,
+    #[cfg(feature = "sync")] HashMap<u64, Arc<FnDef>>,
+    #[cfg(not(feature = "sync"))] HashMap<u64, Rc<FnDef>>,
 );
 
-impl FnDef {
-    /// Function to order two FnDef records, for binary search.
-    pub fn compare(&self, name: &str, params_len: usize) -> Ordering {
-        // First order by name
-        match self.name.as_str().cmp(name) {
-            // Then by number of parameters
-            Ordering::Equal => self.params.len().cmp(&params_len),
-            order => order,
-        }
-    }
-}
-
 impl FunctionsLib {
     /// Create a new `FunctionsLib`.
     pub fn new() -> Self {
-        FunctionsLib(Vec::new())
+        FunctionsLib(HashMap::new())
     }
     /// Create a new `FunctionsLib` from a collection of `FnDef`.
     pub fn from_vec(vec: Vec<FnDef>) -> Self {
-        #[cfg(feature = "sync")]
-        {
-            FunctionsLib(vec.into_iter().map(Arc::new).collect())
-        }
-        #[cfg(not(feature = "sync"))]
-        {
-            FunctionsLib(vec.into_iter().map(Rc::new).collect())
-        }
+        FunctionsLib(
+            vec.into_iter()
+                .map(|f| {
+                    let hash = calc_fn_def(&f.name, f.params.len());
+
+                    #[cfg(feature = "sync")]
+                    {
+                        (hash, Arc::new(f))
+                    }
+                    #[cfg(not(feature = "sync"))]
+                    {
+                        (hash, Rc::new(f))
+                    }
+                })
+                .collect(),
+        )
     }
     /// Does a certain function exist in the `FunctionsLib`?
     pub fn has_function(&self, name: &str, params: usize) -> bool {
-        self.0.binary_search_by(|f| f.compare(name, params)).is_ok()
+        self.contains_key(&calc_fn_def(name, params))
     }
     /// Get a function definition from the `FunctionsLib`.
     pub fn get_function(&self, name: &str, params: usize) -> Option<&FnDef> {
-        self.0
-            .binary_search_by(|f| f.compare(name, params))
-            .ok()
-            .map(|n| self.0[n].as_ref())
+        self.get(&calc_fn_def(name, params)).map(|f| f.as_ref())
     }
     /// Merge another `FunctionsLib` into this `FunctionsLib`.
     pub fn merge(&self, other: &Self) -> Self {
@@ -177,16 +169,8 @@ impl FunctionsLib {
         } else {
             let mut functions = self.clone();
 
-            other.iter().cloned().for_each(|fn_def| {
-                if let Some((n, _)) = functions
-                    .iter()
-                    .enumerate()
-                    .find(|(_, f)| f.name == fn_def.name && f.params.len() == fn_def.params.len())
-                {
-                    functions[n] = fn_def;
-                } else {
-                    functions.push(fn_def);
-                }
+            other.iter().for_each(|(hash, fn_def)| {
+                functions.insert(*hash, fn_def.clone());
             });
 
             functions
@@ -196,9 +180,9 @@ impl FunctionsLib {
 
 impl Deref for FunctionsLib {
     #[cfg(feature = "sync")]
-    type Target = Vec<Arc<FnDef>>;
+    type Target = HashMap<u64, Arc<FnDef>>;
     #[cfg(not(feature = "sync"))]
-    type Target = Vec<Rc<FnDef>>;
+    type Target = HashMap<u64, Rc<FnDef>>;
 
     fn deref(&self) -> &Self::Target {
         &self.0
@@ -207,11 +191,11 @@ impl Deref for FunctionsLib {
 
 impl DerefMut for FunctionsLib {
     #[cfg(feature = "sync")]
-    fn deref_mut(&mut self) -> &mut Vec<Arc<FnDef>> {
+    fn deref_mut(&mut self) -> &mut HashMap<u64, Arc<FnDef>> {
         &mut self.0
     }
     #[cfg(not(feature = "sync"))]
-    fn deref_mut(&mut self) -> &mut Vec<Rc<FnDef>> {
+    fn deref_mut(&mut self) -> &mut HashMap<u64, Rc<FnDef>> {
         &mut self.0
     }
 }
@@ -349,6 +333,13 @@ pub(crate) fn calc_fn_spec(fn_name: &str, params: impl Iterator<Item = TypeId>)
     s.finish()
 }
 
+pub(crate) fn calc_fn_def(fn_name: &str, params: usize) -> u64 {
+    let mut s = DefaultHasher::new();
+    fn_name.hash(&mut s);
+    params.hash(&mut s);
+    s.finish()
+}
+
 impl Engine {
     /// Create a new `Engine`
     pub fn new() -> Self {
diff --git a/src/parser.rs b/src/parser.rs
index c8331d35..fe7b3191 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -1,7 +1,7 @@
 //! Main module defining the lexer and parser.
 
 use crate::any::{Dynamic, Union};
-use crate::engine::{Engine, FunctionsLib};
+use crate::engine::{calc_fn_def, Engine, FunctionsLib};
 use crate::error::{LexError, ParseError, ParseErrorType};
 use crate::optimize::{optimize_into_ast, OptimizationLevel};
 use crate::scope::{EntryType as ScopeEntryType, Scope};
@@ -1787,9 +1787,9 @@ pub fn parse_global_expr<'a>(
 /// Parse the global level statements.
 fn parse_global_level<'a>(
     input: &mut Peekable<TokenIterator<'a>>,
-) -> Result<(Vec<Stmt>, Vec<FnDef>), ParseError> {
+) -> Result<(Vec<Stmt>, HashMap<u64, FnDef>), ParseError> {
     let mut statements = Vec::<Stmt>::new();
-    let mut functions = Vec::<FnDef>::new();
+    let mut functions = HashMap::<u64, FnDef>::new();
 
     while input.peek().is_some() {
         // Collect all the function definitions
@@ -1797,13 +1797,7 @@ fn parse_global_level<'a>(
         {
             if matches!(input.peek().expect("should not be None"), (Token::Fn, _)) {
                 let f = parse_fn(input, true)?;
-
-                // Ensure list is sorted
-                match functions.binary_search_by(|fn_def| fn_def.compare(&f.name, f.params.len())) {
-                    Ok(n) => functions[n] = f,        // Override previous definition
-                    Err(n) => functions.insert(n, f), // New function definition
-                }
-
+                functions.insert(calc_fn_def(&f.name, f.params.len()), f);
                 continue;
             }
         }
@@ -1849,9 +1843,10 @@ pub fn parse<'a>(
 ) -> Result<AST, ParseError> {
     let (statements, functions) = parse_global_level(input)?;
 
+    let fn_lib = functions.into_iter().map(|(_, v)| v).collect();
     Ok(
         // Optimize AST
-        optimize_into_ast(engine, scope, statements, functions, optimization_level),
+        optimize_into_ast(engine, scope, statements, fn_lib, optimization_level),
     )
 }
 
diff --git a/src/scope.rs b/src/scope.rs
index 3da54404..a9fd579c 100644
--- a/src/scope.rs
+++ b/src/scope.rs
@@ -397,13 +397,6 @@ impl<'a> Scope<'a> {
         &mut entry.value
     }
 
-    /// Get a mutable reference to an entry in the Scope and downcast it to a specific type
-    pub(crate) fn get_mut_by_type<T: Variant + Clone>(&mut self, key: EntryRef) -> &mut T {
-        self.get_mut(key)
-            .downcast_mut::<T>()
-            .expect("wrong type cast")
-    }
-
     /// Get an iterator to entries in the Scope.
     pub fn iter(&self) -> impl Iterator<Item = &Entry> {
         self.0.iter().rev() // Always search a Scope in reverse order