Complete StaticVec implementation.

README.md

@@ -2288,8 +2288,9 @@ engine.set_max_operations(0);               // allow unlimited operations
 ```
 
 The concept of one single _operation_ in Rhai is volatile - it roughly equals one expression node,
-one statement, one iteration of a loop, or one function call etc. with sub-expressions and statement
+loading a variable/constant, one operator call, one complete statement, one iteration of a loop,
-blocks executed inside these contexts accumulated on top.
+or one function call etc. with sub-expressions and statement blocks executed inside these contexts accumulated on top.
+A good rule-of-thumb is that one simple non-trivial expression consumes on average 5-10 operations.
 
 One _operation_ can take an unspecified amount of time and CPU cycles, depending on the particular operation
 involved.  For example, loading a constant consumes very few CPU cycles, while calling an external Rust function,

src/api.rs

@@ -652,7 +652,10 @@ impl Engine {
         let scripts = [script];
         let stream = lex(&scripts);
 
-        parse_global_expr(&mut stream.peekable(), self, scope, self.optimization_level)
+        {
+            let mut peekable = stream.peekable();
+            parse_global_expr(&mut peekable, self, scope, self.optimization_level)
+        }
     }
 
     /// Evaluate a script file.
@@ -748,11 +751,10 @@ impl Engine {
         scope: &mut Scope,
         script: &str,
     ) -> Result<T, Box<EvalAltResult>> {
-        // Since the AST will be thrown away afterwards, don't bother to optimize it
         let ast = self.compile_with_scope_and_optimization_level(
             scope,
             &[script],
-            OptimizationLevel::None,
+            self.optimization_level,
         )?;
         self.eval_ast_with_scope(scope, &ast)
     }

src/engine.rs

@@ -119,11 +119,11 @@ impl Target<'_> {
                     .map_err(|_| EvalAltResult::ErrorCharMismatch(pos))?;
 
                 let mut chars: StaticVec<char> = s.chars().collect();
-                let ch = *chars.get_ref(*index);
+                let ch = chars[*index];
 
                 // See if changed - if so, update the String
                 if ch != new_ch {
-                    *chars.get_mut(*index) = new_ch;
+                    chars[*index] = new_ch;
                     s.clear();
                     chars.iter().for_each(|&ch| s.push(ch));
                 }
@@ -190,7 +190,7 @@ impl<'a> State<'a> {
     }
     /// Get a script-defined function definition from the `State`.
     pub fn get_function(&self, hash: u64) -> Option<&FnDef> {
-        self.fn_lib.get(&hash).map(|f| f.as_ref())
+        self.fn_lib.get(&hash).map(|fn_def| fn_def.as_ref())
     }
 }
 
@@ -463,7 +463,7 @@ fn search_scope<'a>(
                     .downcast_mut::<Module>()
                     .unwrap()
             } else {
-                let (id, root_pos) = modules.get_ref(0);
+                let (id, root_pos) = modules.get(0);
 
                 scope.find_module(id).ok_or_else(|| {
                     Box::new(EvalAltResult::ErrorModuleNotFound(id.into(), *root_pos))
@@ -736,8 +736,6 @@ impl Engine {
         pos: Position,
         level: usize,
     ) -> Result<(Dynamic, State<'s>), Box<EvalAltResult>> {
-        self.inc_operations(&mut state, pos)?;
-
         let orig_scope_level = state.scope_level;
         state.scope_level += 1;
 
@@ -1120,6 +1118,7 @@ impl Engine {
                 let index = if state.always_search { None } else { *index };
                 let mod_and_hash = modules.as_ref().map(|m| (m, *hash_var));
                 let (target, typ) = search_scope(scope, &name, mod_and_hash, index, *pos)?;
+                self.inc_operations(state, *pos)?;
 
                 // Constants cannot be modified
                 match typ {
@@ -1171,6 +1170,8 @@ impl Engine {
         size: usize,
         level: usize,
     ) -> Result<(), Box<EvalAltResult>> {
+        self.inc_operations(state, expr.position())?;
+
         match expr {
             Expr::FnCall(x) if x.1.is_none() => {
                 let arg_values =
@@ -1328,13 +1329,13 @@ impl Engine {
             #[cfg(not(feature = "no_object"))]
             Dynamic(Union::Map(rhs_value)) => match lhs_value {
                 // Only allows String or char
-                Dynamic(Union::Str(s)) => Ok(rhs_value.contains_key(s.as_ref()).into()),
+                Dynamic(Union::Str(s)) => Ok(rhs_value.contains_key(s.as_str()).into()),
                 Dynamic(Union::Char(c)) => Ok(rhs_value.contains_key(&c.to_string()).into()),
                 _ => Err(Box::new(EvalAltResult::ErrorInExpr(lhs.position()))),
             },
             Dynamic(Union::Str(rhs_value)) => match lhs_value {
                 // Only allows String or char
-                Dynamic(Union::Str(s)) => Ok(rhs_value.contains(s.as_ref()).into()),
+                Dynamic(Union::Str(s)) => Ok(rhs_value.contains(s.as_str()).into()),
                 Dynamic(Union::Char(c)) => Ok(rhs_value.contains(c).into()),
                 _ => Err(Box::new(EvalAltResult::ErrorInExpr(lhs.position()))),
             },
@@ -1382,6 +1383,8 @@ impl Engine {
                         let index = if state.always_search { None } else { *index };
                         let mod_and_hash = modules.as_ref().map(|m| (m, *hash_var));
                         let (lhs_ptr, typ) = search_scope(scope, name, mod_and_hash, index, *pos)?;
+                        self.inc_operations(state, *pos)?;
+
                         match typ {
                             ScopeEntryType::Constant => Err(Box::new(
                                 EvalAltResult::ErrorAssignmentToConstant(name.clone(), *pos),
@@ -1465,13 +1468,13 @@ impl Engine {
 
                 let mut args: StaticVec<_> = arg_values.iter_mut().collect();
 
-                if name == KEYWORD_EVAL && args.len() == 1 && args.get_ref(0).is::<String>() {
+                if name == KEYWORD_EVAL && args.len() == 1 && args.get(0).is::<String>() {
                     let hash_fn = calc_fn_hash(empty(), name, once(TypeId::of::<String>()));
 
                     if !self.has_override(state, (hash_fn, *hash_fn_def)) {
                         // eval - only in function call style
                         let prev_len = scope.len();
-                        let pos = args_expr.get_ref(0).position();
+                        let pos = args_expr.get(0).position();
 
                         // Evaluate the text string as a script
                         let result = self.eval_script_expr(scope, state, args.pop(), pos);
@@ -1505,7 +1508,7 @@ impl Engine {
 
                 let mut args: StaticVec<_> = arg_values.iter_mut().collect();
 
-                let (id, root_pos) = modules.get_ref(0); // First module
+                let (id, root_pos) = modules.get(0); // First module
 
                 let module = if let Some(index) = modules.index() {
                     scope
@@ -1663,9 +1666,7 @@ impl Engine {
 
                 match self.eval_expr(scope, state, expr, level)?.as_bool() {
                     Ok(true) => match self.eval_stmt(scope, state, body, level) {
-                        Ok(_) => {
+                        Ok(_) => (),
-                            self.inc_operations(state, body.position())?;
-                        }
                         Err(err) => match *err {
                             EvalAltResult::ErrorLoopBreak(false, _) => (),
                             EvalAltResult::ErrorLoopBreak(true, _) => return Ok(Default::default()),
@@ -1682,9 +1683,7 @@ impl Engine {
             // Loop statement
             Stmt::Loop(body) => loop {
                 match self.eval_stmt(scope, state, body, level) {
-                    Ok(_) => {
+                    Ok(_) => (),
-                        self.inc_operations(state, body.position())?;
-                    }
                     Err(err) => match *err {
                         EvalAltResult::ErrorLoopBreak(false, _) => (),
                         EvalAltResult::ErrorLoopBreak(true, _) => return Ok(Default::default()),
@@ -1773,7 +1772,6 @@ impl Engine {
                 let val = self.eval_expr(scope, state, expr.as_ref().unwrap(), level)?;
                 let var_name = unsafe_cast_var_name_to_lifetime(var_name, &state);
                 scope.push_dynamic_value(var_name, ScopeEntryType::Normal, val, false);
-                self.inc_operations(state, *pos)?;
                 Ok(Default::default())
             }
 
@@ -1781,7 +1779,6 @@ impl Engine {
                 let ((var_name, pos), _) = x.as_ref();
                 let var_name = unsafe_cast_var_name_to_lifetime(var_name, &state);
                 scope.push(var_name, ());
-                self.inc_operations(state, *pos)?;
                 Ok(Default::default())
             }
 
@@ -1791,7 +1788,6 @@ impl Engine {
                 let val = self.eval_expr(scope, state, &expr, level)?;
                 let var_name = unsafe_cast_var_name_to_lifetime(var_name, &state);
                 scope.push_dynamic_value(var_name, ScopeEntryType::Constant, val, true);
-                self.inc_operations(state, *pos)?;
                 Ok(Default::default())
             }
 
@@ -1818,7 +1814,7 @@ impl Engine {
                         .eval_expr(scope, state, &expr, level)?
                         .try_cast::<String>()
                     {
-                        if let Some(resolver) = self.module_resolver.as_ref() {
+                        if let Some(resolver) = &self.module_resolver {
                             // Use an empty scope to create a module
                             let module =
                                 resolver.resolve(self, Scope::new(), &path, expr.position())?;
@@ -1827,7 +1823,6 @@ impl Engine {
                             scope.push_module(mod_name, module);
 
                             state.modules += 1;
-                            self.inc_operations(state, *pos)?;
 
                             Ok(Default::default())
                         } else {
@@ -1884,7 +1879,7 @@ impl Engine {
         }
 
         // Report progress - only in steps
-        if let Some(progress) = self.progress.as_ref() {
+        if let Some(progress) = &self.progress {
             if !progress(state.operations) {
                 // Terminate script if progress returns false
                 return Err(Box::new(EvalAltResult::ErrorTerminated(pos)));

src/module.rs

@@ -51,7 +51,7 @@ pub struct Module {
     all_variables: HashMap<u64, Dynamic>,
 
     /// External Rust functions.
-    functions: HashMap<u64, (String, FnAccess, Vec<TypeId>, SharedNativeFunction)>,
+    functions: HashMap<u64, (String, FnAccess, StaticVec<TypeId>, SharedNativeFunction)>,
 
     /// Flattened collection of all external Rust functions, including those in sub-modules.
     all_functions: HashMap<u64, SharedNativeFunction>,
@@ -292,8 +292,9 @@ impl Module {
         #[cfg(feature = "sync")]
         let func = Arc::new(f);
 
-        self.functions
+        let params = params.into_iter().cloned().collect();
-            .insert(hash_fn, (name, access, params.to_vec(), func));
+
+        self.functions.insert(hash_fn, (name, access, params, func));
 
         hash_fn
     }
@@ -616,13 +617,13 @@ impl Module {
     pub(crate) fn index_all_sub_modules(&mut self) {
         // Collect a particular module.
         fn index_module<'a>(
-            module: &'a mut Module,
+            module: &'a Module,
             qualifiers: &mut Vec<&'a str>,
             variables: &mut Vec<(u64, Dynamic)>,
             functions: &mut Vec<(u64, SharedNativeFunction)>,
             fn_lib: &mut Vec<(u64, SharedFnDef)>,
         ) {
-            for (name, m) in module.modules.iter_mut() {
+            for (name, m) in &module.modules {
                 // Index all the sub-modules first.
                 qualifiers.push(name);
                 index_module(m, qualifiers, variables, functions, fn_lib);
@@ -630,7 +631,7 @@ impl Module {
             }
 
             // Index all variables
-            for (var_name, value) in module.variables.iter() {
+            for (var_name, value) in &module.variables {
                 // Qualifiers + variable name
                 let hash_var = calc_fn_hash(qualifiers.iter().map(|&v| v), var_name, empty());
                 variables.push((hash_var, value.clone()));

src/optimize.rs

@@ -236,24 +236,24 @@ fn optimize_stmt<'a>(stmt: Stmt, state: &mut State<'a>, preserve_result: bool) -
         // import expr as id;
         Stmt::Import(x) => Stmt::Import(Box::new((optimize_expr(x.0, state), x.1))),
         // { block }
-        Stmt::Block(mut x) => {
+        Stmt::Block(x) => {
             let orig_len = x.0.len(); // Original number of statements in the block, for change detection
             let orig_constants_len = state.constants.len(); // Original number of constants in the state, for restore later
             let pos = x.1;
 
             // Optimize each statement in the block
             let mut result: Vec<_> =
-                x.0.iter_mut()
+                x.0.into_iter()
                     .map(|stmt| match stmt {
                         // Add constant into the state
                         Stmt::Const(v) => {
-                            let ((name, pos), expr) = v.as_mut();
+                            let ((name, pos), expr) = *v;
-                            state.push_constant(name, mem::take(expr));
+                            state.push_constant(&name, expr);
                             state.set_dirty();
-                            Stmt::Noop(*pos) // No need to keep constants
+                            Stmt::Noop(pos) // No need to keep constants
                         }
                         // Optimize the statement
-                        _ => optimize_stmt(mem::take(stmt), state, preserve_result),
+                        _ => optimize_stmt(stmt, state, preserve_result),
                     })
                     .collect();
 
@@ -399,14 +399,14 @@ fn optimize_expr<'a>(expr: Expr, state: &mut State<'a>) -> Expr {
         #[cfg(not(feature = "no_object"))]
         Expr::Dot(x) => match (x.0, x.1) {
             // map.string
-            (Expr::Map(mut m), Expr::Property(p)) if m.0.iter().all(|(_, x)| x.is_pure()) => {
+            (Expr::Map(m), Expr::Property(p)) if m.0.iter().all(|(_, x)| x.is_pure()) => {
                 let ((prop, _, _), _) = p.as_ref();
                 // Map literal where everything is pure - promote the indexed item.
                 // All other items can be thrown away.
                 state.set_dirty();
                 let pos = m.1;
-                m.0.iter_mut().find(|((name, _), _)| name == prop)
+                m.0.into_iter().find(|((name, _), _)| name == prop)
-                    .map(|(_, expr)| mem::take(expr).set_position(pos))
+                    .map(|(_, expr)| expr.set_position(pos))
                     .unwrap_or_else(|| Expr::Unit(pos))
             }
             // lhs.rhs
@@ -423,16 +423,16 @@ fn optimize_expr<'a>(expr: Expr, state: &mut State<'a>) -> Expr {
                 // Array literal where everything is pure - promote the indexed item.
                 // All other items can be thrown away.
                 state.set_dirty();
-                a.0.get(i.0 as usize).set_position(a.1)
+                a.0.take(i.0 as usize).set_position(a.1)
             }
             // map[string]
-            (Expr::Map(mut m), Expr::StringConstant(s)) if m.0.iter().all(|(_, x)| x.is_pure()) => {
+            (Expr::Map(m), Expr::StringConstant(s)) if m.0.iter().all(|(_, x)| x.is_pure()) => {
                 // Map literal where everything is pure - promote the indexed item.
                 // All other items can be thrown away.
                 state.set_dirty();
                 let pos = m.1;
-                m.0.iter_mut().find(|((name, _), _)| name == &s.0)
+                m.0.into_iter().find(|((name, _), _)| name == &s.0)
-                    .map(|(_, expr)| mem::take(expr).set_position(pos))
+                    .map(|(_, expr)| expr.set_position(pos))
                     .unwrap_or_else(|| Expr::Unit(pos))
             }
             // string[int]
@@ -446,13 +446,13 @@ fn optimize_expr<'a>(expr: Expr, state: &mut State<'a>) -> Expr {
         },
         // [ items .. ]
         #[cfg(not(feature = "no_index"))]
-        Expr::Array(mut a) => Expr::Array(Box::new((a.0
+        Expr::Array(a) => Expr::Array(Box::new((a.0
-                                .iter_mut().map(|expr| optimize_expr(mem::take(expr), state))
+                                .into_iter().map(|expr| optimize_expr(expr, state))
                                 .collect(), a.1))),
         // [ items .. ]
         #[cfg(not(feature = "no_object"))]
-        Expr::Map(mut m) => Expr::Map(Box::new((m.0
+        Expr::Map(m) => Expr::Map(Box::new((m.0
-                            .iter_mut().map(|((key, pos), expr)| ((mem::take(key), *pos), optimize_expr(mem::take(expr), state)))
+                            .into_iter().map(|((key, pos), expr)| ((key, pos), optimize_expr(expr, state)))
                             .collect(), m.1))),
         // lhs in rhs
         Expr::In(x) => match (x.0, x.1) {
@@ -532,7 +532,7 @@ fn optimize_expr<'a>(expr: Expr, state: &mut State<'a>) -> Expr {
 
         // Do not call some special keywords
         Expr::FnCall(mut x) if DONT_EVAL_KEYWORDS.contains(&(x.0).0.as_ref())=> {
-            x.3 = x.3.iter_mut().map(|a| optimize_expr(mem::take(a), state)).collect();
+            x.3 = x.3.into_iter().map(|a| optimize_expr(a, state)).collect();
             Expr::FnCall(x)
         }
 
@@ -547,12 +547,12 @@ fn optimize_expr<'a>(expr: Expr, state: &mut State<'a>) -> Expr {
             // First search in script-defined functions (can override built-in)
             if state.fn_lib.iter().find(|(id, len)| *id == name && *len == args.len()).is_some() {
                 // A script-defined function overrides the built-in function - do not make the call
-                x.3 = x.3.iter_mut().map(|a| optimize_expr(mem::take(a), state)).collect();
+                x.3 = x.3.into_iter().map(|a| optimize_expr(a, state)).collect();
                 return Expr::FnCall(x);
             }
 
-            let mut arg_values: Vec<_> = args.iter().map(Expr::get_constant_value).collect();
+            let mut arg_values: StaticVec<_> = args.iter().map(Expr::get_constant_value).collect();
-            let mut call_args: Vec<_> = arg_values.iter_mut().collect();
+            let mut call_args: StaticVec<_> = arg_values.iter_mut().collect();
 
             // Save the typename of the first argument if it is `type_of()`
             // This is to avoid `call_args` being passed into the closure
@@ -562,7 +562,7 @@ fn optimize_expr<'a>(expr: Expr, state: &mut State<'a>) -> Expr {
                 ""
             };
 
-            call_fn(&state.engine.packages, &state.engine.global_module, name, &mut call_args, *pos).ok()
+            call_fn(&state.engine.packages, &state.engine.global_module, name, call_args.as_mut(), *pos).ok()
                 .and_then(|result|
                     result.or_else(|| {
                         if !arg_for_type_of.is_empty() {
@@ -579,14 +579,14 @@ fn optimize_expr<'a>(expr: Expr, state: &mut State<'a>) -> Expr {
                     })
                 ).unwrap_or_else(|| {
                     // Optimize function call arguments
-                    x.3 = x.3.iter_mut().map(|a| optimize_expr(mem::take(a), state)).collect();
+                    x.3 = x.3.into_iter().map(|a| optimize_expr(a, state)).collect();
                     Expr::FnCall(x)
                 })
         }
 
         // id(args ..) -> optimize function call arguments
         Expr::FnCall(mut x) => {
-            x.3 = x.3.iter_mut().map(|a| optimize_expr(mem::take(a), state)).collect();
+            x.3 = x.3.into_iter().map(|a| optimize_expr(a, state)).collect();
             Expr::FnCall(x)
         }
 
@@ -702,11 +702,14 @@ pub fn optimize_into_ast(
     const level: OptimizationLevel = OptimizationLevel::None;
 
     #[cfg(not(feature = "no_function"))]
-    let fn_lib: Vec<_> = functions
+    let fn_lib_values: StaticVec<_> = functions
         .iter()
         .map(|fn_def| (fn_def.name.as_str(), fn_def.params.len()))
         .collect();
 
+    #[cfg(not(feature = "no_function"))]
+    let fn_lib = fn_lib_values.as_ref();
+
     #[cfg(feature = "no_function")]
     const fn_lib: &[(&str, usize)] = &[];
 
@@ -716,7 +719,7 @@ pub fn optimize_into_ast(
             let pos = fn_def.body.position();
 
             // Optimize the function body
-            let mut body = optimize(vec![fn_def.body], engine, &Scope::new(), &fn_lib, level);
+            let mut body = optimize(vec![fn_def.body], engine, &Scope::new(), fn_lib, level);
 
             // {} -> Noop
             fn_def.body = match body.pop().unwrap_or_else(|| Stmt::Noop(pos)) {
@@ -742,7 +745,7 @@ pub fn optimize_into_ast(
         match level {
             OptimizationLevel::None => statements,
             OptimizationLevel::Simple | OptimizationLevel::Full => {
-                optimize(statements, engine, &scope, &fn_lib, level)
+                optimize(statements, engine, &scope, fn_lib, level)
             }
         },
         lib,

src/parser.rs

@@ -330,7 +330,7 @@ impl Stmt {
             Stmt::Loop(x) => x.position(),
             Stmt::For(x) => x.2.position(),
             Stmt::Import(x) => (x.1).1,
-            Stmt::Export(x) => (x.get_ref(0).0).1,
+            Stmt::Export(x) => (x.get(0).0).1,
         }
     }
 
@@ -745,7 +745,7 @@ fn parse_call_expr<'a>(
             #[cfg(not(feature = "no_module"))]
             let hash_fn_def = {
                 if let Some(modules) = modules.as_mut() {
-                    modules.set_index(stack.find_module(&modules.get_ref(0).0));
+                    modules.set_index(stack.find_module(&modules.get(0).0));
 
                     // Rust functions are indexed in two steps:
                     // 1) Calculate a hash in a similar manner to script-defined functions,
@@ -786,7 +786,7 @@ fn parse_call_expr<'a>(
                 #[cfg(not(feature = "no_module"))]
                 let hash_fn_def = {
                     if let Some(modules) = modules.as_mut() {
-                        modules.set_index(stack.find_module(&modules.get_ref(0).0));
+                        modules.set_index(stack.find_module(&modules.get(0).0));
 
                         // Rust functions are indexed in two steps:
                         // 1) Calculate a hash in a similar manner to script-defined functions,
@@ -1251,7 +1251,7 @@ fn parse_primary<'a>(
 
             // Qualifiers + variable name
             *hash = calc_fn_hash(modules.iter().map(|(v, _)| v.as_str()), name, empty());
-            modules.set_index(stack.find_module(&modules.get_ref(0).0));
+            modules.set_index(stack.find_module(&modules.get(0).0));
         }
         _ => (),
     }
@@ -1471,7 +1471,7 @@ fn make_dot_expr(
             #[cfg(feature = "no_module")]
             unreachable!();
             #[cfg(not(feature = "no_module"))]
-            return Err(PERR::PropertyExpected.into_err(x.1.unwrap().get_ref(0).1));
+            return Err(PERR::PropertyExpected.into_err(x.1.unwrap().get(0).1));
         }
         // lhs.dot_lhs.dot_rhs
         (lhs, Expr::Dot(x)) => {

src/token.rs

@@ -2,6 +2,7 @@
 
 use crate::error::LexError;
 use crate::parser::INT;
+use crate::utils::StaticVec;
 
 #[cfg(not(feature = "no_float"))]
 use crate::parser::FLOAT;
@@ -425,7 +426,7 @@ pub struct TokenIterator<'a> {
     /// Current position.
     pos: Position,
     /// The input character streams.
-    streams: Vec<Peekable<Chars<'a>>>,
+    streams: StaticVec<Peekable<Chars<'a>>>,
 }
 
 impl<'a> TokenIterator<'a> {

src/unsafe.rs

@@ -61,8 +61,3 @@ pub fn unsafe_cast_var_name_to_lifetime<'s>(name: &str, state: &State) -> Cow<'s
         name.to_string().into()
     }
 }
-
-/// Provide a type instance that is uninitialized.
-pub fn unsafe_uninit<T>() -> T {
-    unsafe { mem::MaybeUninit::uninit().assume_init() }
-}

src/utils.rs

@@ -2,9 +2,7 @@
 //!
 //! # Safety
 //!
-//! The `StaticVec` type has some `unsafe` blocks.
+//! The `StaticVec` type has some `unsafe` blocks to handle conversions between `MaybeUninit` and regular types.
-
-use crate::r#unsafe::unsafe_uninit;
 
 use crate::stdlib::{
     any::TypeId,
@@ -12,7 +10,8 @@ use crate::stdlib::{
     hash::{Hash, Hasher},
     iter::FromIterator,
     mem,
-    ops::Drop,
+    mem::MaybeUninit,
+    ops::{Drop, Index, IndexMut},
     vec::Vec,
 };
 
@@ -52,13 +51,41 @@ pub fn calc_fn_spec<'a>(
     s.finish()
 }
 
-const MAX_STATIC_VEC: usize = 4;
+/// A type to hold a number of values in static storage for no-allocation, quick access.
-
+/// If too many items are stored, it converts into using a `Vec`.
-/// A type to hold a number of values in static storage for speed, and any spill-overs in a `Vec`.
 ///
 /// This is essentially a knock-off of the [`staticvec`](https://crates.io/crates/staticvec) crate.
 /// This simplified implementation here is to avoid pulling in another crate.
 ///
+/// # Implementation
+///
+/// A `StaticVec` holds data in _either one_ of two storages: 1) a fixed-size array of `MAX_STATIC_VEC`
+/// items, and 2) a dynamic `Vec`.  At any time, either one of them (or both) must be empty, depending on the
+/// total number of items.
+///
+/// There is a `len` field containing the total number of items held by the `StaticVec`.
+///
+/// The fixed-size array (`list`) is not initialized (i.e. initialized with `MaybeUninit::uninit()`).
+///
+/// When `len <= MAX_STATIC_VEC`, all elements are stored in the fixed-size array.
+/// Array slots `>= len` are `MaybeUninit::uninit()` while slots `< len` are considered actual data.
+/// In this scenario, the `Vec` (`more`) is empty.
+///
+/// As soon as we try to push a new item into the `StaticVec` that makes the total number exceed
+/// `MAX_STATIC_VEC`, all the items in the fixed-sized array are taken out, replaced with
+/// `MaybeUninit::uninit()` (via `mem::replace`) and pushed into the `Vec`.
+/// Then the new item is added to the `Vec`.
+///
+/// Therefore, if `len > MAX_STATIC_VEC`, then the fixed-size array (`list`) is considered
+/// empty and uninitialized while all data resides in the `Vec` (`more`).
+///
+/// When popping an item off of the `StaticVec`, the reverse is true.  When `len = MAX_STATIC_VEC + 1`,
+/// after popping the item, all the items residing in the `Vec` are moved back to the fixed-size array (`list`).
+/// The `Vec` will then be empty.
+///
+/// Therefore, if `len <= MAX_STATIC_VEC`, data is in the fixed-size array (`list`).
+/// Otherwise, data is in the `Vec` (`more`).
+///
 /// # Safety
 ///
 /// This type uses some unsafe code (mainly for uninitialized/unused array slots) for efficiency.
@@ -67,12 +94,16 @@ const MAX_STATIC_VEC: usize = 4;
 pub struct StaticVec<T> {
     /// Total number of values held.
     len: usize,
-    /// Static storage. 4 slots should be enough for most cases - i.e. four items of fast, no-allocation access.
+    /// Fixed-size storage for fast, no-allocation access.
-    list: [mem::MaybeUninit<T>; MAX_STATIC_VEC],
+    list: [MaybeUninit<T>; MAX_STATIC_VEC],
     /// Dynamic storage. For spill-overs.
     more: Vec<T>,
 }
 
+/// Maximum slots of fixed-size storage for a `StaticVec`.
+/// 4 slots should be enough for most cases.
+const MAX_STATIC_VEC: usize = 4;
+
 impl<T> Drop for StaticVec<T> {
     fn drop(&mut self) {
         self.clear();
@@ -83,7 +114,7 @@ impl<T> Default for StaticVec<T> {
     fn default() -> Self {
         Self {
             len: 0,
-            list: unsafe_uninit(),
+            list: unsafe { mem::MaybeUninit::uninit().assume_init() },
             more: Vec::new(),
         }
     }
@@ -91,9 +122,18 @@ impl<T> Default for StaticVec<T> {
 
 impl<T: PartialEq> PartialEq for StaticVec<T> {
     fn eq(&self, other: &Self) -> bool {
-        self.len == other.len
+        if self.len != other.len || self.more != other.more {
-            //&& self.list[0..self.len] == other.list[0..self.len]
+            return false;
-            && self.more == other.more
+        }
+
+        if self.len > MAX_STATIC_VEC {
+            return true;
+        }
+
+        unsafe {
+            mem::transmute::<_, &[T; MAX_STATIC_VEC]>(&self.list)
+                == mem::transmute::<_, &[T; MAX_STATIC_VEC]>(&other.list)
+        }
     }
 }
 
@@ -102,10 +142,10 @@ impl<T: Clone> Clone for StaticVec<T> {
         let mut value: Self = Default::default();
         value.len = self.len;
 
-        if self.len <= self.list.len() {
+        if self.is_fixed_storage() {
             for x in 0..self.len {
                 let item: &T = unsafe { mem::transmute(self.list.get(x).unwrap()) };
-                value.list[x] = mem::MaybeUninit::new(item.clone());
+                value.list[x] = MaybeUninit::new(item.clone());
             }
         } else {
             value.more = self.more.clone();
@@ -130,72 +170,118 @@ impl<T> FromIterator<T> for StaticVec<T> {
 }
 
 impl<T> StaticVec<T> {
-    fn extract(value: mem::MaybeUninit<T>) -> T {
-        unsafe { value.assume_init() }
-    }
     /// Create a new `StaticVec`.
     pub fn new() -> Self {
         Default::default()
     }
     /// Empty the `StaticVec`.
     pub fn clear(&mut self) {
-        if self.len <= self.list.len() {
+        if self.is_fixed_storage() {
             for x in 0..self.len {
-                Self::extract(mem::replace(
+                self.extract_from_list(x);
-                    self.list.get_mut(x).unwrap(),
-                    mem::MaybeUninit::uninit(),
-                ));
             }
         } else {
             self.more.clear();
         }
         self.len = 0;
     }
+    /// Extract a `MaybeUninit` into a concrete initialized type.
+    fn extract(value: MaybeUninit<T>) -> T {
+        unsafe { value.assume_init() }
+    }
+    /// Extract an item from the fixed-size array, replacing it with `MaybeUninit::uninit()`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if fixed-size storage is not used, or if the `index` is out of bounds.
+    fn extract_from_list(&mut self, index: usize) -> T {
+        if !self.is_fixed_storage() {
+            panic!("not fixed storage in StaticVec");
+        }
+        if index >= self.len {
+            panic!("index OOB in StaticVec");
+        }
+        Self::extract(mem::replace(
+            self.list.get_mut(index).unwrap(),
+            MaybeUninit::uninit(),
+        ))
+    }
+    /// Set an item into the fixed-size array.
+    /// If `drop` is `true`, the original value is extracted then automatically dropped.
+    ///
+    /// # Panics
+    ///
+    /// Panics if fixed-size storage is not used, or if the `index` is out of bounds.
+    fn set_into_list(&mut self, index: usize, value: T, drop: bool) {
+        if !self.is_fixed_storage() {
+            panic!("not fixed storage in StaticVec");
+        }
+        // Allow setting at most one slot to the right
+        if index > self.len {
+            panic!("index OOB in StaticVec");
+        }
+        let temp = mem::replace(self.list.get_mut(index).unwrap(), MaybeUninit::new(value));
+        if drop {
+            // Extract the original value - which will drop it automatically
+            Self::extract(temp);
+        }
+    }
+    /// Move item in the fixed-size array into the `Vec`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if fixed-size storage is not used, or if the fixed-size storage is not full.
+    fn move_fixed_into_vec(&mut self, num: usize) {
+        if !self.is_fixed_storage() {
+            panic!("not fixed storage in StaticVec");
+        }
+        if self.len != num {
+            panic!("fixed storage is not full in StaticVec");
+        }
+        self.more.extend(
+            self.list
+                .iter_mut()
+                .take(num)
+                .map(|v| mem::replace(v, MaybeUninit::uninit()))
+                .map(Self::extract),
+        );
+    }
+    /// Is data stored in fixed-size storage?
+    fn is_fixed_storage(&self) -> bool {
+        self.len <= MAX_STATIC_VEC
+    }
     /// Push a new value to the end of this `StaticVec`.
     pub fn push<X: Into<T>>(&mut self, value: X) {
-        if self.len == self.list.len() {
+        if self.len == MAX_STATIC_VEC {
-            // Move the fixed list to the Vec
+            self.move_fixed_into_vec(MAX_STATIC_VEC);
-            self.more.extend(
-                self.list
-                    .iter_mut()
-                    .map(|v| mem::replace(v, mem::MaybeUninit::uninit()))
-                    .map(Self::extract),
-            );
             self.more.push(value.into());
-        } else if self.len < self.list.len() {
+        } else if self.is_fixed_storage() {
-            mem::replace(
+            self.set_into_list(self.len, value.into(), false);
-                self.list.get_mut(self.len).unwrap(),
-                mem::MaybeUninit::new(value.into()),
-            );
         } else {
             self.more.push(value.into());
         }
         self.len += 1;
     }
     /// Insert a new value to this `StaticVec` at a particular position.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `index` is out of bounds.
     pub fn insert<X: Into<T>>(&mut self, index: usize, value: X) {
         if index > self.len {
             panic!("index OOB in StaticVec");
         }
 
-        if self.len == self.list.len() {
+        if self.len == MAX_STATIC_VEC {
-            // Move the fixed list to the Vec
+            self.move_fixed_into_vec(MAX_STATIC_VEC);
-            self.more.extend(
-                self.list
-                    .iter_mut()
-                    .map(|v| mem::replace(v, mem::MaybeUninit::uninit()))
-                    .map(Self::extract),
-            );
             self.more.insert(index, value.into());
-        } else if self.len < self.list.len() {
+        } else if self.is_fixed_storage() {
+            // Move all items one slot to the right
             for x in (index..self.len).rev() {
-                let temp = mem::replace(self.list.get_mut(x).unwrap(), mem::MaybeUninit::uninit());
+                let orig_value = self.extract_from_list(x);
-                mem::replace(self.list.get_mut(x + 1).unwrap(), temp);
+                self.set_into_list(x + 1, orig_value, false);
             }
-            mem::replace(
+            self.set_into_list(index, value.into(), false);
-                self.list.get_mut(index).unwrap(),
-                mem::MaybeUninit::new(value.into()),
-            );
         } else {
             self.more.insert(index, value.into());
         }
@@ -207,29 +293,62 @@ impl<T> StaticVec<T> {
     ///
     /// Panics if the `StaticVec` is empty.
     pub fn pop(&mut self) -> T {
-        if self.len <= 0 {
+        if self.is_empty() {
             panic!("nothing to pop!");
         }
 
-        let result = if self.len <= self.list.len() {
+        let result = if self.is_fixed_storage() {
-            Self::extract(mem::replace(
+            self.extract_from_list(self.len - 1)
-                self.list.get_mut(self.len - 1).unwrap(),
-                mem::MaybeUninit::uninit(),
-            ))
         } else {
-            let r = self.more.pop().unwrap();
+            let value = self.more.pop().unwrap();
 
             // Move back to the fixed list
-            if self.more.len() == self.list.len() {
+            if self.more.len() == MAX_STATIC_VEC {
-                for index in (0..self.list.len()).rev() {
+                for index in (0..MAX_STATIC_VEC).rev() {
-                    mem::replace(
+                    let item = self.more.pop().unwrap();
-                        self.list.get_mut(index).unwrap(),
+                    self.set_into_list(index, item, false);
-                        mem::MaybeUninit::new(self.more.pop().unwrap()),
-                    );
                 }
             }
 
-            r
+            value
+        };
+
+        self.len -= 1;
+
+        result
+    }
+    /// Remove a value from this `StaticVec` at a particular position.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `index` is out of bounds.
+    pub fn remove(&mut self, index: usize) -> T {
+        if index >= self.len {
+            panic!("index OOB in StaticVec");
+        }
+
+        let result = if self.is_fixed_storage() {
+            let value = self.extract_from_list(index);
+
+            // Move all items one slot to the left
+            for x in index..self.len - 1 {
+                let orig_value = self.extract_from_list(x + 1);
+                self.set_into_list(x, orig_value, false);
+            }
+
+            value
+        } else {
+            let value = self.more.remove(index);
+
+            // Move back to the fixed list
+            if self.more.len() == MAX_STATIC_VEC {
+                for index in (0..MAX_STATIC_VEC).rev() {
+                    let item = self.more.pop().unwrap();
+                    self.set_into_list(index, item, false);
+                }
+            }
+
+            value
         };
 
         self.len -= 1;
@@ -248,15 +367,15 @@ impl<T> StaticVec<T> {
     ///
     /// # Panics
     ///
-    /// Panics if the index is out of bounds.
+    /// Panics if `index` is out of bounds.
-    pub fn get_ref(&self, index: usize) -> &T {
+    pub fn get(&self, index: usize) -> &T {
         if index >= self.len {
             panic!("index OOB in StaticVec");
         }
 
         let list: &[T; MAX_STATIC_VEC] = unsafe { mem::transmute(&self.list) };
 
-        if self.len <= list.len() {
+        if self.is_fixed_storage() {
             list.get(index).unwrap()
         } else {
             self.more.get(index).unwrap()
@@ -266,7 +385,7 @@ impl<T> StaticVec<T> {
     ///
     /// # Panics
     ///
-    /// Panics if the index is out of bounds.
+    /// Panics if `index` is out of bounds.
     pub fn get_mut(&mut self, index: usize) -> &mut T {
         if index >= self.len {
             panic!("index OOB in StaticVec");
@@ -274,7 +393,7 @@ impl<T> StaticVec<T> {
 
         let list: &mut [T; MAX_STATIC_VEC] = unsafe { mem::transmute(&mut self.list) };
 
-        if self.len <= list.len() {
+        if self.is_fixed_storage() {
             list.get_mut(index).unwrap()
         } else {
             self.more.get_mut(index).unwrap()
@@ -284,7 +403,7 @@ impl<T> StaticVec<T> {
     pub fn iter(&self) -> impl Iterator<Item = &T> {
         let list: &[T; MAX_STATIC_VEC] = unsafe { mem::transmute(&self.list) };
 
-        if self.len <= list.len() {
+        if self.is_fixed_storage() {
             list[..self.len].iter()
         } else {
             self.more.iter()
@@ -294,7 +413,7 @@ impl<T> StaticVec<T> {
     pub fn iter_mut(&mut self) -> impl Iterator<Item = &mut T> {
         let list: &mut [T; MAX_STATIC_VEC] = unsafe { mem::transmute(&mut self.list) };
 
-        if self.len <= list.len() {
+        if self.is_fixed_storage() {
             list[..self.len].iter_mut()
         } else {
             self.more.iter_mut()
@@ -302,18 +421,66 @@ impl<T> StaticVec<T> {
     }
 }
 
+impl<T: 'static> StaticVec<T> {
+    /// Get a mutable iterator to entries in the `StaticVec`.
+    pub fn into_iter(mut self) -> Box<dyn Iterator<Item = T>> {
+        if self.is_fixed_storage() {
+            let mut it = FixedStorageIterator {
+                data: unsafe { mem::MaybeUninit::uninit().assume_init() },
+                index: 0,
+                limit: self.len,
+            };
+
+            for x in 0..self.len {
+                it.data[x] = mem::replace(self.list.get_mut(x).unwrap(), MaybeUninit::uninit());
+            }
+            self.len = 0;
+
+            Box::new(it)
+        } else {
+            Box::new(Vec::from(self).into_iter())
+        }
+    }
+}
+
+/// An iterator that takes control of the fixed-size storage of a `StaticVec` and returns its values.
+struct FixedStorageIterator<T> {
+    data: [MaybeUninit<T>; MAX_STATIC_VEC],
+    index: usize,
+    limit: usize,
+}
+
+impl<T> Iterator for FixedStorageIterator<T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.index >= self.limit {
+            None
+        } else {
+            self.index += 1;
+
+            let value = mem::replace(
+                self.data.get_mut(self.index - 1).unwrap(),
+                MaybeUninit::uninit(),
+            );
+
+            unsafe { Some(value.assume_init()) }
+        }
+    }
+}
+
 impl<T: Default> StaticVec<T> {
     /// Get the item at a particular index, replacing it with the default.
     ///
     /// # Panics
     ///
-    /// Panics if the index is out of bounds.
+    /// Panics if `index` is out of bounds.
-    pub fn get(&mut self, index: usize) -> T {
+    pub fn take(&mut self, index: usize) -> T {
         if index >= self.len {
             panic!("index OOB in StaticVec");
         }
 
-        mem::take(if self.len <= self.list.len() {
+        mem::take(if self.is_fixed_storage() {
             unsafe { mem::transmute(self.list.get_mut(index).unwrap()) }
         } else {
             self.more.get_mut(index).unwrap()
@@ -333,7 +500,7 @@ impl<T> AsRef<[T]> for StaticVec<T> {
     fn as_ref(&self) -> &[T] {
         let list: &[T; MAX_STATIC_VEC] = unsafe { mem::transmute(&self.list) };
 
-        if self.len <= list.len() {
+        if self.is_fixed_storage() {
             &list[..self.len]
         } else {
             &self.more[..]
@@ -345,7 +512,7 @@ impl<T> AsMut<[T]> for StaticVec<T> {
     fn as_mut(&mut self) -> &mut [T] {
         let list: &mut [T; MAX_STATIC_VEC] = unsafe { mem::transmute(&mut self.list) };
 
-        if self.len <= list.len() {
+        if self.is_fixed_storage() {
             &mut list[..self.len]
         } else {
             &mut self.more[..]
@@ -353,20 +520,30 @@ impl<T> AsMut<[T]> for StaticVec<T> {
     }
 }
 
+impl<T> Index<usize> for StaticVec<T> {
+    type Output = T;
+
+    fn index(&self, index: usize) -> &Self::Output {
+        self.get(index)
+    }
+}
+
+impl<T> IndexMut<usize> for StaticVec<T> {
+    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
+        self.get_mut(index)
+    }
+}
+
 impl<T> From<StaticVec<T>> for Vec<T> {
     fn from(mut value: StaticVec<T>) -> Self {
-        if value.len <= value.list.len() {
+        if value.len <= MAX_STATIC_VEC {
-            value
+            value.move_fixed_into_vec(value.len);
-                .list
-                .iter_mut()
-                .map(|v| mem::replace(v, mem::MaybeUninit::uninit()))
-                .map(StaticVec::extract)
-                .collect()
-        } else {
-            let mut arr = Self::new();
-            arr.append(&mut value.more);
-            arr
         }
+        value.len = 0;
+
+        let mut arr = Self::new();
+        arr.append(&mut value.more);
+        arr
     }
 }
 
@@ -375,12 +552,9 @@ impl<T> From<Vec<T>> for StaticVec<T> {
         let mut arr: Self = Default::default();
         arr.len = value.len();
 
-        if arr.len <= arr.list.len() {
+        if arr.len <= MAX_STATIC_VEC {
             for x in (0..arr.len).rev() {
-                mem::replace(
+                arr.set_into_list(x, value.pop().unwrap(), false);
-                    arr.list.get_mut(x).unwrap(),
-                    mem::MaybeUninit::new(value.pop().unwrap()),
-                );
             }
         } else {
             arr.more = value;

tests/modules.rs

@@ -84,28 +84,39 @@ fn test_module_resolver() -> Result<(), Box<EvalAltResult>> {
 
     assert!(matches!(
         *engine
-            .eval::<()>(
+            .eval::<INT>(
                 r#"
+                    let x = 0;
+
                     for x in range(0, 10) {
                         import "hello" as h;
+                        x += h::answer;
                     }
+
+                    x
             "#
             )
             .expect_err("should error"),
         EvalAltResult::ErrorTooManyModules(_)
     ));
 
+    #[cfg(not(feature = "no_function"))]
     assert!(matches!(
         *engine
-            .eval::<()>(
+            .eval::<INT>(
                 r#"
+                    let x = 0;
+
                     fn foo() {
                         import "hello" as h;
+                        x += h::answer;
                     }
 
                     for x in range(0, 10) {
                         foo();
                     }
+
+                    x
             "#
             )
             .expect_err("should error"),
@@ -114,6 +125,7 @@ fn test_module_resolver() -> Result<(), Box<EvalAltResult>> {
 
     engine.set_max_modules(0);
 
+    #[cfg(not(feature = "no_function"))]
     engine.eval::<()>(
         r#"
             fn foo() {

tests/operations.rs

@@ -43,20 +43,40 @@ fn test_max_operations_functions() -> Result<(), Box<EvalAltResult>> {
 
     engine.eval::<()>(
         r#"
+                print("Test1");
+                let x = 0;
+
+                while x < 28 {
+                    print(x);
+                    x += 1;
+                }
+            "#,
+    )?;
+
+    #[cfg(not(feature = "no_function"))]
+    engine.eval::<()>(
+        r#"
+                print("Test2");
                 fn inc(x) { x + 1 }
                 let x = 0;
                 while x < 20 { x = inc(x); }
             "#,
     )?;
 
+    #[cfg(not(feature = "no_function"))]
     assert!(matches!(
         *engine
             .eval::<()>(
                 r#"
+                    print("Test3");
                     fn inc(x) { x + 1 }
                     let x = 0;
-                    while x < 1000 { x = inc(x); }
+
-        "#
+                    while x < 28 {
+                        print(x);
+                        x = inc(x);
+                    }
+            "#,
             )
             .expect_err("should error"),
         EvalAltResult::ErrorTooManyOperations(_)