Add for statement and range function; New register_box_fn for functions returning Box<dyn Any> (which should not be boxed again); Register standard utility functions in library (e.g. print, string concat).

scripts/for1.rhai

@@ -0,0 +1,15 @@
+let arr = [1,2,3,4]
+for a in arr {
+    for b in [10,20] {
+        print(a)
+        print(b)
+    }
+    if a == 3 {
+        break;
+    }
+}
+//print(a)
+
+for i in range(0,5) {
+    print(i)
+}

src/any.rs

@@ -76,7 +76,7 @@ impl Clone for Box<dyn Any> {
 
 impl fmt::Debug for dyn Any {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.pad("Any")
+        f.pad("?")
     }
 }
 

src/engine.rs

@@ -4,20 +4,25 @@ use std::collections::HashMap;
 use std::error::Error;
 use std::fmt;
 use std::ops::{Add, BitAnd, BitOr, BitXor, Div, Mul, Neg, Rem, Shl, Shr, Sub};
-use std::sync::Arc;
+use std::{convert::TryInto, sync::Arc};
 
 use crate::any::{Any, AnyExt};
 use crate::call::FunArgs;
-use crate::fn_register::RegisterFn;
+use crate::fn_register::{RegisterBoxFn, RegisterFn};
 use crate::parser::{lex, parse, Expr, FnDef, Stmt};
+use fmt::{Debug, Display};
+
+type Array = Vec<Box<dyn Any>>;
 
 #[derive(Debug)]
 pub enum EvalAltResult {
     ErrorFunctionNotFound(String),
     ErrorFunctionArgMismatch,
     ErrorArrayOutOfBounds(usize, i64),
+    ErrorArrayMismatch,
     ErrorIndexMismatch,
     ErrorIfGuardMismatch,
+    ErrorForMismatch,
     ErrorVariableNotFound(String),
     ErrorAssignmentToUnknownLHS,
     ErrorMismatchOutputType(String),
@@ -46,10 +51,12 @@ impl PartialEq for EvalAltResult {
             (&ErrorFunctionNotFound(ref a), &ErrorFunctionNotFound(ref b)) => a == b,
             (&ErrorFunctionArgMismatch, &ErrorFunctionArgMismatch) => true,
             (&ErrorIndexMismatch, &ErrorIndexMismatch) => true,
+            (&ErrorArrayMismatch, &ErrorArrayMismatch) => true,
             (&ErrorArrayOutOfBounds(max1, index1), &ErrorArrayOutOfBounds(max2, index2)) => {
                 max1 == max2 && index1 == index2
             }
             (&ErrorIfGuardMismatch, &ErrorIfGuardMismatch) => true,
+            (&ErrorForMismatch, &ErrorForMismatch) => true,
             (&ErrorVariableNotFound(ref a), &ErrorVariableNotFound(ref b)) => a == b,
             (&ErrorAssignmentToUnknownLHS, &ErrorAssignmentToUnknownLHS) => true,
             (&ErrorMismatchOutputType(ref a), &ErrorMismatchOutputType(ref b)) => a == b,
@@ -67,12 +74,14 @@ impl Error for EvalAltResult {
             EvalAltResult::ErrorFunctionNotFound(_) => "Function not found",
             EvalAltResult::ErrorFunctionArgMismatch => "Function argument types do not match",
             EvalAltResult::ErrorIndexMismatch => "Array access expects integer index",
+            EvalAltResult::ErrorArrayMismatch => "Indexing can only be performed on an array",
             EvalAltResult::ErrorArrayOutOfBounds(_, index) if index < 0 => {
                 "Array access expects non-negative index"
             }
             EvalAltResult::ErrorArrayOutOfBounds(max, _) if max == 0 => "Access of empty array",
             EvalAltResult::ErrorArrayOutOfBounds(_, _) => "Array index out of bounds",
             EvalAltResult::ErrorIfGuardMismatch => "If guards expect boolean expression",
+            EvalAltResult::ErrorForMismatch => "For loops expect array",
             EvalAltResult::ErrorVariableNotFound(_) => "Variable not found",
             EvalAltResult::ErrorAssignmentToUnknownLHS => {
                 "Assignment to an unsupported left-hand side"
@@ -107,7 +116,7 @@ impl fmt::Display for EvalAltResult {
                 EvalAltResult::ErrorArrayOutOfBounds(max, index) => {
                     write!(f, "{} (max {}): {}", self.description(), max - 1, index)
                 }
-                _ => write!(f, "{}", self.description()),
+                err => write!(f, "{}", err.description()),
             }
         }
     }
@@ -119,6 +128,8 @@ pub struct FnSpec {
     args: Option<Vec<TypeId>>,
 }
 
+type IteratorFn = dyn Fn(&Box<dyn Any>) -> Box<dyn Iterator<Item = Box<dyn Any>>>;
+
 /// Rhai's engine type. This is what you use to run Rhai scripts
 ///
 /// ```rust
@@ -137,6 +148,7 @@ pub struct FnSpec {
 pub struct Engine {
     /// A hashmap containing all functions known to the engine
     pub fns: HashMap<FnSpec, Arc<FnIntExt>>,
+    pub type_iterators: HashMap<TypeId, Arc<IteratorFn>>,
 }
 
 pub enum FnIntExt {
@@ -187,16 +199,14 @@ impl Engine {
         debug_println!(
             "Trying to call function {:?} with args {:?}",
             ident,
-            args.iter().map(|x| (&**x).type_id()).collect::<Vec<_>>()
+            args.iter()
+                .map(|x| Any::type_name(&**x))
+                .collect::<Vec<_>>()
         );
 
         let spec = FnSpec {
             ident: ident.clone(),
-            args: Some(
+            args: Some(args.iter().map(|a| Any::type_id(&**a)).collect()),
-                args.iter()
-                    .map(|a| <dyn Any as Any>::type_id(&**a))
-                    .collect(),
-            ),
         };
 
         self.fns
@@ -248,6 +258,14 @@ impl Engine {
         // currently a no-op, exists for future extensibility
     }
 
+    /// Register an iterator adapter for a type.
+    pub fn register_iterator<T: Any, F>(&mut self, f: F)
+    where
+        F: 'static + Fn(&Box<dyn Any>) -> Box<dyn Iterator<Item = Box<dyn Any>>>,
+    {
+        self.type_iterators.insert(TypeId::of::<T>(), Arc::new(f));
+    }
+
     /// Register a get function for a member of a registered type
     pub fn register_get<T: Clone + Any, U: Clone + Any, F>(&mut self, name: &str, get_fn: F)
     where
@@ -290,7 +308,7 @@ impl Engine {
 
         match *dot_rhs {
             Expr::FnCall(ref fn_name, ref args) => {
-                let mut args: Vec<Box<dyn Any>> = args
+                let mut args: Array = args
                     .iter()
                     .map(|arg| self.eval_expr(scope, arg))
                     .collect::<Result<Vec<_>, _>>()?;
@@ -311,9 +329,13 @@ impl Engine {
 
                 let mut val = self.call_fn_raw(get_fn_name, vec![this_ptr])?;
 
-                ((*val).downcast_mut() as Option<&mut Vec<Box<dyn Any>>>)
+                ((*val).downcast_mut() as Option<&mut Array>)
-                    .and_then(|arr| idx.downcast_ref::<i64>().map(|idx| (arr, *idx)))
+                    .ok_or(EvalAltResult::ErrorArrayMismatch)
-                    .ok_or(EvalAltResult::ErrorIndexMismatch)
+                    .and_then(|arr| {
+                        idx.downcast_ref::<i64>()
+                            .map(|idx| (arr, *idx))
+                            .ok_or(EvalAltResult::ErrorIndexMismatch)
+                    })
                     .and_then(|(arr, idx)| match idx {
                         x if x < 0 => Err(EvalAltResult::ErrorArrayOutOfBounds(0, x)),
                         x => arr
@@ -367,8 +389,8 @@ impl Engine {
             x => x as usize,
         };
         let (idx_sc, val) = Self::search_scope(scope, id, |val| {
-            ((*val).downcast_mut() as Option<&mut Vec<Box<dyn Any>>>)
+            ((*val).downcast_mut() as Option<&mut Array>)
-                .ok_or(EvalAltResult::ErrorIndexMismatch)
+                .ok_or(EvalAltResult::ErrorArrayMismatch)
                 .and_then(|arr| {
                     arr.get(idx)
                         .cloned()
@@ -402,7 +424,7 @@ impl Engine {
 
                 // In case the expression mutated `target`, we need to reassign it because
                 // of the above `clone`.
-                scope[sc_idx].1.downcast_mut::<Vec<Box<dyn Any>>>().unwrap()[idx] = target;
+                scope[sc_idx].1.downcast_mut::<Array>().unwrap()[idx] = target;
 
                 value
             }
@@ -465,7 +487,7 @@ impl Engine {
 
                 // In case the expression mutated `target`, we need to reassign it because
                 // of the above `clone`.
-                scope[sc_idx].1.downcast_mut::<Vec<Box<dyn Any>>>().unwrap()[idx] = target;
+                scope[sc_idx].1.downcast_mut::<Array>().unwrap()[idx] = target;
 
                 value
             }
@@ -509,24 +531,27 @@ impl Engine {
 
                         for &mut (ref name, ref mut val) in &mut scope.iter_mut().rev() {
                             if *id == *name {
-                                if let Some(&i) = idx.downcast_ref::<i64>() {
+                                return if let Some(&i) = idx.downcast_ref::<i64>() {
                                     if let Some(arr_typed) =
-                                        (*val).downcast_mut() as Option<&mut Vec<Box<dyn Any>>>
+                                        (*val).downcast_mut() as Option<&mut Array>
                                     {
-                                        return if i < 0 {
+                                        if i < 0 {
                                             Err(EvalAltResult::ErrorArrayOutOfBounds(0, i))
                                         } else if i as usize >= arr_typed.len() {
-                                            Err(EvalAltResult::ErrorArrayOutOfBounds(arr_typed.len(), i))
+                                            Err(EvalAltResult::ErrorArrayOutOfBounds(
+                                                arr_typed.len(),
+                                                i,
+                                            ))
                                         } else {
                                             arr_typed[i as usize] = rhs_val;
                                             Ok(Box::new(()))
-                                        };
+                                        }
                                     } else {
-                                        return Err(EvalAltResult::ErrorIndexMismatch);
+                                        Err(EvalAltResult::ErrorIndexMismatch)
                                     }
                                 } else {
-                                    return Err(EvalAltResult::ErrorIndexMismatch);
+                                    Err(EvalAltResult::ErrorIndexMismatch)
-                                }
+                                };
                             }
                         }
 
@@ -553,7 +578,7 @@ impl Engine {
                 fn_name.to_owned(),
                 args.iter()
                     .map(|ex| self.eval_expr(scope, ex))
-                    .collect::<Result<Vec<Box<dyn Any>>, _>>()?
+                    .collect::<Result<Array, _>>()?
                     .iter_mut()
                     .map(|b| b.as_mut())
                     .collect(),
@@ -635,6 +660,26 @@ impl Engine {
                     _ => (),
                 }
             },
+            Stmt::For(ref name, ref expr, ref body) => {
+                let arr = self.eval_expr(scope, expr)?;
+                let tid = Any::type_id(&*arr);
+                if let Some(iter_fn) = self.type_iterators.get(&tid) {
+                    scope.push((name.clone(), Box::new(())));
+                    let idx = scope.len() - 1;
+                    for a in iter_fn(&arr) {
+                        scope[idx].1 = a;
+                        match self.eval_stmt(scope, body) {
+                            Err(EvalAltResult::LoopBreak) => break,
+                            Err(x) => return Err(x),
+                            _ => (),
+                        }
+                    }
+                    scope.remove(idx);
+                    Ok(Box::new(()))
+                } else {
+                    return Err(EvalAltResult::ErrorForMismatch);
+                }
+            }
             Stmt::Break => Err(EvalAltResult::LoopBreak),
             Stmt::Return => Err(EvalAltResult::Return(Box::new(()))),
             Stmt::ReturnWithVal(ref a) => {
@@ -824,6 +869,30 @@ impl Engine {
             )
         }
 
+        macro_rules! reg_func1 {
+            ($engine:expr, $x:expr, $op:expr, $r:ty, $( $y:ty ),*) => (
+                $(
+                    $engine.register_fn($x, $op as fn(x: $y)->$r);
+                )*
+            )
+        }
+
+        macro_rules! reg_func2 {
+            ($engine:expr, $x:expr, $op:expr, $v:ty, $r:ty, $( $y:ty ),*) => (
+                $(
+                    $engine.register_fn($x, $op as fn(x: $v, y: $y)->$r);
+                )*
+            )
+        }
+
+        macro_rules! reg_func2b {
+            ($engine:expr, $x:expr, $op:expr, $v:ty, $r:ty, $( $y:ty ),*) => (
+                $(
+                    $engine.register_fn($x, $op as fn(y: $y, x: $v)->$r);
+                )*
+            )
+        }
+
         fn add<T: Add>(x: T, y: T) -> <T as Add>::Output {
             x + y
         }
@@ -936,12 +1005,91 @@ impl Engine {
         // FIXME?  Registering array lookups are a special case because we want to return boxes
         // directly let ent = engine.fns.entry("[]".to_string()).or_insert_with(Vec::new);
         // (*ent).push(FnType::ExternalFn2(Box::new(idx)));
+
+        // Register print and debug
+        fn print_debug<T: Debug>(x: T) {
+            println!("{:?}", x);
+        }
+        fn print<T: Display>(x: T) {
+            println!("{}", x);
+        }
+
+        reg_func1!(engine, "print", print, (), i32, i64, u32, u64);
+        reg_func1!(engine, "print", print, (), f32, f64, bool, String);
+        reg_func1!(engine, "print", print_debug, (), Array);
+
+        reg_func1!(engine, "debug", print_debug, (), i32, i64, u32, u64);
+        reg_func1!(engine, "debug", print_debug, (), f32, f64, bool, String);
+        reg_func1!(engine, "debug", print_debug, (), Array);
+
+        // Register array functions
+        fn push<T: Any + 'static>(list: &mut Array, item: T) {
+            list.push(Box::new(item));
+        }
+        fn pop(list: &mut Array) -> Box<dyn Any> {
+            list.pop().unwrap()
+        }
+        fn shift(list: &mut Array) -> Box<dyn Any> {
+            list.remove(0)
+        }
+        fn len(list: &mut Array) -> i64 {
+            list.len().try_into().unwrap()
+        }
+
+        reg_func2!(engine, "push", push, &mut Array, (), i32, i64, u32, u64);
+        reg_func2!(engine, "push", push, &mut Array, (), f32, f64, bool);
+        reg_func2!(engine, "push", push, &mut Array, (), String, Array);
+
+        engine.register_box_fn("pop", pop);
+        engine.register_box_fn("shift", shift);
+        engine.register_fn("len", len);
+
+        // Register string concatenate functions
+        fn prepend<T: Display>(x: T, y: String) -> String {
+            format!("{}{}", x, y)
+        }
+        fn append<T: Display>(x: &mut String, y: T) -> String {
+            format!("{}{}", x, y)
+        }
+        fn prepend_array(x: Array, y: String) -> String {
+            format!("{:?}{}", x, y)
+        }
+        fn append_array(x: &mut String, y: Array) -> String {
+            format!("{}{:?}", x, y)
+        }
+
+        reg_func2!(engine, "+", append, &mut String, String, i32, i64);
+        reg_func2!(engine, "+", append, &mut String, String, u32, u64);
+        reg_func2!(engine, "+", append, &mut String, String, f32, f64, bool);
+        engine.register_fn("+", append_array);
+
+        reg_func2b!(engine, "+", prepend, String, String, i32, i64, u32, u64, f32, f64, bool);
+        engine.register_fn("+", prepend_array);
+
+        // Register array iterator
+        engine.register_iterator::<Array, _>(|a| {
+            Box::new(a.downcast_ref::<Array>().unwrap().clone().into_iter())
+        });
+
+        // Register range function
+        use std::ops::Range;
+        engine.register_iterator::<Range<i64>, _>(|a| {
+            Box::new(
+                a.downcast_ref::<Range<i64>>()
+                    .unwrap()
+                    .clone()
+                    .map(|n| Box::new(n) as Box<dyn Any>),
+            )
+        });
+
+        engine.register_fn("range", |i1: i64, i2: i64| (i1..i2));
     }
 
     /// Make a new engine
     pub fn new() -> Engine {
         let mut engine = Engine {
             fns: HashMap::new(),
+            type_iterators: HashMap::new(),
         };
 
         Engine::register_default_lib(&mut engine);

src/fn_register.rs

@@ -6,6 +6,9 @@ use crate::engine::{Engine, EvalAltResult};
 pub trait RegisterFn<FN, ARGS, RET> {
     fn register_fn(&mut self, name: &str, f: FN);
 }
+pub trait RegisterBoxFn<FN, ARGS> {
+    fn register_box_fn(&mut self, name: &str, f: FN);
+}
 
 pub struct Ref<A>(A);
 pub struct Mut<A>(A);
@@ -44,7 +47,37 @@ macro_rules! def_register {
 
                     // Call the user-supplied function using ($clone) to
                     // potentially clone the value, otherwise pass the reference.
-                    Ok(Box::new(f($(($clone)($par)),*)) as Box<dyn Any>)
+                    let r = f($(($clone)($par)),*);
+                    Ok(Box::new(r) as Box<dyn Any>)
+                };
+                self.register_fn_raw(name.to_owned(), Some(vec![$(TypeId::of::<$par>()),*]), Box::new(fun));
+            }
+        }
+
+        impl<$($par,)* FN> RegisterBoxFn<FN, ($($mark,)*)> for Engine
+        where
+            $($par: Any + Clone,)*
+            FN: Fn($($param),*) -> Box<dyn Any> + 'static
+        {
+            fn register_box_fn(&mut self, name: &str, f: FN) {
+                let fun = move |mut args: Vec<&mut dyn Any>| {
+                    // Check for length at the beginning to avoid
+                    // per-element bound checks.
+                    if args.len() != count_args!($($par)*) {
+                        return Err(EvalAltResult::ErrorFunctionArgMismatch);
+                    }
+
+                    #[allow(unused_variables, unused_mut)]
+                    let mut drain = args.drain(..);
+                    $(
+                    // Downcast every element, return in case of a type mismatch
+                    let $par = ((*drain.next().unwrap()).downcast_mut() as Option<&mut $par>)
+                        .ok_or(EvalAltResult::ErrorFunctionArgMismatch)?;
+                    )*
+
+                    // Call the user-supplied function using ($clone) to
+                    // potentially clone the value, otherwise pass the reference.
+                    Ok(f($(($clone)($par)),*))
                 };
                 self.register_fn_raw(name.to_owned(), Some(vec![$(TypeId::of::<$par>()),*]), Box::new(fun));
             }

src/lib.rs

@@ -47,4 +47,4 @@ mod parser;
 
 pub use any::Any;
 pub use engine::{Engine, EvalAltResult, Scope};
-pub use fn_register::RegisterFn;
+pub use fn_register::{RegisterBoxFn, RegisterFn};

src/parser.rs

@@ -89,6 +89,7 @@ pub enum Stmt {
     IfElse(Box<Expr>, Box<Stmt>, Box<Stmt>),
     While(Box<Expr>, Box<Stmt>),
     Loop(Box<Stmt>),
+    For(String, Box<Expr>, Box<Stmt>),
     Var(String, Option<Box<Expr>>),
     Block(Vec<Stmt>),
     Expr(Box<Expr>),
@@ -175,6 +176,8 @@ pub enum Token {
     ModuloAssign,
     PowerOf,
     PowerOfAssign,
+    For,
+    In,
     LexErr(LexError),
 }
 
@@ -230,6 +233,7 @@ impl Token {
             ModuloAssign     |
             Return           |
             PowerOf          |
+            In               |
             PowerOfAssign => true,
             _ => false,
         }
@@ -505,6 +509,8 @@ impl<'a> TokenIterator<'a> {
                         "break" => return Some(Token::Break),
                         "return" => return Some(Token::Return),
                         "fn" => return Some(Token::Fn),
+                        "for" => return Some(Token::For),
+                        "in" => return Some(Token::In),
                         x => return Some(Token::Identifier(x.to_string())),
                     }
                 }
@@ -1102,6 +1108,26 @@ fn parse_loop<'a>(input: &mut Peekable<TokenIterator<'a>>) -> Result<Stmt, Parse
     Ok(Stmt::Loop(Box::new(body)))
 }
 
+fn parse_for<'a>(input: &mut Peekable<TokenIterator<'a>>) -> Result<Stmt, ParseError> {
+    input.next();
+
+    let name = match input.next() {
+        Some(Token::Identifier(ref s)) => s.clone(),
+        _ => return Err(ParseError::VarExpectsIdentifier),
+    };
+
+    match input.next() {
+        Some(Token::In) => {}
+        _ => return Err(ParseError::VarExpectsIdentifier),
+    }
+
+    let expr = parse_expr(input)?;
+
+    let body = parse_block(input)?;
+
+    Ok(Stmt::For(name, Box::new(expr), Box::new(body)))
+}
+
 fn parse_var<'a>(input: &mut Peekable<TokenIterator<'a>>) -> Result<Stmt, ParseError> {
     input.next();
 
@@ -1168,6 +1194,7 @@ fn parse_stmt<'a>(input: &mut Peekable<TokenIterator<'a>>) -> Result<Stmt, Parse
         Some(&Token::If) => parse_if(input),
         Some(&Token::While) => parse_while(input),
         Some(&Token::Loop) => parse_loop(input),
+        Some(&Token::For) => parse_for(input),
         Some(&Token::Break) => {
             input.next();
             Ok(Stmt::Break)

tests/for.rs

@@ -0,0 +1,24 @@
+use rhai::Engine;
+
+#[test]
+fn test_for() {
+    let mut engine = Engine::new();
+
+    let script = r"
+        let sum1 = 0;
+        let sum2 = 0;
+        let inputs = [1, 2, 3, 4, 5];
+
+        for x in inputs {
+            sum1 += x;
+        }
+
+        for x in range(1, 6) {
+            sum2 += x;
+        }
+
+        sum1 + sum2
+    ";
+
+    assert_eq!(engine.eval::<i64>(script).unwrap(), 30);
+}