Add ranged-for loops

closes [#145]

cheatsheet.md

@@ -111,6 +111,7 @@ chai.add_global_const(chaiscript::const_var(somevar), "somevar"); // global cons
 chai.add_global(chaiscript::var(somevar), "somevar"); // global non-const, throws if object exists
 chai.set_global(chaiscript::var(somevar), "somevar"); // global non-const, overwrites existing object
 ```
+
 # Using STL
 ChaiScript recognize many types from STL, but you have to add specific instantiation yourself.
 
@@ -260,6 +261,23 @@ if (g2.is_var_undef()) { g2 = 4; } // only initialize g2 once, if global decl hi
 GLOBAL g3; // all upper case version also accepted
 ```
 
+## Looping
+
+```
+// c-style for loops
+for (var i = 0; i < 100; ++i) { print(i); }
+```
+
+```
+// while
+while (some_condition()) { /* do something */ }
+```
+
+```
+// ranged for
+for (x : [1,2,3]) { print(i); }
+```
+
 ## Built in Types
 
 ```

include/chaiscript/dispatchkit/dispatchkit.hpp

@@ -462,6 +462,26 @@ namespace chaiscript
           add_object(name, std::move(obj));
         }
 
+        /// Adds a named object to the current scope
+        /// \warning This version does not check the validity of the name
+        /// it is meant for internal use only
+        Boxed_Value &add_get_object(const std::string &t_name, Boxed_Value obj, Stack_Holder &t_holder)
+        {
+          auto &stack_elem = get_stack_data(t_holder).back();
+
+          if (std::any_of(stack_elem.begin(), stack_elem.end(),
+              [&](const std::pair<std::string, Boxed_Value> &o) {
+                return o.first == t_name;
+              }))
+          {
+            throw chaiscript::exception::name_conflict_error(t_name);
+          }
+
+          stack_elem.emplace_back(t_name, std::move(obj));
+          return stack_elem.back().second;
+        }
+
+
         /// Adds a named object to the current scope
         /// \warning This version does not check the validity of the name
         /// it is meant for internal use only
@@ -477,7 +497,7 @@ namespace chaiscript
             throw chaiscript::exception::name_conflict_error(t_name);
           }
 
-          get_stack_data(t_holder).back().emplace_back(t_name, std::move(obj));
+          stack_elem.emplace_back(t_name, std::move(obj));
         }
 
 
@@ -1478,8 +1498,12 @@ namespace chaiscript
           return m_conversions.saves();
         }
 
+        Boxed_Value &add_get_object(const std::string &t_name, Boxed_Value obj) const {
+          return m_engine.get().add_get_object(t_name, std::move(obj), m_stack_holder.get());
+        }
+
         void add_object(const std::string &t_name, Boxed_Value obj) const {
-          m_engine.get().add_object(t_name, std::move(obj), m_stack_holder.get());
+          return m_engine.get().add_object(t_name, std::move(obj), m_stack_holder.get());
         }
 
         Boxed_Value get_object(const std::string &t_name, std::atomic_uint_fast32_t &t_loc) const {

include/chaiscript/language/chaiscript_common.hpp

@@ -58,7 +58,7 @@ namespace chaiscript
   /// Types of AST nodes available to the parser and eval
   enum class AST_Node_Type { Id, Fun_Call, Unused_Return_Fun_Call, Arg_List, Equation, Var_Decl,
     Array_Call, Dot_Access,
-    Lambda, Block, Scopeless_Block, Def, While, If, For, Inline_Array, Inline_Map, Return, File, Prefix, Break, Continue, Map_Pair, Value_Range,
+    Lambda, Block, Scopeless_Block, Def, While, If, For, Ranged_For, Inline_Array, Inline_Map, Return, File, Prefix, Break, Continue, Map_Pair, Value_Range,
     Inline_Range, Try, Catch, Finally, Method, Attr_Decl,  
     Logical_And, Logical_Or, Reference, Switch, Case, Default, Ternary_Cond, Noop, Class, Binary, Arg, Global_Decl, Constant, Compiled
   };
@@ -71,7 +71,7 @@ namespace chaiscript
     const char *ast_node_type_to_string(AST_Node_Type ast_node_type) {
       static const char * const ast_node_types[] = { "Id", "Fun_Call", "Unused_Return_Fun_Call", "Arg_List", "Equation", "Var_Decl",
                                     "Array_Call", "Dot_Access", 
-                                    "Lambda", "Block", "Scopeless_Block", "Def", "While", "If", "For", "Inline_Array", "Inline_Map", "Return", "File", "Prefix", "Break", "Continue", "Map_Pair", "Value_Range",
+                                    "Lambda", "Block", "Scopeless_Block", "Def", "While", "If", "For", "Ranged_For", "Inline_Array", "Inline_Map", "Return", "File", "Prefix", "Break", "Continue", "Map_Pair", "Value_Range",
                                     "Inline_Range", "Try", "Catch", "Finally", "Method", "Attr_Decl",
                                     "Logical_And", "Logical_Or", "Reference", "Switch", "Case", "Default", "Ternary Condition", "Noop", "Class", "Binary", "Arg", "Global_Decl", "Constant", "Compiled"};
 

include/chaiscript/language/chaiscript_eval.hpp

@@ -844,6 +844,89 @@ namespace chaiscript
         }
     };
 
+    template<typename T>
+    struct Ranged_For_AST_Node final : AST_Node_Impl<T> {
+        Ranged_For_AST_Node(std::string t_ast_node_text, Parse_Location t_loc, std::vector<AST_Node_Impl_Ptr<T>> t_children) :
+          AST_Node_Impl<T>(std::move(t_ast_node_text), AST_Node_Type::Ranged_For, std::move(t_loc), std::move(t_children)),
+          m_range_loc(0),
+          m_empty_loc(0),
+          m_front_loc(0),
+          m_pop_front_loc(0)
+          { assert(this->children.size() == 3); }
+
+        Boxed_Value eval_internal(const chaiscript::detail::Dispatch_State &t_ss) const override{
+          const auto get_function = [&t_ss](const std::string &t_name, auto &t_hint){
+            uint_fast32_t hint = t_hint;
+            auto funs = t_ss->get_function(t_name, hint);
+            if (funs.first != hint) t_hint = uint_fast32_t(funs.first);
+            return std::move(funs.second);
+          };
+
+          const auto call_function = [&t_ss](const auto &t_funcs, const Boxed_Value &t_param) {
+            return dispatch::dispatch(*t_funcs, {t_param}, t_ss.conversions());
+          };
+
+
+          const std::string &loop_var_name = this->children[0]->text;
+          Boxed_Value range_expression_result = this->children[1]->eval(t_ss);
+
+
+          const auto do_loop = [&loop_var_name, &t_ss, this](const auto &ranged_thing){
+            try {
+              chaiscript::eval::detail::Scope_Push_Pop spp(t_ss);
+              Boxed_Value &obj = t_ss.add_get_object(loop_var_name, void_var());
+              for (auto loop_var : ranged_thing) {
+                obj = Boxed_Value(std::move(loop_var));
+                try {
+                  this->children[2]->eval(t_ss);
+                } catch (detail::Continue_Loop &) {
+                }
+              }
+            } catch (detail::Break_Loop &) {
+              // loop broken
+            }
+            return void_var();
+          };
+
+          if (range_expression_result.get_type_info().bare_equal_type_info(typeid(std::vector<Boxed_Value>))) {
+            return do_loop(boxed_cast<const std::vector<Boxed_Value> &>(range_expression_result));
+          } else if (range_expression_result.get_type_info().bare_equal_type_info(typeid(std::map<std::string, Boxed_Value>))) {
+            return do_loop(boxed_cast<const std::map<std::string, Boxed_Value> &>(range_expression_result));
+          } else {
+            const auto range_funcs = get_function("range", m_range_loc);
+            const auto empty_funcs = get_function("empty", m_empty_loc);
+            const auto front_funcs = get_function("front", m_front_loc);
+            const auto pop_front_funcs = get_function("pop_front", m_pop_front_loc);
+
+            try {
+              const auto range_obj = call_function(range_funcs, range_expression_result);
+              chaiscript::eval::detail::Scope_Push_Pop spp(t_ss);
+              Boxed_Value &obj = t_ss.add_get_object(loop_var_name, void_var());
+              while (!boxed_cast<bool>(call_function(empty_funcs, range_obj))) {
+                obj = call_function(front_funcs, range_obj);
+                try {
+                  this->children[2]->eval(t_ss);
+                } catch (detail::Continue_Loop &) {
+                }
+                call_function(pop_front_funcs, range_obj);
+              }
+            } catch (detail::Break_Loop &) {
+              // loop broken
+            }
+            return void_var();
+          }
+
+        }
+
+private:
+        mutable std::atomic_uint_fast32_t m_range_loc;
+        mutable std::atomic_uint_fast32_t m_empty_loc;
+        mutable std::atomic_uint_fast32_t m_front_loc;
+        mutable std::atomic_uint_fast32_t m_pop_front_loc;
+
+    };
+
+
     template<typename T>
     struct For_AST_Node final : AST_Node_Impl<T> {
         For_AST_Node(std::string t_ast_node_text, Parse_Location t_loc, std::vector<AST_Node_Impl_Ptr<T>> t_children) :

include/chaiscript/language/chaiscript_parser.hpp

@@ -1647,14 +1647,20 @@ namespace chaiscript
         return retval;
       }
 
+      /// Reads the ranged `for` conditions from input
+      bool Range_Expression() {
+        // the first element will have already been captured by the For_Guards() call that preceeds it
+        return Char(':') && Equation();
+      }
 
-      /// Reads the C-style for conditions from input
+
+      /// Reads the C-style `for` conditions from input
       bool For_Guards() {
         if (!(Equation() && Eol()))
         {
           if (!Eol())
           {
-            throw exception::eval_error("'for' loop initial statment missing", File_Position(m_position.line, m_position.col), *m_filename);
+            return false;
           } else {
             m_match_stack.push_back(chaiscript::make_shared<eval::AST_Node_Impl<Tracer>, eval::Noop_AST_Node<Tracer>>());
           }
@@ -1664,7 +1670,7 @@ namespace chaiscript
         {
           if (!Eol())
           {
-            throw exception::eval_error("'for' loop condition missing", File_Position(m_position.line, m_position.col), *m_filename);
+            return false;
           } else {
             m_match_stack.push_back(chaiscript::make_shared<eval::AST_Node_Impl<Tracer>, eval::Noop_AST_Node<Tracer>>());
           }
@@ -1692,7 +1698,8 @@ namespace chaiscript
             throw exception::eval_error("Incomplete 'for' expression", File_Position(m_position.line, m_position.col), *m_filename);
           }
 
-          if (!(For_Guards() && Char(')'))) {
+          const bool classic_for = For_Guards() && Char(')');
+          if (!classic_for && !(Range_Expression() && Char(')'))) {
             throw exception::eval_error("Incomplete 'for' expression", File_Position(m_position.line, m_position.col), *m_filename);
           }
 
@@ -1702,7 +1709,11 @@ namespace chaiscript
             throw exception::eval_error("Incomplete 'for' block", File_Position(m_position.line, m_position.col), *m_filename);
           }
 
+          if (classic_for) {
             build_match<eval::For_AST_Node<Tracer>>(prev_stack_top);
+          } else {
+            build_match<eval::Ranged_For_AST_Node<Tracer>>(prev_stack_top);
+          }
         }
 
         return retval;

unittests/ranged_for.chai

@@ -0,0 +1,21 @@
+var sum = 0;
+
+for (x : [1,2,3,4]) {
+  sum += x;
+}
+
+assert_equal(sum, 10)
+
+var result = 0.0;
+
+for (x : retro(range([1,2,3,4]))) {
+  if (result == 0.0) {
+    result = x;
+  } else {
+    result /= x;
+  }
+}
+
+assert_true(result > .6 && result < .7);
+
+