From f6c69f28265e8b5ae195102418893a1b5c4621b7 Mon Sep 17 00:00:00 2001
From: Jason Turner <jason@emptycrate.com>
Date: Mon, 25 Apr 2016 21:32:48 -0600
Subject: [PATCH] Allow folding of if blocks

---
 .../chaiscript/language/chaiscript_engine.hpp |  4 ++--
 .../chaiscript/language/chaiscript_eval.hpp   |  2 +-
 .../language/chaiscript_optimizer.hpp         | 20 +++++++++++++++++++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/include/chaiscript/language/chaiscript_engine.hpp b/include/chaiscript/language/chaiscript_engine.hpp
index fdc5f609..2f26dca8 100644
--- a/include/chaiscript/language/chaiscript_engine.hpp
+++ b/include/chaiscript/language/chaiscript_engine.hpp
@@ -219,7 +219,7 @@ namespace chaiscript
                std::vector<std::string> t_modulepaths = std::vector<std::string>(),
                       std::vector<std::string> t_usepaths = std::vector<std::string>())
       : m_module_paths(std::move(t_modulepaths)), m_use_paths(std::move(t_usepaths)),
-        m_parser(std::make_unique<parser::ChaiScript_Parser<optimizer::Optimizer<optimizer::Block, optimizer::Constant_Fold, optimizer::Return, optimizer::For_Loop>>>())
+        m_parser(std::make_unique<parser::ChaiScript_Parser<optimizer::Optimizer<optimizer::Block, optimizer::Constant_Fold, optimizer::If, optimizer::Return, optimizer::For_Loop>>>())
     {
       if (m_module_paths.empty())
       {
@@ -244,7 +244,7 @@ namespace chaiscript
     ChaiScript( std::vector<std::string> t_modulepaths = std::vector<std::string>(),
                       std::vector<std::string> t_usepaths = std::vector<std::string>())
       : m_module_paths(std::move(t_modulepaths)), m_use_paths(std::move(t_usepaths)),
-        m_parser(std::make_unique<parser::ChaiScript_Parser<optimizer::Optimizer<optimizer::Block, optimizer::Constant_Fold, optimizer::Return, optimizer::For_Loop>>>())
+        m_parser(std::make_unique<parser::ChaiScript_Parser<optimizer::Optimizer<optimizer::Block, optimizer::Constant_Fold, optimizer::If, optimizer::Return, optimizer::For_Loop>>>())
     {
       if (m_module_paths.empty())
       {
diff --git a/include/chaiscript/language/chaiscript_eval.hpp b/include/chaiscript/language/chaiscript_eval.hpp
index e7263ba0..d02e328b 100644
--- a/include/chaiscript/language/chaiscript_eval.hpp
+++ b/include/chaiscript/language/chaiscript_eval.hpp
@@ -653,7 +653,7 @@ namespace chaiscript
 
     struct Ternary_Cond_AST_Node final : AST_Node {
         Ternary_Cond_AST_Node(std::string t_ast_node_text, Parse_Location t_loc, std::vector<AST_NodePtr> t_children) :
-          AST_Node(std::move(t_ast_node_text), AST_Node_Type::If, std::move(t_loc), std::move(t_children)) 
+          AST_Node(std::move(t_ast_node_text), AST_Node_Type::Ternary_Cond, std::move(t_loc), std::move(t_children)) 
           { assert(children.size() == 3); }
 
         Boxed_Value eval_internal(const chaiscript::detail::Dispatch_State &t_ss) const override {
diff --git a/include/chaiscript/language/chaiscript_optimizer.hpp b/include/chaiscript/language/chaiscript_optimizer.hpp
index 2e7064d2..370c3c49 100644
--- a/include/chaiscript/language/chaiscript_optimizer.hpp
+++ b/include/chaiscript/language/chaiscript_optimizer.hpp
@@ -107,6 +107,26 @@ namespace chaiscript {
       }
     };
 
+    struct If {
+      AST_NodePtr optimize(const AST_NodePtr &node) {
+        if ((node->identifier == AST_Node_Type::If || node->identifier == AST_Node_Type::Ternary_Cond)
+             && node->children.size() >= 2
+             && node->children[0]->identifier == AST_Node_Type::Constant)
+        {
+          const auto condition = std::dynamic_pointer_cast<eval::Constant_AST_Node>(node->children[0])->m_value;
+          if (condition.get_type_info().bare_equal_type_info(typeid(bool))) {
+            if (boxed_cast<bool>(condition)) {
+              return node->children[1];
+            } else if (node->children.size() == 3) {
+              return node->children[2];
+            }
+          }
+        }
+
+        return node;
+      }
+    };
+
     struct Constant_Fold {
       AST_NodePtr optimize(const AST_NodePtr &node) {