From 73d8cb372282908e9ed4d46096b95d52fc3afc21 Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <pair+mbrunsfeld@pivotallabs.com>
Date: Wed, 18 Dec 2013 08:25:50 -0800
Subject: [PATCH] Refactor parse table builder

---
 src/compiler/lr/parse_table_builder.cpp | 40 +++++++++++++++----------
 src/compiler/lr/parse_table_builder.h   |  4 ++-
 2 files changed, 27 insertions(+), 17 deletions(-)

diff --git a/src/compiler/lr/parse_table_builder.cpp b/src/compiler/lr/parse_table_builder.cpp
index c7734276..6c5fe815 100644
--- a/src/compiler/lr/parse_table_builder.cpp
+++ b/src/compiler/lr/parse_table_builder.cpp
@@ -17,7 +17,8 @@ namespace tree_sitter {
         ParseTableBuilder::ParseTableBuilder(const Grammar &grammar) :
             grammar(grammar),
             table(ParseTable(grammar.rule_names())),
-            state_indices(unordered_map<const ItemSet, size_t>()) {};
+            state_indices(unordered_map<const ItemSet, size_t>())
+            {};
 
         void ParseTableBuilder::build() {
             auto item = Item(ParseTable::START, rules::sym(grammar.start_rule_name), 0);
@@ -31,24 +32,31 @@ namespace tree_sitter {
                 state_index = table.add_state();
                 state_indices[item_set] = state_index;
 
-                for (auto transition : item_set.sym_transitions(grammar)) {
-                    rules::sym_ptr symbol = static_pointer_cast<const rules::Symbol>(transition.first);
-                    size_t new_state_index = add_item_set(*transition.second);
-                    table.add_action(state_index, symbol->name, ParseAction::Shift(new_state_index));
-                }
-                
-                for (Item item : item_set) {
-                    if (item.is_done()) {
-                        if (item.rule_name == ParseTable::START) {
-                            table.add_action(state_index, ParseTable::END_OF_INPUT, ParseAction::Accept());
-                        } else {
-                            for (string rule_name : table.symbol_names)
-                                table.add_action(state_index, rule_name, ParseAction::Reduce(item.rule_name, item.consumed_sym_count));
-                        }
+                add_shift_actions(item_set, state_index);
+                add_reduce_actions(item_set, state_index);
+            }
+            return state_index;
+        }
+        
+        void ParseTableBuilder::add_shift_actions(const ItemSet &item_set, size_t state_index) {
+            for (auto transition : item_set.sym_transitions(grammar)) {
+                rules::sym_ptr symbol = static_pointer_cast<const rules::Symbol>(transition.first);
+                size_t new_state_index = add_item_set(*transition.second);
+                table.add_action(state_index, symbol->name, ParseAction::Shift(new_state_index));
+            }
+        }
+        
+        void ParseTableBuilder::add_reduce_actions(const ItemSet &item_set, size_t state_index) {
+            for (Item item : item_set) {
+                if (item.is_done()) {
+                    if (item.rule_name == ParseTable::START) {
+                        table.add_action(state_index, ParseTable::END_OF_INPUT, ParseAction::Accept());
+                    } else {
+                        for (string rule_name : table.symbol_names)
+                            table.add_action(state_index, rule_name, ParseAction::Reduce(item.rule_name, item.consumed_sym_count));
                     }
                 }
             }
-            return state_index;
         }
         
         long ParseTableBuilder::state_index_for_item_set(const ItemSet &item_set) const {
diff --git a/src/compiler/lr/parse_table_builder.h b/src/compiler/lr/parse_table_builder.h
index 88bca265..9a58752d 100644
--- a/src/compiler/lr/parse_table_builder.h
+++ b/src/compiler/lr/parse_table_builder.h
@@ -13,8 +13,10 @@ namespace tree_sitter {
             ParseTable table;
             std::unordered_map<const ItemSet, size_t> state_indices;
 
-            size_t add_item_set(const ItemSet &item_set);
             long state_index_for_item_set(const ItemSet &item_set) const;
+            void add_shift_actions(const ItemSet &item_set, size_t state_index);
+            void add_reduce_actions(const ItemSet &item_set, size_t state_index);
+            size_t add_item_set(const ItemSet &item_set);
         public:
             ParseTableBuilder(const Grammar &grammar);
             static ParseTable build_table(const Grammar &grammar);