From 80974d3a2ef0e18b39215a2375ee623fbe0804db Mon Sep 17 00:00:00 2001
From: Robin Jadoul <robin.jadoul@gmail.com>
Date: Sat, 26 Nov 2016 14:11:20 +0100
Subject: [PATCH] Some work on general LR table generator

---
 include/Parsodus/lrtables/generator.h | 18 ++++++++++++++++-
 src/lrtables/generator.cpp            | 29 +++++++++++++++++++++++++--
 2 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/include/Parsodus/lrtables/generator.h b/include/Parsodus/lrtables/generator.h
index f49988d..423be1c 100644
--- a/include/Parsodus/lrtables/generator.h
+++ b/include/Parsodus/lrtables/generator.h
@@ -18,9 +18,10 @@ class Generator {
         /**
          * Constructor
          *
+         * @param start The start symbol for the grammar
          * @param g The grammar to translate
          */
-        Generator(const Grammar& g);
+        Generator(const std::string& start, const Grammar& g);
 
         /**
          * Generate an LRTable based on given grammar
@@ -35,6 +36,15 @@ class Generator {
          */
         virtual bool needsFollowSet() = 0;
 
+        /**
+         * Build the starting item to build all item sets from
+         *
+         * @param startrule The constructed extended starting rule
+         * @param eof The token used as end of file
+         */
+        virtual Item initial_item(Rule startrule, std::string eof) = 0;
+
+
         std::set<std::string> first(std::string s);
         std::set<std::string> follow(std::string s);
 
@@ -49,7 +59,13 @@ class Generator {
          */
         void buildFollow();
 
+        /**
+         * Compute the closure of an item set
+         */
+        std::set<Item> closure(const std::set<Item>& its);
+
         Grammar m_gram;
+        Rule m_startrule;
         std::map<std::string, std::set<std::string>> m_first;
         std::map<std::string, std::set<std::string>> m_follow;
 };
diff --git a/src/lrtables/generator.cpp b/src/lrtables/generator.cpp
index 665c0a5..8cf8a17 100644
--- a/src/lrtables/generator.cpp
+++ b/src/lrtables/generator.cpp
@@ -1,11 +1,20 @@
 #include "Parsodus/lrtables/generator.h"
 
+#include <queue>
+
 namespace pds {
 namespace lr
 {
+
+const std::string EXTENDED_START = "^";
+const std::string EOF_PLACEHOLDER = "$";
    
 template <typename Item>
-Generator<Item>::Generator(const Grammar& g) : m_gram(g), m_first(), m_follow() {
+Generator<Item>::Generator(const std::string& start, const Grammar& g) : m_gram(g), m_startrule(Rule{EXTENDED_START, {start}}), m_first(), m_follow() {
+    m_gram.terminals.insert(EOF_PLACEHOLDER); //End of file
+    m_gram.variables.insert(EXTENDED_START); //modified start rule
+    m_gram.rules[EXTENDED_START].insert(m_startrule);
+
     if (needsFollowSet()) {
         buildFirst();
         buildFollow();
@@ -15,6 +24,22 @@ Generator<Item>::Generator(const Grammar& g) : m_gram(g), m_first(), m_follow()
 template <typename Item>
 LRTable Generator<Item>::generate() {
     //TODO
+    LRTable table;
+    std::vector<std::set<Item>> itemsets;
+    itemsets.emplace_back(closure({initial_item(m_startrule, EOF_PLACEHOLDER)}));
+
+    std::queue<Item> itemqueue;
+    itemqueue.push(itemsets[0]);
+    while (!itemqueue.empty()) {
+        std::set<Item> cur = std::move(itemqueue.front());
+        itemqueue.pop();
+        
+        for (std::pair<std::string, std::set<Item>> succ : successors(cur)) {
+            //Add new itemset or merge
+        }
+    }
+
+    return table;
 }
 
 template <typename Item>
@@ -70,7 +95,7 @@ void Generator<Item>::buildFirst() {
 template <typename Item>
 void Generator<Item>::buildFollow() {
     //EOF follow the added start rule.
-    m_follow["^"].insert("$");
+    m_follow[EXTENDED_START].insert(EOF_PLACEHOLDER);
 
     bool changes = true;