From 85d5142c600d4e7f43d762b97734487c0d6b7044 Mon Sep 17 00:00:00 2001
From: Robin Jadoul <robin.jadoul@gmail.com>
Date: Sun, 1 Jan 2017 12:44:40 +0100
Subject: [PATCH] Parser template implementation

---
 templates/c++/lr.h | 74 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 70 insertions(+), 4 deletions(-)

diff --git a/templates/c++/lr.h b/templates/c++/lr.h
index f0a7075..d58d1c6 100644
--- a/templates/c++/lr.h
+++ b/templates/c++/lr.h
@@ -2,7 +2,9 @@
 #ifndef PARSODUS_PARSER_{{name}}_H
 #define PARSODUS_PARSER_{{name}}_H
 
+#include <cassert>
 #include <deque>
+#include <stack>
 
 template <typename Value>
 class {{name}} {
@@ -48,15 +50,25 @@ class {{name}} {
          * Apply a reduction (a grammar rule in reverse)
          */
         {{#rules}}
-        {{#name}}virtual Value reduce_{{name}}(const std::deque<Token>& subparts) = 0;{{/name}}
-        {{^name}}virtual Value reduce_{{index}}(const std::deque<Token>& subparts) = 0;{{/name}}
+        {{#name}}virtual Token reduce_{{name}}(std::deque<Token> subparts) = 0;{{/name}}
+        {{^name}}virtual Token reduce_{{index}}(std::deque<Token> subparts) = 0;{{/name}}
         {{/rules}}
 
     private:
 };
 
+#define TABLE {{name}}___Table___{{name}}
+#define REDUCE_COUNT {{name}}___Num_Reduces___{{name}}
 // Not a static member because the table should not be replicated for different instantiations of the parser
-extern const std::uint64_t {{name}}___Table[%(num_states)][%(num_symbols)];
+extern const std::uint64_t TABLE[%(num_states)][%(num_symbols)];
+extern const unsigned char REDUCE_COUNT[%(num_rules)];
+
+enum Action {
+    ERROR = 0,
+    SHIFT = 1,
+    REDUCE = 2,
+    ACCEPT = 3
+};
 
 
 /***************************
@@ -64,7 +76,61 @@ extern const std::uint64_t {{name}}___Table[%(num_states)][%(num_symbols)];
 ***************************/
 template <typename Value>
 Value {{name}}::parse() {
-    //TODO
+    std::stack<Token> valueStack;
+    std::stack<std::uint64_t> stateStack;
+
+    stateStack.push(0);
+    Token tok = lex();
+
+    while (true) {
+        std::uint64_t act = TABLE[stateStack.top()][tok.symbol];
+
+       switch (act & 0x3) {
+            case ERROR:
+                //TODO: error handling
+                assert(false);
+                break;
+            case SHIFT:
+                valueStack.emplace(std::move(tok));
+                stateStack.push(act >> 2);
+                tok = lex();
+                break;
+            case REDUCE:
+                {
+                    std::uint64_t rule = act >> 2;
+                    std::deque<Token> dq;
+                    for (decltype(RECUDE_COUNT[rule]) i = 0; i < REDUCE_COUNT[rule]; i++) {
+                        dq.emplace_front(std::move(valueStack.top()));
+                        valueStack.pop();
+                        stateStack.pop();
+                    }
+
+                    switch (rule) {
+                        {{#rules}}
+                        case {{index}}:
+                            {{#name}}valueStack.emplace(reduce_{{name}}(std::move(dq))){{/name}}
+                            {{^name}}valueStack.emplace(reduce{{index}}(std::move(dq))){{/name}}
+                            break;
+                        {{/rules}}
+                        default:
+                            assert(false); //There should be no such rule
+                            break;
+                    }
+
+                    stateStack.push(TABLE[stateStack.top()][valueStack.top().symbol] >> 2);
+                }
+                break;
+            case ACCEPT:
+                assert(stateStack.size() == 2);
+                assert(valueStack.size() == 1);
+                return valueStack.top().value;
+            default:
+                //IMPOSSIBLE
+                break;
+        }
+    }
 }
+#undef REDUCE_COUNT
+#undef TABLE
 
 #endif /* PARSODUS_PARSER_{{name}}_H */