From ccfa95a79f90548a3a8ed8090bdebff5cab93e65 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Ko=C4=8Di=C4=8Dka?= <martin.kocicka@gmail.com>
Date: Wed, 11 May 2016 10:52:12 +0200
Subject: [PATCH] added universal LR parsing algorithm
---
alib2algo/src/grammar/parsing/LRParser.cpp | 43 ++++++++++++++++++++++
alib2algo/src/grammar/parsing/LRParser.h | 4 ++
2 files changed, 47 insertions(+)
diff --git a/alib2algo/src/grammar/parsing/LRParser.cpp b/alib2algo/src/grammar/parsing/LRParser.cpp
index 11428be758..86a8246ffb 100644
--- a/alib2algo/src/grammar/parsing/LRParser.cpp
+++ b/alib2algo/src/grammar/parsing/LRParser.cpp
@@ -85,6 +85,49 @@ LR0Items LRParser::getNextStateItems ( LR0Items items, alphabet::Symbol symbol,
return getClosure ( transitionItems, originalGrammar );
}
+bool LRParser::parse ( LRActionTable actionTable, LRGotoTable gotoTable, automaton::State initialState, std::vector < alphabet::Symbol > input ) {
+ std::stack < automaton::State > states;
+ states.push ( initialState );
+
+ unsigned currentPosition = 0;
+ while ( true ) {
+ LRActionTable::iterator actionIterator = actionTable.find ( { states.top ( ), input[currentPosition] } );
+ if ( actionIterator == actionTable.end ( ) ) {
+ return false;
+ }
+
+ switch ( actionIterator->second.first ) {
+ case LRAction::Shift:
+ states.push ( actionIterator->second.second.get < automaton::State > ( ) );
+
+ ++currentPosition;
+ break;
+
+ case LRAction::Reduce: {
+ std::pair < alphabet::Symbol, std::vector < alphabet::Symbol > > reduceBy = actionIterator->second.second.get < std::pair < alphabet::Symbol, std::vector < alphabet::Symbol > > > ( );
+ for ( unsigned i = 0; i < reduceBy.second.size ( ); ++i ) {
+ states.pop ( );
+ }
+
+ LRGotoTable::iterator nextStateIterator = gotoTable.find ( { states.top ( ), reduceBy.first } );
+ if (nextStateIterator == gotoTable.end()) {
+ return false;
+ }
+
+ states.push ( nextStateIterator->second );
+
+ break;
+ }
+
+ case LRAction::Accept:
+ return true;
+ break;
+ }
+ }
+
+ return false;
+}
+
} /* namespace parsing */
} /* namespace grammar */
diff --git a/alib2algo/src/grammar/parsing/LRParser.h b/alib2algo/src/grammar/parsing/LRParser.h
index 561f69bf8d..2f1ad997f0 100644
--- a/alib2algo/src/grammar/parsing/LRParser.h
+++ b/alib2algo/src/grammar/parsing/LRParser.h
@@ -12,6 +12,8 @@
#include <grammar/ContextFree/CFG.h>
#include <grammar/parsing/LRParserTypes.h>
+#include <vector>
+
namespace grammar {
namespace parsing {
@@ -25,6 +27,8 @@ public:
static LR0Items getClosure ( LR0Items items, grammar::CFG originalGrammar );
static LR0Items getNextStateItems ( LR0Items items, alphabet::Symbol symbol, grammar::CFG originalGrammar );
+
+ static bool parse ( LRActionTable actionTable, LRGotoTable gotoTable, automaton::State initialState, std::vector < alphabet::Symbol > input );
};
} /* namespace parsing */
--
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