CFG Reader(Parser)
A. Eighth Edition
This is eighth edition of my CFG Reader which stands for Context-Free-Grammar Reader. In this edition,
I finished the parser part by establishing a stack for parser and add the "scanner" into project.
The original grammar from teacher:
M -> program i ; Dl B
Dl -> Dv Ml
Ml -> Ml Mo | e
Mo -> module i ( Vl ) Dv B
Dv -> variables Vl | e
Vl -> Vl V | V
V -> Il : T ;
T -> integer Ad | char Ad
Il -> i | Il , i
L -> i Ar
Ad -> e | array [ n ]
B -> begin Sl end ;
Sl -> S | S Sl
S -> L := E ; | if C then S else S | loop Sl end ; | exit ; | i ( Lp ) ; | B |
read Ln ; | write Lo ; | e ;
Lp -> e | Ln
Ln -> L { , L }
Lo -> Lr { , Lr }
Lr -> i Ar | n | c
Ar -> e | [ E ]
E -> F { Oa F }
Oa -> + | -
F -> R { Om R }
Om -> * | /
R -> L | n | ( E ) | c
C -> E Or E
Or -> = | < | > | <= | >= | !=
The revised grammar by my class
Grammar's optimize method:
M ==> program i ; Dl B
Dl ==> Dv Ml
B ==> begin Sl end ;
Dv ==> variables Vl | e
Ml ==> e Ml0
Mo ==> module i ( Vl ) Dv B
Vl ==> V Vl0
V ==> Il : T ;
Il ==> i Il0
T ==> integer Ad | char Ad
Ad ==> e | array [ n ]
L ==> i Ar
Ar ==> e | [ E ]
Sl ==> S Sl0
S ==> i S0 | if C then S else S | loop Sl end ; | exit ; | begin Sl end ; |
read Ln ; | write
Lo ; | e ;
E ==> F M0
C ==> F M0 Or E
Lp ==> e | Ln
Ln ==> i Ar M1
Lo ==> Lr M2
Lr ==> i Ar | n | c
F ==> R M3
Oa ==> + | -
R ==> i Ar | n | ( E ) | c
Om ==> * | /
Or ==> = | < | > | <= | >= | !=
M0 ==> + F M0 | e | - F M0
M1 ==> , L M1 | e
M2 ==> , Lr M2 | e
M3 ==> * R M3 | e | / R M3
Ml0 ==> module i ( Vl ) Dv B Ml0 | e
Vl0 ==> i Il0 : T ; Vl0 | e
Il0 ==> , i Il0 | e
Sl0 ==> e | Sl
S0 ==> Ar := E ; | ( Lp ) ;
START ==> M $
The First and Follow set of all non-terminals:
name: M isNull: false isTerminal: false first: [0]=program follow: [0]=$ name: Dl isNull: true isTerminal: false first: [0]=e,[1]=variables,[2]=module follow: [0]=begin name: B isNull: false isTerminal: false first: [0]=begin follow: [0]=$,[1]=module,[2]=begin name: Dv isNull: true isTerminal: false first: [0]=variables,[1]=e follow: [0]=module,[1]=begin name: Ml isNull: true isTerminal: false first: [0]=e,[1]=module follow: [0]=begin name: Mo isNull: false isTerminal: false first: [0]=module follow: name: Vl isNull: false isTerminal: false first: [0]=i follow: [0]=module,[1]=begin,[2]=) name: V isNull: false isTerminal: false first: [0]=i follow: [0]=i,[1]=module,[2]=begin,[3]=) name: Il isNull: false isTerminal: false first: [0]=i follow: [0]=: name: T isNull: false isTerminal: false first: [0]=integer,[1]=char follow: [0]=; name: Ad isNull: true isTerminal: false first: [0]=e,[1]=array follow: [0]=; name: L isNull: false isTerminal: false first: [0]=i follow: [0]=,,[1]=;,[2]=) name: Ar isNull: true isTerminal: false first: [0]=e,[1]=[ follow: [0]=,,[1]=:=,[2]=;,[3]=),[4]=*,[5]=/,[6]=+,[7]=-,[8]=],[9]==,[10]=<,[11]=>,[12]=<=,[13]=> =,[14]=!=,[15]=then name: Sl isNull: false isTerminal: false first: [0]=i,[1]=if,[2]=loop,[3]=exit,[4]=begin,[5]=read,[6]=write,[7]=; follow: [0]=end name: S isNull: false isTerminal: false first: [0]=i,[1]=if,[2]=loop,[3]=exit,[4]=begin,[5]=read,[6]=write,[7]=; follow: [0]=i,[1]=if,[2]=loop,[3]=exit,[4]=begin,[5]=read,[6]=write,[7]=;,[8]=end,[9]=else name: E isNull: false isTerminal: false first: [0]=i,[1]=n,[2]=(,[3]=c follow: [0]=],[1]=),[2]=;,[3]=then name: C isNull: false isTerminal: false first: [0]=i,[1]=n,[2]=(,[3]=c follow: [0]=then name: Lp isNull: true isTerminal: false first: [0]=e,[1]=i follow: [0]=) name: Ln isNull: false isTerminal: false first: [0]=i follow: [0]=;,[1]=) name: Lo isNull: false isTerminal: false first: [0]=i,[1]=n,[2]=c follow: [0]=; name: Lr isNull: false isTerminal: false first: [0]=i,[1]=n,[2]=c follow: [0]=,,[1]=; name: F isNull: false isTerminal: false first: [0]=i,[1]=n,[2]=(,[3]=c follow: [0]=+,[1]=-,[2]=],[3]=),[4]=;,[5]==,[6]=<,[7]=>,[8]=<=,[9]=>=,[10]=!=,[11]=then name: Oa isNull: false isTerminal: false first: [0]=+,[1]=- follow: name: R isNull: false isTerminal: false first: [0]=i,[1]=n,[2]=(,[3]=c follow: [0]=*,[1]=/,[2]=+,[3]=-,[4]=],[5]=),[6]=;,[7]==,[8]=<,[9]=>,[10]=<=,[11]=>=,[12]=!=,[13]= then name: Om isNull: false isTerminal: false first: [0]=*,[1]=/ follow: name: Or isNull: false isTerminal: false first: [0]==,[1]=<,[2]=>,[3]=<=,[4]=>=,[5]=!= follow: [0]=i,[1]=n,[2]=(,[3]=c name: M0 isNull: true isTerminal: false first: [0]=+,[1]=e,[2]=- follow: [0]=],[1]=),[2]=;,[3]==,[4]=<,[5]=>,[6]=<=,[7]=>=,[8]=!=,[9]=then name: M1 isNull: true isTerminal: false first: [0]=,,[1]=e follow: [0]=;,[1]=) name: M2 isNull: true isTerminal: false first: [0]=,,[1]=e follow: [0]=; name: M3 isNull: true isTerminal: false first: [0]=*,[1]=e,[2]=/ follow: [0]=+,[1]=-,[2]=],[3]=),[4]=;,[5]==,[6]=<,[7]=>,[8]=<=,[9]=>=,[10]=!=,[11]=then name: Ml0 isNull: true isTerminal: false first: [0]=module,[1]=e follow: [0]=begin name: Vl0 isNull: true isTerminal: false first: [0]=i,[1]=e follow: [0]=module,[1]=begin,[2]=) name: Il0 isNull: true isTerminal: false first: [0]=,,[1]=e follow: [0]=: name: Sl0 isNull: true isTerminal: false first: [0]=e,[1]=i,[2]=if,[3]=loop,[4]=exit,[5]=begin,[6]=read,[7]=write,[8]=; follow: [0]=end name: S0 isNull: false isTerminal: false first: [0]=[,[1]=:=,[2]=( follow: [0]=i,[1]=if,[2]=loop,[3]=exit,[4]=begin,[5]=read,[6]=write,[7]=;,[8]=end,[9]=else name: START isNull: false isTerminal: false first: [0]=program follow: Press any key to continue
The idea is to follow to standard algorithm in text book. The debugging is a really hard job, considering the
error may arise from different part of program: grammar, scanner, parser or the source program itself!
E.Further improvement
F.File listing
1. CFGReader.h
2. CFGReader.cpp
3. Grammar.h
4. Grammar.cpp
5. parser.h
6. parser.cpp
7. scanner.h
8. scanner.cpp
9. errorno.h
10. errorNo.cpp
11. initialize.cpp
12. main.cpp (main)
file name: CFGReader.h
#include "Grammar.h" class CFGReader { private: char buffer[BufferLength]; FILE* stream; void newRule(const char* str); void readRule(); void addRule(const char* str); int addToken(const char* str, bool isTerminal=true); void printRule(int index); public: void readFromFile(const char* fileName); void optimize(); void print(); };
file name: CFGReader.cpp
#include <iostream> #include "CFGReader.h" using namespace std; Grammar grammar; const char* deliStr=" |\n"; //this would only remove the immediate left recursion //and should I expand it to remove all kinds of left-recursion? void CFGReader::readFromFile(const char* fileName) { if ((stream=fopen(fileName, "r"))==NULL) { cout<<"cannot open file "<<fileName<<endl; } else { readRule(); } } void CFGReader::readRule() { char* ptr=buffer; char* hold; int count=0; while (!feof(stream)) { count=0; fgets(buffer, BufferLength-1, stream); ptr=buffer; while ((ptr=strtok(ptr, " \n"))!=NULL) { if (strcmp(ptr, "|")!=0) { //test the first two token to see if old rule continues if (count==0) { hold=ptr; } if (count==1) { if (strcmp("->", ptr)==0) { /* curIndex=addToken(hold, false);//the index of cur token grammar[curIndex]->terminal=false; newRule(); */ newRule(hold); } else { addRule(hold); addRule(ptr); } } if (count>=2)//always add { addRule(ptr); } count++; } else { //this is an alternative production rule newRule(NULL); } ptr=NULL; } } } void CFGReader::newRule(const char* str) { grammar.newRule(str); } void CFGReader::optimize() { grammar.optimize(); } void CFGReader::addRule(const char* str) { grammar.addRule(str); } int CFGReader::addToken(const char* str, bool isTerminal) { return grammar.addToken(str, isTerminal); } void CFGReader::printRule(int index) { grammar.printRule(index); } void CFGReader::print() { grammar.print(); grammar.printToken(true); //grammar.buildTable(); //grammar.printTable(); //grammar.printAllRules(); }
file name: Grammar.h
#ifndef GRAMMAR_H #define GRAMMAR_H const int BufferLength=256; const int MaxTokenCount=80; const int MaxRHSCount=80; const int MaxRuleCount=200; const int MaxGrammarTokenLength=10; const int MaxProduction=10; const int TokenTypeCount=38; struct GrammarToken { //bool isMeta; bool terminal; bool isNull; char* name; int production[MaxProduction];//pointer to the production it gives int count; int firstCount; int followCount; int follow[MaxTokenCount]; int first[MaxTokenCount]; }; class Grammar { friend class Parser; private: GrammarToken* token[MaxTokenCount]; int tokenCount; int curIndex;//the index of current token int curPos;//the position at production rule //MaxRuleCount>=MaxVariableCount!!! int production[MaxRuleCount][MaxRHSCount]; int prodIndex;//pointing to current production, initialized to -1 int checkRecursion(int tIndex, int curToken); void grammarError(int theVar, int theToken, int rule1, int rule2); void addFirstIntoTable(int theVariable, int theFirst, int theRule); void addFollowIntoTable(int theVariable, int theRule); void addBeginEnd(); void addEpsilonForToken(int tIndex); bool addIntoFirst(int target, int source); bool addFirst(int target, int source); void shiftRule(int ruleIndex, bool Left2Right, int offset); void addAtEnd(int ruleIndex, int toAdd); void addRuleForToken(int tIndex, int ruleIndex); int copyRule(int source, int target);//return the position of -1 void replaceRule(int curToken, int ruleIndex); int findMetaSymbol(int& begin, int& end); void initialize(); void doReplaceMetaSymbol(int ruleIndex, int begin, int end); void removeRuleFromToken(int tIndex, int ruleIndex); void checkEpsilon(int ruleIndex); void removeImmediate(int tIndex, int ruleIndex); void doAddRule(int tIndex); void commonLeftFactor(); int findCommonFactor(int tokenIndex, int ruleIndex); void removeLeftRecursion(); void doCommonFactor(int tokenIndex, int ruleIndex, int index); int forgeToken(int index);//create a new variable void epsilonRule(int ruleIndex); bool isRedundant(int tIndex); void replaceMetaSymbol(); void calculateFirst(); void calculateFollow(); void calculateNull(); bool Null(int tIndex); bool addFollow(int target, int source); bool addIntoFollow(int target, int source); bool addFollowIntoFollow(int target, int source); void removeRedundant(); void removeToken(int tIndex); // void calculateProperty(); public: Grammar(); void buildTable(); void optimize(); void printRule(int index); void print(); void printTable(); void printAllRules(); void printToken(bool onlyVar=false); int variableCount(); int terminalCount(); void addRule(const char* str); void newRule(const char* str);//this is an internal method, not suitable for outside GrammarToken* operator[](int index); int addToken(const char* str, bool isTerminal=true); GrammarToken* createToken(const char* theName, bool isTerminal); int tokenIndex(const char* str); }; #endif
file name: Grammar.cpp
#include <iostream> #include "Grammar.h" using namespace std; const char* emptyStr="e"; const char* optionBegin="{"; const char* optionEnd="}"; const char* startStr="START"; const char* endStr="$"; int startSymbolIndex=-1; int stackBottomIndex=-1; int beginIndex=-1; int endIndex=-1; int emptyIndex=-1; int epsilonIndex=-1; int table[MaxTokenCount][MaxTokenCount]; char* terminalStr[TokenTypeCount]= { //GENERAL TYPE 5 "i", "n", "c", "COMMENT", "ERROR", //THE FOLLOWING ARE SYMBOL TYPE 18 "(", ")", ";", "+", "-", "*", "/", ":=", "<", ">", "=", "<=", ">=", "!=", "[", "]", ",", ":", //THE FOLLOWING ARE RESERVED TYPE 15 "begin", "end", "program", "variables","integer", "array", "char", "module", "if", "then", "else", "loop", "exit", "read", "write" }; //these are "hash-table-like" tables //this is exactly the opposite of below int token2type[MaxTokenCount]; //this is to translate tokenType in scanner to token-index of grammar int type2token[MaxTokenCount]; int matchTokens(const char* str) { for (int i=0; i<TokenTypeCount; i++) { if (strcmp(terminalStr[i], str)==0) { return i; } } return -1; } void Grammar::addEpsilonForToken(int tIndex) { if (epsilonIndex==-1) { epsilonRule(++prodIndex); addRuleForToken(tIndex, prodIndex); } else { addRuleForToken(tIndex, epsilonIndex); } } void Grammar::printTable() { /* cout<<" "; for (int i=0; i<tokenCount; i++) { cout<<"| "<<i; } cout<<endl; */ for (int r=0; r<tokenCount; r++) { if (token[r]->terminal) { continue; } cout<<token[r]->name<<":"; for (int c=0; c<tokenCount; c++) { if (table[r][c]!=-1) { cout<<token[c]->name<<"="<<table[r][c]<<","; } } cout<<endl; } } void Grammar::buildTable() { int typeIndex; for (int r=0; r<tokenCount; r++) { if (token[r]->terminal) { typeIndex=matchTokens(token[r]->name); if (typeIndex!=-1) { type2token[typeIndex]=r; token2type[r]=typeIndex; } } //initialize for (int c=0; c<MaxTokenCount; c++) { table[r][c]=-1; } } for (int i=0; i<tokenCount; i++) { if (token[i]->terminal) { continue; } for (int j=0; j<token[i]->count; j++) { int k=0, theRule=token[i]->production[j]; int theToken=production[theRule][k]; while (theToken!=-1) { addFirstIntoTable(i, theToken, theRule); if (!token[theToken]->isNull) { break; } k++; theToken=production[theRule][k]; } if (theToken==-1) { addFollowIntoTable(i, theRule); } } } } /* nCount=tCount=0; for (int r=0; r<MaxTokenCount; r++) { if (r<tokenCount) { if (token[r]->terminal) { typeIndex=matchTokens(token[r]->name); if (typeIndex!=-1) { type2token[typeIndex]=r; token2type[r]=typeIndex; } //I am making a invertable table!!! tArray[r]=tCount++; } else { //it is an invertable table!!! nArray[r]=nCount++; } } for (int c=0; c<MaxTokenCount; c++) { table[r][c]=-1; } } for (int i=0; i<tCount; i++) { for (int j=0; j<token[i]->count; j++) { int k=0, theRule=token[i]->production[j]; int theToken=production[theRule][k]; while (theToken!=-1) { addFirstIntoTable(theToken, j); if (!token[theToken]->isNull) { break; } k++; theToken=production[theRule][k]; } if (theToken==-1) { addFollowIntoTable(j); } } } } */ void Grammar::grammarError(int theVar, int theToken, int rule1, int rule2) { cout<<"error! the conflict of grammar at "; cout<<token[theVar]->name<<" for token of " <<token[theToken]->name <<" between rules of \n"; printRule(rule1); cout<<" and "; printRule(rule2); cout<<endl; } void Grammar::addFollowIntoTable(int theVariable, int theRule) { int temp; for (int i=0; i<token[theVariable]->followCount; i++) { temp=token[theVariable]->follow[i]; if (table[theVariable][temp]!=theRule) { if (table[theVariable][temp]!=-1) { grammarError(theVariable, temp, theRule, table[theVariable][temp]); } table[theVariable][temp]=theRule; } } } void Grammar::addFirstIntoTable(int theVariable, int theFirst, int theRule) { for (int i=0; i<token[theFirst]->firstCount; i++) { if (table[theVariable][token[theFirst]->first[i]]!=theRule) { if (table[theVariable][token[theFirst]->first[i]]!=-1) { grammarError(theVariable, token[theFirst]->first[i], theRule, table[theVariable][token[theFirst]->first[i]]); } table[theVariable][token[theFirst]->first[i]]=theRule; } } } int Grammar::variableCount() { int result=0; for (int i=0; i<tokenCount; i++) { if (!token[i]->terminal) { result++; } } return result; } int Grammar::terminalCount() { int result=0; for (int i=0; i<tokenCount; i++) { if (token[i]->terminal) { result++; } } return result; } //leave the rule unremoved!!! as I have no way to do it!!! void Grammar::removeToken(int tIndex) { delete[]token[tIndex]->name; delete token[tIndex]; tokenCount--; for (int i=tIndex; i<tokenCount; i++) { token[i]=token[i+1]; } } bool Grammar::isRedundant(int tIndex) { int k, theRule, theToken; for (int i=0; i<tokenCount; i++) { for (int j=0; j<token[i]->count; j++) { k=0; theRule=token[i]->production[j]; theToken=production[theRule][k]; while (theToken!=-1) { if (theToken==tIndex) { return false; } k++; theToken=production[theRule][k]; } } } return true; } //what is redundant? except the start variable //the non-terminal never appears in other rules! void Grammar::removeRedundant() { int tIndex=1; bool findNew=false; while (tIndex<tokenCount) { findNew=false; if (!token[tIndex]->terminal) { if (isRedundant(tIndex)) { removeToken(tIndex); findNew=true; } } if (findNew) { tIndex=1; } else { tIndex++; } } } void Grammar::printAllRules() { /* cout<<"\nnow print all rules\n"; for (int i=0; i<=prodIndex; i++) { cout<<"rule index "<<i<<": "; printRule(i); cout<<"\n"; } */ int sum=0; for (int i=0; i<tokenCount; i++) { if (!token[i]->terminal) { sum+=token[i]->count; } } cout<<" total rules is:"<<prodIndex+1; cout<<"\n and the sum is "<<sum<<endl; } void Grammar::addBeginEnd() { int begin=addToken(startStr, false); int end=addToken(endStr, true); prodIndex++; production[prodIndex][0]=0; production[prodIndex][1]=end; production[prodIndex][2]=-1; addRuleForToken(begin, prodIndex); startSymbolIndex=begin; stackBottomIndex=end; } /* void Grammar::calculateProperty() { calculateNull(); calculateFirst(); calculateFollow(); } */ void Grammar::printToken(bool onlyVar) { for (int i=0; i<tokenCount; i++) { if (onlyVar) { if (token[i]->terminal) { continue; } } cout<<"name: "<<token[i]->name<<endl; cout<<" isNull: "<<(token[i]->isNull?"true":"false")<<endl; cout<<" isTerminal: "<<(token[i]->terminal?"true":"false")<<endl; cout<<" first: "; for (int j=0; j<token[i]->firstCount; j++) { if (j!=0) { cout<<","; } cout<<"["<<j<<"]="<<token[token[i]->first[j]]->name; } cout<<"\n follow: "; for (j=0; j<token[i]->followCount; j++) { if (j!=0) { cout<<","; } cout<<"["<<j<<"]="<<token[token[i]->follow[j]]->name; } cout<<endl; } } //must use while loop to discover new set!!!!! void Grammar::calculateFirst() { int i; bool addNew; do { i=0; addNew=false; while (i<tokenCount) { //the terminal contains itself if (token[i]->terminal) { //addFirst don't judge if it is nullable!! addFirst(i, i); //token[i]->first[token[i]->firstCount++]=i; } else { //for all its rules for (int j=0; j<token[i]->count; j++) { int theToken, k=0; theToken=production[token[i]->production[j]][k]; //for each token in each rule do { //add non epsilon set if (addIntoFirst(i, theToken)) { addNew=true; } //if it is not null, means it is end if (!token[theToken]->isNull) { break; } //if it is nullable, continue k++; theToken=production[token[i]->production[j]][k]; }while (theToken!=-1); //it means all token in this rule is nullable, so if (theToken==-1) { //it is nullable //addEpsilonIntoFirst(i); addFirst(i, emptyIndex); } } } i++; } }while (addNew); } bool Grammar::addFollowIntoFollow(int target, int source) { bool addNew=false; for (int i=0; i<token[source]->followCount; i++) { if (addFollow(target, token[source]->follow[i])) { addNew=true; } } return addNew; } bool Grammar::addIntoFollow(int target, int source) { bool addNew=false; if (source==-1) { return false; } for (int i=0; i<token[source]->firstCount; i++) { //add non-epsilon if (!token[token[source]->first[i]]->isNull) { if (addFollow(target, token[source]->first[i])) { addNew=true; } } } return addNew; } void Grammar::calculateFollow() { int i; bool addNew, started; //token[startSymbolIndex]->follow[0]=stackBottomIndex; //token[startSymbolIndex]->followCount=1; do { i=0; addNew=false; while (i<tokenCount) { //the terminal contains itself if (!token[i]->terminal) { for (int tIndex=0; tIndex<tokenCount; tIndex++) { //for all its rules if (token[tIndex]->terminal) { continue; } //for each its rule for (int j=0; j<token[tIndex]->count; j++) { int theToken, k=0, theRule=token[tIndex]->production[j]; started=false; theToken=production[theRule][k]; //for each token in each rule do { //the token appears here if (started) { if (addIntoFollow(i, theToken)) { addNew=true; } if (!token[theToken]->isNull) { break; } } if (theToken==i) { started=true; //add non epsilon set, including -1 situation!!! } //if it is not null, means it is end //if it is nullable, continue k++; theToken=production[theRule][k]; }while (theToken!=-1); //it means all token in this rule is nullable, so if (started&&theToken==-1) { //it is nullable //add current variable Follow(j) into Follow(i); if (addFollowIntoFollow(i, tIndex)) { addNew=true; } } } } } i++; } }while (addNew); } void Grammar::addRuleForToken(int tIndex, int ruleIndex) { token[tIndex]->production[token[tIndex]->count++]=ruleIndex; } void Grammar::shiftRule(int ruleIndex, bool left2Right, int offset) { int end=0; while (production[ruleIndex][end]!=-1) { end++; } if (left2Right) { for (int i=end; i>=0; i--) { production[ruleIndex][i+offset]=production[ruleIndex][i]; } } else { for (int i=0; i<=end-offset; i++) { production[ruleIndex][i]=production[ruleIndex][i+offset]; } checkEpsilon(ruleIndex); } } void Grammar::checkEpsilon(int ruleIndex) { if (production[ruleIndex][0]==-1) { epsilonRule(ruleIndex); } } bool Grammar::addFollow(int target, int source) { //check if it is already there for (int i=0; i<token[target]->followCount; i++) { if (token[target]->follow[i]==source) { return false; } } //add at end token[target]->follow[token[target]->followCount++]=source; return true; } bool Grammar::addFirst(int target, int source) { //check if it is already there for (int i=0; i<token[target]->firstCount; i++) { if (token[target]->first[i]==source) { return false; } } //add at end token[target]->first[token[target]->firstCount++]=source; return true; } //add non epsilon into it. bool Grammar::addIntoFirst(int target, int source) { bool addNew=false; if (token[source]->terminal) { if (!token[source]->isNull) { return addFirst(target, source); } else { return false; } } for (int i=0; i<token[source]->firstCount; i++) { //add non epsilon if (!token[token[source]->first[i]]->isNull) { if (addFirst(target, token[source]->first[i])) { addNew=true; } } } return addNew; } bool Grammar::Null(int tIndex) { if (token[tIndex]->terminal) { return token[tIndex]->isNull; } for (int i=0; i<token[tIndex]->count; i++) { int j=0, theToken; theToken=production[token[tIndex]->production[i]][j]; do { if (theToken==tIndex||!Null(theToken)) { break; } j++; theToken=production[token[tIndex]->production[i]][j]; }while (theToken!=-1); if (theToken==-1) { return true; } } return false; } void Grammar::calculateNull() { for (int i=0; i<tokenCount; i++) { token[i]->isNull=Null(i); } } int Grammar::findMetaSymbol(int& begin, int& end) { int theRule, theToken, k; begin=end=-1; for (int i=0; i<tokenCount; i++) { for (int j=0; j<token[i]->count; j++) { k=0; theRule=token[i]->production[j]; theToken=production[theRule][k]; while (theToken!=-1) { if (theToken==beginIndex) { begin=k; } if (theToken==endIndex) { end=k; return theRule; } k++; theToken=production[theRule][k]; } } } return -1; } void Grammar::doReplaceMetaSymbol(int ruleIndex, int begin, int end) { int newTokenIndex=forgeToken(0), i=0; addRuleForToken(newTokenIndex, ++prodIndex); //token[newTokenIndex]->production[token[newTokenIndex]->count++]=++prodIndex; //token[newTokenIndex]->terminal=false; copyRule(ruleIndex, prodIndex); //shrink while (production[ruleIndex][i+end+1]!=-1) { production[ruleIndex][begin+i]=production[ruleIndex][i+end+1]; i++; } production[ruleIndex][begin+i]=-1; addAtEnd(ruleIndex, newTokenIndex); /* production[ruleIndex][begin]=newTokenIndex; production[ruleIndex][begin+1]=-1; */ shiftRule(prodIndex, false, begin+1); production[prodIndex][end-begin-1]=newTokenIndex; production[prodIndex][end-begin]=-1; addEpsilonForToken(newTokenIndex); /* if (epsilonIndex==-1) { eRuleIndex=++prodIndex; epsilonRule(eRuleIndex); } else { eRuleIndex=epsilonIndex; } addRuleForToken(newTokenIndex, eRuleIndex); */ } void Grammar::replaceMetaSymbol() { int begin, end, ruleIndex; while ((ruleIndex=findMetaSymbol(begin, end))!=-1) { doReplaceMetaSymbol(ruleIndex, begin, end); } /* for (int i=0; i<tokenCount; i++) { //if (token[i]->isMeta) if (i==beginIndex||i==endIndex) { removeToken(i); } } */ } void Grammar::addAtEnd(int ruleIndex, int toAdd) { int end=0; while (production[ruleIndex][end]!=-1) { end++; } production[ruleIndex][end++]=toAdd; production[ruleIndex][end]=-1; } //left-recursion: A -> A a | b | c //change to: A -> b A' | c A' // A' -> a A' | empty void Grammar::removeImmediate(int tIndex, int ruleIndex) { int newIndex=forgeToken(tIndex); int holdRuleIndex=token[tIndex]->production[ruleIndex]; //sequence matters! //change to: A -> b A' for (int i=0; i<token[tIndex]->count; i++) { if (i!=ruleIndex) { addAtEnd(token[tIndex]->production[i], newIndex); } } //shift removeRuleFromToken(tIndex, ruleIndex); addRuleForToken(newIndex, holdRuleIndex); //token[newIndex]->production[token[newIndex]->count++]=holdRuleIndex; shiftRule(holdRuleIndex, false, 1); addAtEnd(holdRuleIndex, newIndex); //add epsilon rule for new variable addEpsilonForToken(newIndex); /* epsilonRule(++prodIndex); addRuleForToken(newIndex, prodIndex); */ } int Grammar::forgeToken(int index) { char str[MaxGrammarTokenLength+2], ch; int len=strlen(token[index]->name); int temp=0, i=0; strcpy(str, token[index]->name); ch=str[len-1];//get last char of name if (ch>='0'&&ch<'9') { str[len-1]=ch+i+1; } else { str[len]='0'+i; str[len+1]='\0'; } //I won't bother to check repetitation of name while (tokenIndex(str)!=-1) { i++; if (ch>='0'&&ch<'9') { str[len-1]=ch+i+1; } else { str[len]='0'+i; str[len+1]='\0'; } } return addToken(str, false);//it is non-terminal for sure } int Grammar::copyRule(int source, int target) { int i=0; while (production[source][i]!=-1) { production[target][i]=production[source][i]; i++; } production[target][i]=-1; return i; } void Grammar::doAddRule(int tIndex) { token[tIndex]->production[token[tIndex]->count++]=++prodIndex; } void Grammar::addRule(const char* str) { int index; index=addToken(str); production[prodIndex][curPos++]=index; production[prodIndex][curPos]=-1;//set end } //if the token is already there, it return the index //otherwise, it add new node in token array int Grammar::addToken(const char* str, bool isTerminal) { int index; index=tokenIndex(str); if (index==-1) { index=tokenCount; } else { return index; } token[index]=createToken(str, isTerminal); if (strcmp(str, optionBegin)==0) { beginIndex=index; } if (strcmp(str, optionEnd)==0) { endIndex=index; } tokenCount++; if (strcmp(str, emptyStr)==0) { token[index]->isNull=true; emptyIndex=index; } return index; } void Grammar::newRule(const char* str) { if (str!=NULL) { curIndex=addToken(str, false); } //add one pointer token[curIndex]->production[token[curIndex]->count++]=++prodIndex; token[curIndex]->terminal=false; curPos=0;//reset to restart; } GrammarToken* Grammar::createToken(const char* theName, bool isTerminal) { GrammarToken* ptr=new GrammarToken; ptr->name=new char[strlen(theName)+1]; strcpy(ptr->name, theName); ptr->terminal=isTerminal; ptr->count=ptr->firstCount=ptr->followCount=0; ptr->isNull=false; return ptr; } int Grammar::tokenIndex(const char* str) { for (int i=0; i<tokenCount; i++) { if (strcmp(str, token[i]->name)==0) { return i; } } return -1; } int Grammar::checkRecursion(int tIndex, int curToken) { for (int i=0; i<token[curToken]->count; i++) { //token[tIndex]->production[i]=ruleIndex //production[ruleIndex][0] is the first left-recursion one if (production[token[curToken]->production[i]][0]<=curToken) { return i; } } return -1; } void Grammar::printRule(int index) { int nodeIndex=0; //cout<<" ~"<<index<<"~ "; while (production[index][nodeIndex]!=-1) { cout<<token[production[index][nodeIndex]]->name<<" "; nodeIndex++; } } void Grammar::initialize() { tokenCount=curIndex=curPos=0; prodIndex=-1;//in order to ++ blindly } Grammar::Grammar() { initialize(); } void Grammar::removeLeftRecursion() { int tIndex=0, curToken=0; bool newChange=false; while (tIndex<tokenCount) { if (!token[tIndex]->terminal) { for (int i=0; i<token[tIndex]->count; i++) { curToken=production[token[tIndex]->production[i]][0]; if (curToken<=tIndex&&!token[curToken]->terminal) { if (curToken!=tIndex) { replaceRule(tIndex, i); } else { removeImmediate(tIndex, i); } newChange=true; } } } //whenever there is some new findings, restart if (!newChange) { tIndex++; } else { tIndex=0; newChange=false; } } } void Grammar::replaceRule(int tIndex, int ruleIndex) { int pos, j, targetEnd, sourceEnd, curRule; curRule=token[tIndex]->production[ruleIndex]; int curToken=production[curRule][0]; for (int i=token[curToken]->count-1; i>=0; i--) { if (i>0) { doAddRule(tIndex); pos=copyRule(token[curToken]->production[i], prodIndex); j=0; while (production[curRule][j+1]!=-1) { production[prodIndex][pos+j]=production[curRule][j+1]; j++; } production[prodIndex][pos+j]=-1; //addRuleForToken(curToken, prodIndex); } else { targetEnd=sourceEnd=0; //curRule=token[tIndex]->production[ruleIndex]; while (true) { if (production[token[curToken]->production[0]][sourceEnd]==-1&& production[curRule][targetEnd]==-1) { break; } if (production[token[curToken]->production[0]][sourceEnd]!=-1) { sourceEnd++; } if (production[curRule][targetEnd]!=-1) { targetEnd++; } } j=targetEnd+sourceEnd-1; while (j>=0) { if (j>=sourceEnd) { production[curRule][j]=production[curRule][j-sourceEnd+1]; } else { production[curRule][j]=production[token[curToken]->production[0]][j]; } j--; } } } } //optimize sequence is first common-factor then remove left recursion //therefore I don't have to check if for same variable if there will be //more than one left-recursion void Grammar::optimize() { replaceMetaSymbol(); removeLeftRecursion(); commonLeftFactor(); //removeRedundant(); addBeginEnd(); calculateNull(); calculateFirst(); calculateFollow(); buildTable(); } int Grammar::findCommonFactor(int tIndex, int ruleIndex) { for (int i=ruleIndex+1; i<token[tIndex]->count; i++) { //if the two rule has the same first token if (production[token[tIndex]->production[ruleIndex]][0]== production[token[tIndex]->production[i]][0]) { /* //calculate if there is epsilon if (emptyIndex==-1) { emptyIndex=tokenIndex(emptyStr); } //if it is not epsilon if (production[token[tIndex]->production[i]][0]!=emptyIndex) { return i; } */ return i; } } return -1; } void Grammar::epsilonRule(int ruleIndex) { production[ruleIndex][0]=addToken(emptyStr); production[ruleIndex][1]=-1; } //sample: x -> Aa // x -> Ab //changed to: x -> Ax' //this is to change the old rule // x' -> b //this is to change the old rule // x' -> a //this is the new-added rule void Grammar::doCommonFactor(int tIndex, int ruleIndex, int index) { int newTokenIndex=forgeToken(tIndex);//create a new variable //move the second and after part to the new rule of new variable //doing: x' -> a //curPos=0; //prepare to add one new rule addRuleForToken(newTokenIndex, ++prodIndex); //token[newTokenIndex]->production[token[newTokenIndex]->count++]=++prodIndex; token[newTokenIndex]->terminal=false; copyRule(token[tIndex]->production[ruleIndex], prodIndex); shiftRule(prodIndex, false, 1); /* do { //do copying production[prodIndex][curPos]= production[token[tIndex]->production[ruleIndex]][curPos+1]; curPos++; //even the -1 at end is copied }while (production[token[tIndex]->production[ruleIndex]][curPos]!=-1); */ //in order to show an empty string, in case the string is "epsilon" /* if (curPos==1) { epsilonRule(prodIndex); } */ //replace x -> Aa with x -> Ax' production[token[tIndex]->production[ruleIndex]][1]=newTokenIndex; production[token[tIndex]->production[ruleIndex]][2]=-1;//end //doing: x' -> b //curPos=0; //prepare to add one new rule //pointing new token to where old rule lies addRuleForToken(newTokenIndex, token[tIndex]->production[index]); /* token[newTokenIndex]->production[token[newTokenIndex]->count++]= token[tIndex]->production[index]; */ shiftRule(token[tIndex]->production[index], false, 1); removeRuleFromToken(tIndex, index); } void Grammar::removeRuleFromToken(int tIndex, int ruleIndex) { token[tIndex]->count--; for (int i=ruleIndex; i<token[tIndex]->count; i++) { token[tIndex]->production[i]=token[tIndex]->production[i+1]; } } void Grammar::commonLeftFactor() { int index=-1, tIndex=0, ruleIndex=0; bool flag; //whenever a newrule is done, restart! while (tIndex<tokenCount) { ruleIndex=0; flag=false; while (ruleIndex<token[tIndex]->count) { index=findCommonFactor(tIndex, ruleIndex); if (index!=-1) { doCommonFactor(tIndex, ruleIndex, index); //restart flag=true; break; } else { ruleIndex++; } } if (flag) { tIndex=0; } else { tIndex++; } } } GrammarToken* Grammar::operator[](int index) { if (index>=0&&index<tokenCount) { return token[index]; } else { return NULL; } } void Grammar::print() { for (int i=0; i<tokenCount; i++) { if (!token[i]->terminal) { cout<<token[i]->name<<" ==> "; for (int j=0; j<token[i]->count; j++) { printRule(token[i]->production[j]); if (j!=token[i]->count-1) { cout<<" | "; } } cout<<"\n"; } } }
file name: parser.h
#include "grammar.h" const int MaxStackLength=50; class Parser { private: int stack[MaxStackLength]; bool push(int num); bool pop(int& num); int top; void initialize(); bool pushToken(int tIndex, int theToken); void prepare(); void pushRule(int theRule); public: Parser(); void parseFile(const char* fileName); };
file name: parser.cpp
#include <iostream> #include "parser.h" #include "scanner.h" #include "errorNo.h" using namespace std; Scanner scanner; extern Grammar grammar; const char* defaultListFile="c:\\nickListFile.txt"; extern int startSymbolIndex; extern int stackBottomIndex; extern int table[MaxTokenCount][MaxTokenCount]; extern int token2type[MaxTokenCount]; extern int type2token[MaxTokenCount]; extern int emptyIndex; bool Parser::pushToken(int tIndex, int theToken) { if (table[tIndex][theToken]!=-1) { cout<<grammar.token[tIndex]->name<<" => "; grammar.printRule(table[tIndex][theToken]); cout<<endl; pushRule(table[tIndex][theToken]); return true; } return false; } void Parser::pushRule(int theRule) { int len=0; while (grammar.production[theRule][len]!=-1) { len++; } for (int i=len-1; i>=0; i--) { if (!push(grammar.production[theRule][i])) { errorHandle(StackOverFlow); } } } void Parser::parseFile(const char*fileName) { int theToken, theVar; bool canPop=true; scanner.readFromFile(fileName, defaultListFile); prepare(); while (scanner.nextToken()) { if (!canPop) { errorHandle(UnexpectedEmptyStack); } if (scanner.token.type==COMMENTTYPE) { continue; } theToken=type2token[scanner.token.type]; while ((canPop=pop(theVar))==true) { if (grammar.token[theVar]->terminal) { if (theToken==theVar)//match { break; } else { if (theVar==emptyIndex) { continue; } errorHandle(IllegalGrammarToken); } } else { if (!pushToken(theVar, theToken)) { errorHandle(IllegalGrammarToken); } } } } if (pop(theVar)) { if (theVar!=stackBottomIndex) { errorHandle(NotEmptyStack); } /* if (theVar!=stackBottomIndex) { errorHandle(NotEmptyStack); } */ } } Parser::Parser() { initialize(); } void Parser::initialize() { top=0; } bool Parser::pop(int& num) { if (top==0) { return false; } num=stack[--top]; return true; } bool Parser::push(int num) { if (top==MaxStackLength-1) { return false; } stack[top++]=num; return true; } void Parser::prepare() { top=0; pushRule(grammar.token[startSymbolIndex]->production[0]); }
file name: scanner.h
/////////////////////////////////////////////////////////////////////////////////////////// //Program: SLang Scanner //Author: Qingzhe Huang //Date: Jan. 18, 2004 //FileName: scanner.h //Features: // 1. I want to improve efficiency of scanning, so I used table-driven method. // 2. I used enum to represent character of all ASCII---CharType---where "space, tab, // end of line, end of file are all considered to be White Space. // 3. All legal token is represented by enum TokenType. // 4. I defined a huge amount of TokenState which is basically the state of a DFA. As // I don't want to search reserved keyword with linear search or whatever, I have // many states for the reserved words. // 5. I deliberately make the sequence of first 38 TokenState elements exactly same as // all that of TokenType, so that each final state of DFA has a 1-1 correspondence with // type of token. // 6. I defined a struct of Token which may be used in future parser. // 7. I defined an errorNo variable to represent various errors. And a series error string // for displaying information. // 8. When class Scanner is created, it will initialize the big "state-charType" table. // 9. When readFromFile is called, it will first read one char in advance. // 10. When an error is encountered, the caller of Scanner should understand that no further // char is read in. So, stop calling "nextToken()". This is a bit controvercial, and I // plan to change it in next version. //////////////////////////////////////////////////////////////////////////////////////////// /*//////////////////////////////////////////////////////////////////////////// Program: SLang Scanner Author: Qingzhe Huang Date: Jan. 21, 2004 FileName: scanner.h Features: 1. I restructured the struct Token, to make it a union field in order to store int value for number. 2. I restructured the function "nextToken()" in order to give out correct line no. when error occurs. *//////////////////////////////////////////////////////////////////////////////// #ifndef SCANNER_H #define SCANNER_H #include <iostream> using namespace std; extern enum ErrorCode; const int TokenStateCount=138; const int CharTypeCount=72; const int MaxTokenLength=255; const int MaxNumberLength=12; enum CharType { //all small letters 26 SMALLA,SMALLB,SMALLC,SMALLD,SMALLE,SMALLF,SMALLG,SMALLH,SMALLI,SMALLJ,SMALLK,SMALLL, SMALLM,SMALLN,SMALLO,SMALLP,SMALLQ,SMALLR,SMALLS,SMALLT,SMALLU,SMALLV,SMALLW,SMALLX, SMALLY,SMALLZ, //all big letters 26 BIGA,BIGB,BIGC,BIGD,BIGE,BIGF,BIGG,BIGH,BIGI,BIGJ,BIGK,BIGL,BIGM,BIGN,BIGO,BIGP,BIGQ, BIGR,BIGS,BIGT,BIGU,BIGV,BIGW,BIGX,BIGY,BIGZ, //all digit 1 DIGIT, //all symbols 16 QUOTE, OPENPAR, CLOSEPAR, SEMICOLON,PLUS, MINUS, TIMES, SLASH, COLON, EQUAL,SMALLER,GREATER,EXCLAIM,OPENBRACKET, CLOSEBRACKET,COMMA, //space, tab, end of line are regarded as whitespace, 1 WHITESPACE, //UNDERSCORE IS A SPECIAL SYMBOL 1 UNDERSCORE, //all other ASCII is regarded as illegal 1 ILLEGAL }; //TOTAL 38, JUST 1-1 WITH THE FIRST 38 OF TOKENSTATE enum TokenType { //GENERAL TYPE 5 IDTYPE, NUMBERTYPE, CHARCONSTTYPE, COMMENTTYPE, ERRORTYPE, //THE FOLLOWING ARE SYMBOL TYPE 18 OPENPARTYPE, CLOSEPARTYPE, SEMICOLONTYPE, PLUSTYPE, MINUSTYPE, TIMESTYPE, SLASHTYPE, ASSIGNMENTTYPE, SMALLERTYPE, GREATERTYPE, EQUALTYPE, SMALLEREQUALTYPE, GREATEREQUALTYPE, NOTEQUALTYPE, OPENBRACKETTYPE, CLOSEBRACKETTYPE, COMMATYPE, COLONTYPE, //THE FOLLOWING ARE RESERVED TYPE 15 BEGINTYPE, ENDTYPE, PROGRAMTYPE, VARIABLESTYPE,INTEGERTYPE, ARRAYTYPE, CHARTYPE, MODULETYPE, IFTYPE, THENTYPE, ELSETYPE, LOOPTYPE, EXITTYPE, READTYPE, WRITETYPE }; //total 138 states enum TokenState { //THE FINAL STATE 38, in order to easy initialize "finalState", I put them in beginning //5 generals IDEND, NUMBEREND, CONSTCHAREND, COMMENTEND, ERROR, //18 symbols OPENPAREND, CLOSEPAREND, SEMICOLONEND, PLUSEND, MINUSEND, TIMESEND, SLASHEND, ASSIGNMENTEND, SMALLEREND, GREATEREND, EQUALEND, SMALLEREQUALEND, GREATEREQUALEND, NOTEQUALEND, OPENBRACKETEND, CLOSEBRACKETEND, COMMAEND, COLONEND, //15 reserved BEGINEND, ENDEND, PROGRAMEND, VARIABLESEND, INTEGEREND, ARRAYEND, CHAREND, MODULEEND, IFEND, THENEND, ELSEEND, LOOPEND, EXITEND, READEND, WRITEEND, //THE FOLLOWING ARE ALL NON-FINAL STATES //THE very FIRST CHAR 1 READY, //THE FOLLOWING ARE ALL RESERVED STATE //the first char 12 ARRAY1, BEGIN1, CHAR1, E1, I1, LOOP1, MODULE1, PROGRAM1, READ1, THEN1, VARIABLES1, WRITE1, //THE SECOND CHAR 15 ARRAY2, BEGIN2, CHAR2, ELSE2, END2, EXIT2, IF2, INTEGER2, LOOP2, MODULE2, PROGRAM2, READ2, THEN2, VARIABLES2, WRITE2, //THE THIRD CHAR 14 ARRAY3, BEGIN3, CHAR3, ELSE3, END3, EXIT3, INTEGER3, LOOP3, MODULE3, PROGRAM3, READ3, THEN3, VARIABLES3, WRITE3, //THE FOURTH CHAR 13 ARRAY4, BEGIN4, CHAR4, ELSE4, EXIT4, INTEGER4, LOOP4, MODULE4, PROGRAM4, READ4, THEN4, VARIABLES4, WRITE4, //THE FIFTH CHAR 7 ARRAY5, BEGIN5, INTEGER5, MODULE5, PROGRAM5, VARIABLES5, WRITE5, //THE SIXTH CHAR 4 INTEGER6, MODULE6, PROGRAM6, VARIABLES6, //THE SEVENTH CHAR 3 INTEGER7, PROGRAM7, VARIABLES7, //THE EIGHTH CHAR 1 VARIABLES8, //THE NINETH CHAR 1 VARIABLES9, //THESE ARE NON-RESERVED //THESE ARE GENERAL 9 IDBEGIN, IDUNDERSCORE, NUMBERBEGIN, CONSTCHARQUOTEBEGIN, CONSTCHARBEGIN, COMMENTSTARBEGIN, COMMENTBEGIN, COMMENTSTAREND, COMMENTSLASHBEGIN, //the SINGLE symbols 16 QUOTEBEGIN, OPENPARBEGIN, CLOSEPARBEGIN, SEMICOLONBEGIN, PLUSBEGIN, MINUSBEGIN, TIMESBEGIN, SLASHBEGIN, COLONBEGIN, SMALLERBEGIN, GREATERBEGIN, EQUALBEGIN, EXCLAIMBEGIN, OPENBRACKETBEGIN, CLOSEBRACKETBEGIN, COMMABEGIN, //MULTI SYMBOL 4 ASSIGNMENTBEGIN, SMALLEREQUALBEGIN, GREATEREQUALBEGIN, NOTEQUALBEGIN }; //extern ErrorCode errorNo; extern void errorHandle(ErrorCode errorNo); struct Token { TokenType type; union { char name[MaxTokenLength+1]; int number; }; }; class Scanner { private: int tokenCount; unsigned char ch; void printLineNo(); FILE* stream; bool nextChar(); void initialize(); bool resume(); public: Scanner(); static Token token; bool readFromFile(const char* fileName, const char* listFileName); const char* getToken(){return token.name;} bool nextToken(); void report(); }; void initialTokenState(); #endif
file name: scanner.cpp
/*//////////////////////////////////////////////////////////////////////////// Program: SLang Scanner Author: Qingzhe Huang Date: Jan. 21, 2004 FileName: scanner.cpp Features: 1. As Dr. Optrany said, the number should be stored as int or double whatever. 2. I restructured the function "nextToken()" in order to give out correct line no. when error occurs. *//////////////////////////////////////////////////////////////////////////////// #include <iostream> #include <fstream> #include "scanner.h" #include "errorNo.h" using namespace std; ofstream fList; //this will determine how many errors of maximum the scanner will tolerant const int MaxErrortolerant=10; //as integer usually have max 12 digit roughly int errorCount=0; int lineCount=1; //static memeber Token Scanner::token; const int TokenTypeCount=38; //extern void errorHandle(int errorNo); extern char* errorStr[ErrorCount]; //this is purely for displaying purpose char* tokenTypeStr[TokenTypeCount]= { //GENERAL TYPE 5 "ID", "NUMBER", "CHARACTER CONSTANT", "COMMENT", "ERROR", //THE FOLLOWING ARE SYMBOL TYPE 18 "(", ")", ";", "+", "-", "*", "/", ":=", "<", ">", "=", "<=", ">=", "!=", "[", "]", ",", ":", //THE FOLLOWING ARE RESERVED TYPE 15 "begin", "end", "program", "variables","integer", "array", "char", "module", "if", "then", "else", "loop", "exit", "read", "write" }; CharType charType[256]; TokenState tokenState[TokenStateCount][CharTypeCount]; //when error occurs, no message is immediately output, it is //postponed to next time, because when '\n' is read in, //lineCount is not incremented until token is decided. //Therefore, when a token is ended with '\n', the line no is not updated //until next round. So, we can keep the correct line no. for each token bool Scanner::nextToken() { TokenState state=READY; int digitCount=0; int value=0; int count=0;//to count the length of token char* ptr=token.name; bool isComment=false; do { //map ch to CharType reducing 256 ASCII to 73 CharTypes //the table for "state" and "CharType is 138x73, each entry is a //index for state. state=tokenState[state][charType[ch]]; if (state==NUMBERBEGIN) { digitCount++; if (digitCount>=MaxNumberLength) { errorHandle(ExceedNumberLimit); return resume(); } //to accumulate the value value*=10; value+=ch-'0'; } //because I put all final state in the first 38 positions if (state<38) { //This is a dirty trick! Because I make the "TokenType" 1-1 with //TokenState for the 38 finals. *ptr='\0'; token.type=(TokenType)(state); if (state==ERROR) { errorHandle(IllegalToken); //printLineNo(); return resume(); } tokenCount++; if (state==NUMBEREND) { token.number=value; } //printLineNo(); return true; } if (state==COMMENTBEGIN) { isComment=true; } if (count>=MaxTokenLength) { errorHandle(TokenTooLong); token.type=ERRORTYPE; //printLineNo(); return false; } //cout<<ch; if (!isComment&&state!=READY) { *ptr=ch; ptr++; count++; } //it is only at end to update line no. printLineNo(); }while (nextChar()); state=tokenState[state][charType[ch]]; //at this point, it is either in ready state, or error state if (state==ERROR) { token.type=(TokenType)(state); errorHandle(UnexpectedReachEOF); } //but in all case it means end of file, so return false return false; } bool Scanner::resume() { //the scanner will try to continue if error number is within 10 if (errorCount==MaxErrortolerant) { return false; } return nextChar(); } void Scanner::report() { fList<<"\ntotal number of tokens is "<<tokenCount; fList<<"\ntotal number of errors is "<<errorCount; } void Scanner::printLineNo() { if (ch=='\n') { fList<<++lineCount<<" "; } } Scanner::Scanner() { initialize(); } void Scanner::initialize() { errorCount=0; lineCount=1; tokenCount=0; initialTokenState(); } bool Scanner::readFromFile(const char* fileName, const char* listFileName) { if ((stream=fopen(fileName, "r"))==NULL) { errorHandle(CannotOpenFile); return false; } else { fList.open(listFileName); fList<<lineCount<<" "; //this is to prevent the empty file situation in which //you cannot even read one single char because my scanner need to read //one char ahead if (!nextChar()) { errorHandle(FileEmptyError); return false; } } return true; } bool Scanner::nextChar() { ch=fgetc(stream); fList<<ch; return ch!=255; }
file name: errorno.h
#ifndef ERRORNO_H #define ERRORNO_H extern char* errorStr[]; void errorHandle(int errorNo); const int ErrorCount=10; const int ScannerErrorCount=6; const int ParserErrorCount=4; //errors of scanner = 6 #define IllegalToken 0 #define TokenTooLong 1 #define UnexpectedReachEOF 2 #define FileEmptyError 3 #define CannotOpenFile 4 #define ExceedNumberLimit 5 //error of parser =4 #define UnexpectedEmptyStack 6 #define IllegalGrammarToken 7 #define NotEmptyStack 8 #define StackOverFlow 9 #endif
file name: errorno.cpp
#include <iostream> #include <fstream> #include "scanner.h" #include "errorNo.h" using namespace std; char* errorStr[ErrorCount]= { //these are scanner errors: "IllegalToken", "TokenTooLong", "UnexpectedReachEOF", "FileEmptyError", "CannotOpenFile", "ExceedNumberLimit", //these are parser errors "UnexpectedEmptyStack", "IllegalGrammarToken", "NotEmptyStack", "StackOverFlow" }; extern int errorCount; extern int lineCount; extern ofstream fList; //this is going to be improved in future as parser need to //call it, too. so, more parameter should be added? //No! the error no. itself specifies the error and it is //error handler to try to find necessary info to display. void errorHandle(int errorNo) { if (errorNo<ScannerErrorCount) { errorCount++; //the illegal token may be for various reason and I only suggest //a possible nearby place to spot the error occurs. fList<<"\nerror of "<<errorStr[errorNo]<<" occurred at line " <<lineCount<<" near token "<<Scanner::token.name<<endl; } else { if (errorNo<ScannerErrorCount+ParserErrorCount) { errorCount++; fList<<"\nerror of "<<errorStr[errorNo]<<" occurred at line " <<lineCount<<" near token "<<Scanner::token.name<<endl; exit(errorNo); } } }
file name: initialize.cpp
/*//////////////////////////////////////////////////////////////////////////// Program: SLang Scanner Author: Qingzhe Huang Date: Jan. 18, 2004 FileName: initialize.cpp Features: 1. This is purely mechnical job, you know to initialize a huge state table: 138x72 is really a boring, routine job. 2. For EOF, I want "ch" to be able to be an index in "CharType" array, so, it cannot be -1, but 255 for "unsigned char" which is declared in class Scanner. *//////////////////////////////////////////////////////////////////////////////// #include "scanner.h" extern enum CharType; extern enum TokenState; extern CharType charType[256]; extern TokenState tokenState[TokenStateCount][CharTypeCount]; void finalSymbolToken(TokenState state, TokenState endState); void finalReservedToken(TokenState state, TokenState endState); void initialCharType(); void setFinalTokenState(); void initialReserved(TokenState state); void setRange(TokenState state, CharType start, CharType end, TokenState target); void setState(TokenState state, TokenState targetState); void setDefaultState(); void setDefaultState() { //all states are by default error for (int i=0; i<TokenStateCount; i++) { setState((TokenState)i, ERROR); } //the default for all letters are IDBEGIN setRange(READY, SMALLA, BIGZ, IDBEGIN); //THIS IS another dirty trick, since I put all reserved states together //so you can initialize them together. for (i=ARRAY1; i<=VARIABLES9; i++) { initialReserved((TokenState)i); } setFinalTokenState(); } void setFinalTokenState() { //FOR ID finalReservedToken(IDBEGIN, IDEND); //for number finalReservedToken(NUMBERBEGIN, NUMBEREND); //THESE FOR RESERVED WORDS finalReservedToken(ARRAY5, ARRAYEND); finalReservedToken(BEGIN5, BEGINEND); finalReservedToken(CHAR4, CHAREND); finalReservedToken(ELSE4, ELSEEND); finalReservedToken(END3, ENDEND); finalReservedToken(EXIT4, EXITEND); finalReservedToken(IF2, IFEND); finalReservedToken(INTEGER7, INTEGEREND); finalReservedToken(LOOP4, LOOPEND); finalReservedToken(MODULE6, MODULEEND); finalReservedToken(PROGRAM7, PROGRAMEND); finalReservedToken(READ4, READEND); finalReservedToken(THEN4, THENEND); finalReservedToken(VARIABLES9, VARIABLESEND); finalReservedToken(WRITE5, WRITEEND); //THESE FOR SYMBOLS finalSymbolToken(OPENPARBEGIN, OPENPAREND); finalSymbolToken(CLOSEPARBEGIN, CLOSEPAREND); finalSymbolToken(SEMICOLONBEGIN, SEMICOLONEND); finalSymbolToken(PLUSBEGIN, PLUSEND); finalSymbolToken(MINUSBEGIN, MINUSEND); finalSymbolToken(TIMESBEGIN, TIMESEND); finalSymbolToken(SLASHBEGIN, SLASHEND); finalSymbolToken(ASSIGNMENTBEGIN, ASSIGNMENTEND); finalSymbolToken(SMALLERBEGIN, SMALLEREND); finalSymbolToken(GREATERBEGIN, GREATEREND); finalSymbolToken(EQUALBEGIN, EQUALEND); finalSymbolToken(SMALLEREQUALBEGIN, SMALLEREQUALEND); finalSymbolToken(GREATEREQUALBEGIN, GREATEREQUALEND); finalSymbolToken(NOTEQUALBEGIN, NOTEQUALEND); finalSymbolToken(OPENBRACKETBEGIN, OPENBRACKETEND); finalSymbolToken(CLOSEBRACKETBEGIN, CLOSEBRACKETEND); finalSymbolToken(COMMABEGIN, COMMAEND); finalSymbolToken(COLONBEGIN, COLONEND); //COMMENT finalSymbolToken(COMMENTSLASHBEGIN, COMMENTEND); //CONSTCHAR finalSymbolToken(CONSTCHARQUOTEBEGIN, CONSTCHAREND); } void initialTokenState() { //initialize all charType initialCharType(); //default is always error setDefaultState(); //loop tokenState[READY][WHITESPACE]=READY; //number tokenState[READY][DIGIT]=NUMBERBEGIN; tokenState[NUMBERBEGIN][DIGIT]=NUMBERBEGIN;//HOW LONG SHOULD NUMBER BE? //ID //setRange(READY, SMALLA, BIGZ, IDBEGIN); THIS IS IN DEFAULT setRange(IDBEGIN, SMALLA, DIGIT, IDBEGIN); tokenState[IDBEGIN][UNDERSCORE]=IDUNDERSCORE; setRange(IDUNDERSCORE, SMALLA, DIGIT, IDBEGIN); //reserved words //ARRAY1, BEGIN1, CHAR1, E1, I1, LOOP1, MODULE1, PROGRAM1, READ1, THEN1, WRITE1, //VARIABLES1, tokenState[READY][SMALLA]=ARRAY1; tokenState[READY][SMALLB]=BEGIN1; tokenState[READY][SMALLC]=CHAR1; tokenState[READY][SMALLE]=E1; tokenState[READY][SMALLI]=I1; tokenState[READY][SMALLL]=LOOP1; tokenState[READY][SMALLM]=MODULE1; tokenState[READY][SMALLP]=PROGRAM1; tokenState[READY][SMALLR]=READ1; tokenState[READY][SMALLT]=THEN1; tokenState[READY][SMALLV]=VARIABLES1; tokenState[READY][SMALLW]=WRITE1; /* RESERVED WORDS ARRAY2 */ tokenState[ARRAY1][SMALLR]=ARRAY2; //BEGIN2 tokenState[BEGIN1][SMALLE]=BEGIN2; //CHAR2 tokenState[CHAR1][SMALLH]=CHAR2; //ELSE2, tokenState[E1][SMALLL]=ELSE2; //EXIT2 tokenState[E1][SMALLX]=EXIT2; //END2 tokenState[E1][SMALLN]=END2; //IF2 tokenState[I1][SMALLF]=IF2; //INTEGER2 tokenState[I1][SMALLN]=INTEGER2; //LOOP2 tokenState[LOOP1][SMALLO]=LOOP2; //MODULE2 tokenState[MODULE1][SMALLO]=MODULE2; //PROGRAM2 tokenState[PROGRAM1][SMALLR]=PROGRAM2; //READ2 tokenState[READ1][SMALLE]=READ2; //THEN2 tokenState[THEN1][SMALLH]=THEN2; //VARIABLES2 tokenState[VARIABLES1][SMALLA]=VARIABLES2; //WRITE2 tokenState[WRITE1][SMALLR]=WRITE2; /* RESERVED WORDS ARRAY3 */ tokenState[ARRAY2][SMALLR]=ARRAY3; //BEGIN2 tokenState[BEGIN2][SMALLG]=BEGIN3; //CHAR2 tokenState[CHAR2][SMALLA]=CHAR3; //ELSE2, tokenState[ELSE2][SMALLS]=ELSE3; //END2 tokenState[END2][SMALLD]=END3; //EXIT2 tokenState[EXIT2][SMALLI]=EXIT3; //INTEGER2 tokenState[INTEGER2][SMALLT]=INTEGER3; //LOOP2 tokenState[LOOP2][SMALLO]=LOOP3; //MODULE2 tokenState[MODULE2][SMALLD]=MODULE3; //PROGRAM2 tokenState[PROGRAM2][SMALLO]=PROGRAM3; //READ2 tokenState[READ2][SMALLA]=READ3; //THEN2 tokenState[THEN2][SMALLE]=THEN3; //VARIABLES2 tokenState[VARIABLES2][SMALLR]=VARIABLES3; //WRITE2 tokenState[WRITE2][SMALLI]=WRITE3; /* RESERVED WORDS ARRAY3 */ tokenState[ARRAY3][SMALLA]=ARRAY4; //BEGIN2 tokenState[BEGIN3][SMALLI]=BEGIN4; //CHAR2 tokenState[CHAR3][SMALLR]=CHAR4; //ELSE2, tokenState[ELSE3][SMALLE]=ELSE4; //EXIT2 tokenState[EXIT3][SMALLT]=EXIT4; //INTEGER2 tokenState[INTEGER3][SMALLE]=INTEGER4; //LOOP2 tokenState[LOOP3][SMALLP]=LOOP4; //MODULE2 tokenState[MODULE3][SMALLU]=MODULE4; //PROGRAM2 tokenState[PROGRAM3][SMALLG]=PROGRAM4; //READ2 tokenState[READ3][SMALLD]=READ4; //THEN2 tokenState[THEN3][SMALLN]=THEN4; //VARIABLES2 tokenState[VARIABLES3][SMALLI]=VARIABLES4; //WRITE2 tokenState[WRITE3][SMALLT]=WRITE4; /* RESERVED WORDS ARRAY */ tokenState[ARRAY4][SMALLY]=ARRAY5; //BEGIN2 tokenState[BEGIN4][SMALLN]=BEGIN5; //INTEGER2 tokenState[INTEGER4][SMALLG]=INTEGER5; //MODULE2 tokenState[MODULE4][SMALLL]=MODULE5; //PROGRAM2 tokenState[PROGRAM4][SMALLR]=PROGRAM5; //VARIABLES2 tokenState[VARIABLES4][SMALLA]=VARIABLES5; //WRITE2 tokenState[WRITE4][SMALLE]=WRITE5; // RESERVED WORDS*/ //INTEGER2 tokenState[INTEGER5][SMALLE]=INTEGER6; //MODULE2 tokenState[MODULE5][SMALLE]=MODULE6; //PROGRAM2 tokenState[PROGRAM5][SMALLA]=PROGRAM6; //VARIABLES2 tokenState[VARIABLES5][SMALLB]=VARIABLES6; // RESERVED WORDS*/ //INTEGER2 tokenState[INTEGER6][SMALLR]=INTEGER7; //PROGRAM2 tokenState[PROGRAM6][SMALLM]=PROGRAM7; //VARIABLES2 tokenState[VARIABLES6][SMALLL]=VARIABLES7; // RESERVED WORDS*/ //VARIABLES2 tokenState[VARIABLES7][SMALLE]=VARIABLES8; //VARIABLES2 tokenState[VARIABLES8][SMALLS]=VARIABLES9; /* CONSTCHAR, UNDERSCOREBEGIN, ASSIGNMENTBEGIN, SMALLEREQUALBEGIN, GREATEREQUALBEGIN, NOTEQUAL, COMMENTBEGIN, IDUNDERSCORE,*/ //now is the symbols //QUOTEBEGIN, OPENPARBEGIN, CLOSEPARBEGIN, SEMICOLONBEGIN, //PLUSBEGIN, MINUSBEGIN, TIMESBEGIN, SLASHBEGIN, COLONBEGIN, SMALLERBEGIN, GREATERBEGIN, //EQUALBEGIN, EXCLAIMBEGIN, OPENBRACKETBEGIN, CLOSEBRACKETBEGIN, COMMABEGIN, //' tokenState[READY][QUOTE]=QUOTEBEGIN; //( tokenState[READY][OPENPAR]=OPENPARBEGIN; //) tokenState[READY][CLOSEPAR]=CLOSEPARBEGIN; //; tokenState[READY][SEMICOLON]=SEMICOLONBEGIN; //+ tokenState[READY][PLUS]=PLUSBEGIN; //- tokenState[READY][MINUS]=MINUSBEGIN; //* tokenState[READY][TIMES]=TIMESBEGIN; /// tokenState[READY][SLASH]=SLASHBEGIN; //: tokenState[READY][COLON]=COLONBEGIN; //< tokenState[READY][SMALLER]=SMALLERBEGIN; //> tokenState[READY][GREATER]=GREATERBEGIN; //= tokenState[READY][EQUAL]=EQUALBEGIN; //! tokenState[READY][EXCLAIM]=EXCLAIMBEGIN; //[ tokenState[READY][OPENBRACKET]=OPENBRACKETBEGIN; //] tokenState[READY][CLOSEBRACKET]=CLOSEBRACKETBEGIN; //, tokenState[READY][COMMA]=COMMABEGIN; //AFTER QUOTE IT CAN BE ANY CHARACTER, INCLUDING ILLEGAL CHAR setRange(QUOTEBEGIN, SMALLA, ILLEGAL, CONSTCHARBEGIN); //ANY OTHER STATE IS BY DEFAULT ERROR tokenState[CONSTCHARBEGIN][QUOTE]=CONSTCHARQUOTEBEGIN; //FOR /, DEFAULT IS SLASHEND, EXCEPT * WHICH IS COMMENTSTARBEGIN tokenState[SLASHBEGIN][TIMES]= COMMENTSTARBEGIN; //FOR :, DEFAULT IS COLONEND, EXCEPT FOR = WHICH IS ASSIGNMENTBEGIN tokenState[COLONBEGIN][EQUAL]= ASSIGNMENTBEGIN; //FOR <, DEFAULT IS SMALLEREND, EXCEPT FOR= WHICH IS SMALLEREQAULBEGIN tokenState[SMALLERBEGIN][EQUAL]=SMALLEREQUALBEGIN; //FOR >, DEFAULT IS GREATEREND, EXCEPT FOR= WHICH IS GREATEREQAULBEGIN tokenState[GREATERBEGIN][EQUAL]= GREATEREQUALBEGIN; tokenState[EXCLAIMBEGIN][EQUAL]= NOTEQUALBEGIN; //WITHIN COMMENT IT IS A LOOP, EXCEPT FOR * WHICH IS POSSIBLE FOR END OF COMMENT setRange(COMMENTSTARBEGIN, SMALLA, ILLEGAL, COMMENTBEGIN); tokenState[COMMENTSTARBEGIN][TIMES]=COMMENTSTAREND; setRange(COMMENTBEGIN, SMALLA, ILLEGAL, COMMENTBEGIN); tokenState[COMMENTBEGIN][TIMES]=COMMENTSTAREND; //FROM COMMENTSTARBEGIN, ALL IS BACK TO COMMENTBEGIN, EXCEPT / WHICH IS END OF COMMENT setRange(COMMENTSTAREND, SMALLA, ILLEGAL, COMMENTBEGIN); tokenState[COMMENTSTAREND][SLASH]=COMMENTSLASHBEGIN; // } void initialReserved(TokenState state) { setRange(state, SMALLA, DIGIT, IDBEGIN); finalReservedToken(state, IDEND); tokenState[state][UNDERSCORE]=IDUNDERSCORE;//a_ } void finalSymbolToken(TokenState state, TokenState endState) { for (int i=SMALLA; i<=WHITESPACE; i++) { tokenState[state][(CharType)i]=endState; } } void finalReservedToken(TokenState state, TokenState endState) { //all non-letter, non-digit is regarded to be delimeter for (int i=QUOTE; i<=WHITESPACE; i++) { tokenState[state][(CharType)i]=endState; } } //the default charType is ILLEGAL void initialCharType() { int chType; //the default charType is ILLEGAL for (int i=0; i<256; i++) { charType[i]=ILLEGAL; } //chType is SMALLA chType=SMALLA; for (i='a'; i<='z'; i++) { charType[i]=(CharType)(chType); chType++; } //chType is now BIGA chType=BIGA;//I don't want to rely on the trick. for (i='A'; i<='Z'; i++) { charType[i]=(CharType)(chType); chType++; } chType=DIGIT; for (i='0'; i<='9'; i++) { charType[i]=(CharType)(chType); } /* UNDERSCORE, QUOTE, OPENPAR, CLOSEPAR, SEMICOLON,PLUS, MINUS, TIMES, SLASH, COLON, EQUAL,SMALLER,GREATER,EXCLAIM,OPENBRACKET, CLOSEBRACKET,COMMA, SPACE,TAB, ENDLINE, ILLEGAL */ charType['_']=UNDERSCORE; charType['\'']=QUOTE; charType['(']=OPENPAR; charType[')']=CLOSEPAR; charType[';']=SEMICOLON; charType['+']=PLUS; charType['-']=MINUS; charType['*']=TIMES; charType['/']=SLASH; charType[':']=COLON; charType['=']=EQUAL; charType['<']=SMALLER; charType['>']=GREATER; charType['!']=EXCLAIM; charType['[']=OPENBRACKET; charType[']']=CLOSEBRACKET; charType[',']=COMMA; charType[' ']=WHITESPACE; charType['\t']=WHITESPACE; charType[10]=WHITESPACE; charType[13]=WHITESPACE; //pls note, since I changed the type of "ch" to be "unsigned char" //the EOF now is not -1, but 255 charType[255]=WHITESPACE;//IT IS A KIND OF DELIMETER } void setRange(TokenState state, CharType start, CharType end, TokenState target) { for (int i=start; i<=end; i++) { tokenState[state][i]=target; } } void setState(TokenState state, TokenState targetState) { for (int i=0; i<CharTypeCount; i++) { tokenState[state][i]=targetState; } }
file name: main.cpp (main)
#include <iostream> #include "CFGReader.h" #include "Parser.h" using namespace std; int main() { CFGReader R; Parser P; R.readFromFile("c:\\ruleTest.txt"); R.optimize(); //R.print(); cout<<"\n now begin parsing...\n"; P.parseFile("c:\\sourceTest.txt"); return 0; }
The input is something like following:
program average; /* a sample program. It calculates the average of integers, */ /* the first value gives the number of integers to read*/ variables n: integer; ave, total: integer; module sum(n, res :integer;) /* sums up n integers from input, puts the result into res*/ variables i: integer; val: integer array[100]; begin i:=i; res :=0; loop read val[i]; res:= res+ val[i]; i := i+1; if i>n then exit; else ; end; /* loop */ end;/* module sum*/ begin /* main program*/ read n; sum(n, total); ave:=(((total/n))); write 'a', 'v','e','r','a','g','e','='; write ave; end; /* of program*/
Here is the result:
now begin parsing... M => program i ; Dl B Dl => Dv Ml Dv => variables Vl Vl => V Vl0 V => Il : T ; Il => i Il0 Il0 => e T => integer Ad Ad => e Vl0 => i Il0 : T ; Vl0 Il0 => , i Il0 Il0 => e T => integer Ad Ad => e Vl0 => e Ml => e Ml0 Ml0 => module i ( Vl ) Dv B Ml0 Vl => V Vl0 V => Il : T ; Il => i Il0 Il0 => , i Il0 Il0 => e T => integer Ad Ad => e Vl0 => e Dv => variables Vl Vl => V Vl0 V => Il : T ; Il => i Il0 Il0 => e T => integer Ad Ad => e Vl0 => i Il0 : T ; Vl0 Il0 => e T => integer Ad Ad => array [ n ] Vl0 => e B => begin Sl end ; Sl => S Sl0 S => i S0 S0 => Ar := E ; Ar => e E => F M0 F => R M3 R => i Ar Ar => e M3 => e M0 => e Sl0 => Sl Sl => S Sl0 S => i S0 S0 => Ar := E ; Ar => e E => F M0 F => R M3 R => n M3 => e M0 => e Sl0 => Sl Sl => S Sl0 S => loop Sl end ; Sl => S Sl0 S => read Ln ; Ln => i Ar M1 Ar => [ E ] E => F M0 F => R M3 R => i Ar Ar => e M3 => e M0 => e M1 => e Sl0 => Sl Sl => S Sl0 S => i S0 S0 => Ar := E ; Ar => e E => F M0 F => R M3 R => i Ar Ar => e M3 => e M0 => + F M0 F => R M3 R => i Ar Ar => [ E ] E => F M0 F => R M3 R => i Ar Ar => e M3 => e M0 => e M3 => e M0 => e Sl0 => Sl Sl => S Sl0 S => i S0 S0 => Ar := E ; Ar => e E => F M0 F => R M3 R => i Ar Ar => e M3 => e M0 => + F M0 F => R M3 R => n M3 => e M0 => e Sl0 => Sl Sl => S Sl0 S => if C then S else S C => F M0 Or E F => R M3 R => i Ar Ar => e M3 => e M0 => e Or => > E => F M0 F => R M3 R => i Ar Ar => e M3 => e M0 => e S => exit ; S => e ; Sl0 => e Sl0 => e Ml0 => e B => begin Sl end ; Sl => S Sl0 S => read Ln ; Ln => i Ar M1 Ar => e M1 => e Sl0 => Sl Sl => S Sl0 S => i S0 S0 => ( Lp ) ; Lp => Ln Ln => i Ar M1 Ar => e M1 => , L M1 L => i Ar Ar => e M1 => e Sl0 => Sl Sl => S Sl0 S => i S0 S0 => Ar := E ; Ar => e E => F M0 F => R M3 R => ( E ) E => F M0 F => R M3 R => ( E ) E => F M0 F => R M3 R => ( E ) E => F M0 F => R M3 R => i Ar Ar => e M3 => / R M3 R => i Ar Ar => e M3 => e M0 => e M3 => e M0 => e M3 => e M0 => e M3 => e M0 => e Sl0 => Sl Sl => S Sl0 S => write Lo ; Lo => Lr M2 Lr => c M2 => , Lr M2 Lr => c M2 => , Lr M2 Lr => c M2 => , Lr M2 Lr => c M2 => , Lr M2 Lr => c M2 => , Lr M2 Lr => c M2 => , Lr M2 Lr => c M2 => , Lr M2 Lr => c M2 => e Sl0 => Sl Sl => S Sl0 S => write Lo ; Lo => Lr M2 Lr => i Ar Ar => e M2 => e Sl0 => e Press any key to continue