CFG Reader(First)
A. Fifth Edition
This is fifth?fourth? edition of my CFG Reader which stands for Context-Free-Grammar Reader. In this edition,
I finished the first set calculation and add a meta symbol---"{", "}".
What is First set?
Example: A -> a | b c | V
The variable A will have a first set of First(A) = {a, b, First(V)}.
program -> stmt-sequence
stmt-sequence -> stmt-sequence ; statement | statement
statement -> if-stmt | repeat-stmt | assign-stmt | read-stmt | write-stmt
if-stmt -> if boolean-exp then stmt-sequence end
| if boolean-exp then stmt-sequence else stmt-sequence end
repeat-stmt -> repeat stmt-sequence until boolean-exp
assign-stmt -> identifier := integer-exp
read-stmt -> read identifier
write-stmt -> write integer-exp
boolean-exp -> integer-exp comparison-op integer-exp
comparison-op -> < | =
integer-exp -> integer-exp addop term | term
addop -> + | -
term -> term mulop factor | factor
mulop -> * | /
factor -> ( integer-exp ) | number | identifier
This problem has a standard algorithm in text. So, will you just refer to the text if you are really interested in?
I highly suspect if there is anyone in my reader group would be interested in reading this or even want to have
any idea of "what is First" and how to calculate.
E.Further improvement
F.File listing
1. CFGReader.h
2. CFGReader.cpp
3. Grammar.h
4. Grammar.cpp
5. 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(); }
file name: Grammar.h
const int BufferLength=256; const int MaxTokenCount=80; const int MaxRHSCount=50; const int MaxRuleCount=200; const int MaxTokenLength=10; const int MaxProduction=10; struct Token { 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 { private: Token* 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); 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); void initialize(); 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); //void calculateNull(); void calculateFirst(); void calculateFollow(); void calculateNull(); bool Null(int tIndex); bool addFirstTerminal(int target, int source); bool addFirstNonTerminal(int target, int source); void calculateProperty(); public: Grammar(); void optimize(); void printRule(int index); void print(); void printToken(); void addRule(const char* str); void newRule(const char* str);//this is an internal method, not suitable for outside Token* operator[](int index); int addToken(const char* str, bool isTerminal=true); Token* createToken(const char* theName, bool isTerminal); int tokenIndex(const char* str); };
file name: Grammar.cpp
#include <iostream> #include "Grammar.h" using namespace std; const char* emptyStr="e"; const char* optionBegin="{"; const char* optionEnd="}"; int emptyIndex=-1; void Grammar::calculateProperty() { calculateNull(); calculateFirst(); calculateFollow(); } void Grammar::printToken() { for (int i=0; i<tokenCount; i++) { 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<<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); } void Grammar::calculateFollow() { } 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::addFirstTerminal(int target, int source) { //addFirst token[target]->first[token[target]->firstCount++]=source; //if it is epsilon if (token[source]->isNull) { //token[target]->isNull=true;//unless all is return true; } return false; } bool Grammar::addFirst(int target, int source) { //don't calculate meta symbol if (token[source]->isMeta) { return false; } //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; 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; } /* int theToken; bool added, tokenIsNull=false; //if the token epsilon is added, surely the token will be nullable if (token[source]->terminal) { return addFirstTerminal(int target, int source)); } else { added=false; for (int i=0; i<token[source]->count; i++) { int j=0; theToken=production[token[source]->production[i]][j]; do { if (token[theToken]->terminal) { //it means it is terminal epsilon if (!addFirstTerminal(target, theToken)) { break; } } else { //if it is nullable if (!addFirstNonTerminal(target, theToken)) { break; } } j++; theToken=production[token[source]->production[i]][j]; }while (theToken!=-1); //it must be the case that every choice is nullable if (theToken==-1) { token[target]->isNull=true; } } } return true; */ 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 (!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); } } 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 /* token[tIndex]->count--; for (i=ruleIndex; i<token[tIndex]->count; i++) { token[tIndex]->production[i]=token[tIndex]->production[i+1]; } */ 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 epsilonRule(++prodIndex); addRuleForToken(newIndex, prodIndex); } int Grammar::forgeToken(int index) { char str[MaxTokenLength+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); 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; } Token* Grammar::createToken(const char* theName, bool isTerminal) { Token* ptr=new Token; ptr->name=new char[strlen(theName)+1]; strcpy(ptr->name, theName); ptr->terminal=isTerminal; ptr->count=ptr->firstCount=ptr->followCount=0; ptr->isNull=false; if (strcmp(theName, optionBegin)==0||strcmp(theName, optionEnd)==0) { ptr->isMeta=true; } else { ptr->isMeta=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; 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; int curToken=production[token[tIndex]->production[ruleIndex]][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[token[tIndex]->production[ruleIndex]][j+1]!=-1) { production[prodIndex][pos+j]= production[token[tIndex]->production[ruleIndex]][j+1]; j++; } production[prodIndex][pos+j]=-1; } 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() { removeLeftRecursion(); commonLeftFactor(); calculateNull(); calculateFirst(); calculateFollow(); } 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); /* do { //left-shift productions production[token[tIndex]->production[index]][curPos]= production[token[tIndex]->production[index]][curPos+1]; curPos++; }while (production[token[tIndex]->production[index]][curPos]!=-1); */ //add epsilon /* if (curPos==1) { epsilonRule(token[tIndex]->production[index]); } */ //remove from token's production array the rule-index----"index" //shrink the array by one /* for (int i=index; i<token[tIndex]->count; i++) { token[tIndex]->production[i]=token[tIndex]->production[i+1]; } token[tIndex]->count--; */ removeRuleFromToken(tIndex, index); } void Grammar::removeRuleFromToken(int tIndex, int ruleIndex) { for (int i=ruleIndex; i<token[tIndex]->count; i++) { token[tIndex]->production[i]=token[tIndex]->production[i+1]; } token[tIndex]->count--; } 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++; } } } Token* 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: main.cpp (main)
#include <iostream> #include "CFGReader.h" using namespace std; int main() { CFGReader R; R.readFromFile("c:\\ruleTest.txt"); R.optimize(); R.print(); return 0; }
The input is something like following:
Please note that all tokens must be separated by space, including "|" and "->" and "{", "}" is meta symbol
equivalent to Kaleen star. The file is here.
M' -> program i ; Dl B Dl -> Dv Ml Ml -> Ml M | e M -> 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 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 Ln ; | e ; Lp -> e | Ln Ln -> L { , L } L -> i Ar Ar -> e | [ E ] E -> F { Oa F } Oa -> + | - F -> R { Om R } Om -> * | / R -> L | n | ( E ) | c C -> E Or E Or -> = | < | > | <= | >=
Here is the result:
M' ==> program i ; Dl B Dl ==> Dv Ml B ==> begin Sl end ; Dv ==> variables Vl | e Ml ==> e Ml0 M ==> module i ( Vl ) Dv B Vl ==> V Vl0 v ==> Il : T ; Il ==> i Il0 T ==> integer Ad ; | char Ad Ad ==> e | array [ n ] Sl ==> S Sl0 S ==> L := E ; | if C then S else S | loop Sl end ; | exit ; i ( Lp ) ; | begin Sl end ; | read Ln ; | write Ln ; | e ; L ==> i Ar E ==> F { Oa F } C ==> F { Oa F } Or E Lp ==> e | Ln Ln ==> i Ar { , L } Ar ==> e | [ E ] F ==> R { Om R } Oa ==> + | - R ==> i Ar | n | ( E ) | c Om ==> * | / Or ==> = | < | > | <= | >= Ml0 ==> module i ( Vl ) Dv B Ml0 | e Vl0 ==> V Vl0 | e Il0 ==> , i Il0 | e Sl0 ==> e | Sl name: M' isNull: false isTerminal: false first: [0]=program name: program isNull: false isTerminal: true first: [0]=program name: i isNull: false isTerminal: true first: [0]=i name: ; isNull: false isTerminal: true first: [0]=; name: Dl isNull: true isTerminal: false first: [0]=e,[1]=variables,[2]=module name: B isNull: false isTerminal: false first: [0]=begin name: Dv isNull: true isTerminal: false first: [0]=e,[1]=variables name: Ml isNull: true isTerminal: false first: [0]=e,[1]=module name: M isNull: false isTerminal: false first: [0]=module name: e isNull: true isTerminal: true first: [0]=e name: module isNull: false isTerminal: true first: [0]=module name: ( isNull: false isTerminal: true first: [0]=( name: Vl isNull: false isTerminal: false first: [0]=V name: ) isNull: false isTerminal: true first: [0]=) name: variables isNull: false isTerminal: true first: [0]=variables name: V isNull: false isTerminal: true first: [0]=V name: v isNull: false isTerminal: false first: [0]=i name: Il isNull: false isTerminal: false first: [0]=i name: : isNull: false isTerminal: true first: [0]=: name: T isNull: false isTerminal: false first: [0]=integer,[1]=char name: integer isNull: false isTerminal: true first: [0]=integer name: Ad isNull: true isTerminal: false first: [0]=e,[1]=array name: char isNull: false isTerminal: true first: [0]=char name: , isNull: false isTerminal: true first: [0]=, name: array isNull: false isTerminal: true first: [0]=array name: [ isNull: false isTerminal: true first: [0]=[ name: n isNull: false isTerminal: true first: [0]=n name: ] isNull: false isTerminal: true first: [0]=] name: begin isNull: false isTerminal: true first: [0]=begin name: Sl isNull: false isTerminal: false first: [0]=begin,[1]=;,[2]=i,[3]=if,[4]=loop,[5]=exit,[6]=read,[7]=write name: end isNull: false isTerminal: true first: [0]=end name: S isNull: false isTerminal: false first: [0]=begin,[1]=;,[2]=i,[3]=if,[4]=loop,[5]=exit,[6]=read,[7]=write name: L isNull: false isTerminal: false first: [0]=i name: := isNull: false isTerminal: true first: [0]=:= name: E isNull: false isTerminal: false first: [0]=i,[1]=n,[2]=(,[3]=c name: if isNull: false isTerminal: true first: [0]=if name: C isNull: false isTerminal: false first: [0]=i,[1]=n,[2]=(,[3]=c name: then isNull: false isTerminal: true first: [0]=then name: else isNull: false isTerminal: true first: [0]=else name: loop isNull: false isTerminal: true first: [0]=loop name: exit isNull: false isTerminal: true first: [0]=exit name: Lp isNull: true isTerminal: false first: [0]=e,[1]=i name: read isNull: false isTerminal: true first: [0]=read name: Ln isNull: false isTerminal: false first: [0]=i name: write isNull: false isTerminal: true first: [0]=write name: { isNull: false isTerminal: true first: name: } isNull: false isTerminal: true first: name: Ar isNull: true isTerminal: false first: [0]=e,[1]=[ name: F isNull: false isTerminal: false first: [0]=i,[1]=n,[2]=(,[3]=c name: Oa isNull: false isTerminal: false first: [0]=+,[1]=- name: + isNull: false isTerminal: true first: [0]=+ name: - isNull: false isTerminal: true first: [0]=- name: R isNull: false isTerminal: false first: [0]=i,[1]=n,[2]=(,[3]=c name: Om isNull: false isTerminal: false first: [0]=*,[1]=/ name: * isNull: false isTerminal: true first: [0]=* name: / isNull: false isTerminal: true first: [0]=/ name: c isNull: false isTerminal: true first: [0]=c name: Or isNull: false isTerminal: false first: [0]==,[1]=<,[2]=>,[3]=<=,[4]=>= name: = isNull: false isTerminal: true first: [0]== name: < isNull: false isTerminal: true first: [0]=< name: > isNull: false isTerminal: true first: [0]=> name: <= isNull: false isTerminal: true first: [0]=<= name: >= isNull: false isTerminal: true first: [0]=>= name: Ml0 isNull: true isTerminal: false first: [0]=module,[1]=e name: Vl0 isNull: true isTerminal: false first: [0]=V,[1]=e name: Il0 isNull: true isTerminal: false first: [0]=,,[1]=e name: Sl0 isNull: true isTerminal: false first: [0]=e,[1]=begin,[2]=;,[3]=i,[4]=if,[5]=loop,[6]=exit,[7]=read,[8]=write Press any key to continue