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LL(1)-Parser

LL(1)-Parser. p rogram -> ’ program’ ’ ( ’ identT ’ ) ’ varlist ’ begin ’ stlist ’ end ’ v arlist ->     type identlist ’ ; ’ t ype ->         ’ float ’ | ’ int ’ i dentlist ->   i dentT identelmlist i dentelmlist -> ’ , ’ identT identelmlist | e

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LL(1)-Parser

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  1. LL(1)-Parser program-> ’program’ ’(’identT ’)’ varlist ’begin’ stlist ’end’ varlist->     type identlist ’;’ type->         ’float’ | ’int’ identlist->   identT identelmlist identelmlist-> ’,’identT identelmlist | e stlist-> statement stlist | e statement->identT ’=’ exp ’;’ exp->identTbexp | ’(’ exp ’)’ bexp bexp-> ’+’ exp bexp | ’-’ exp bexp | e

  2. rpd.c #include <stdio.h> #include "rpd.h" #include "symtab.h" int nextT; void checkfor(int token) { if (token != nextT) { printf("Syntax Error \n "); exit(0); } else nextT = yylex(); }

  3. rpd.c void program() { checkfor(programT); checkfor('('); checkfor(identT); checkfor(')'); varlist(); checkfor(beginT); stlist(); checkfor(endT); printf("Compilering faerdig. Ingen fejl\n "); }

  4. LL(1)-Parser program-> ’program’ ’(’identT ’)’ varlist ’begin’ stlist ’end’ varlist->     type identlist ’;’ type->           ’float’ | ’int’ identlist->   identT identelmlist identelmlist-> ’,’identT identelmlist | e stlist-> statement stlist | e statement->identT ’=’ exp ’;’ exp->identTbexp | ’(’ exp ’)’ bexp bexp-> ’+’ exp bexp | ’-’ exp bexp | e

  5. rpd.c void type() { if (nextT == floatT) { checkfor(floatT); Ctype= floatT; } else { if (nextT == intT) { checkfor(intT); Ctype= intT; } else { printf("Syntax Error 'int' eller 'float' type forvendtet! \n "); exit(0); } } }

  6. LL(1)-Parser program-> ’program’ ’(’identT ’)’ varlist ’begin’ stlist ’end’ varlist->     type identlist ’;’ type->           ’float’ | ’int’ identlist->   identT identelmlist identelmlist-> ’,’identT identelmlist | e stlist-> statement stlist | e statement->identT ’=’ exp ’;’ exp->identTbexp | ’(’ exp ’)’ bexp bexp-> ’+’ exp bexp | ’-’ exp bexp | e

  7. rpd.c void identelmlist() { if (nextT == ',') { checkfor(','); checkfor(identT); identelmlist(); } }

  8. rpd.c int main() { init_sym(); nextT = yylex(); program(); }

  9. LL(1)-Parser statement->   identT '=' expA ';' expA->            term expBexpB->             termopr term expB | etermopr->   '+' | '-'term->             factor termBtermB->          factoropr factor termB | efactoropr-> '*' | '/'factor->          uopr expA |                       '(' expA ')' |                       realT |                        identTuopr->            '-' | e

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