Edit #1: I think the problem is in my .l file. I don't think the rules are being treated as rules, and I'm not sure how to treat the terminals of the rules as strings.
My last project for a compilers class is to write a .l and a .y file for a simple SQL grammar. I have no experience with Flex or Yacc, so everything I have written I have pieced together. I only have a basic understanding of how these files work, so if you spot my problem can you also explain what that section of the file is supposed to do? I'm not even sure what the '%' symbols do.
Basically some rules just do not work when I try to parse something. Some rules hang and others reject when they should accept. I need to implement the following grammar:
start ::= expression expression ::= one-relation-expression | two-relation-expression one-relation-expression ::= renaming | restriction | projection renaming ::= term RENAME attribute AS attribute term ::= relation | ( expression ) restriction ::= term WHERE comparison projection ::= term | term [ attribute-commalist ] attribute-commalist ::= attribute | attribute , attribute-commalist two-relation-expression ::= projection binary-operation expression binary-operation ::= UNION | INTERSECT | MINUS | TIMES | JOIN | DIVIDEBY comparison ::= attribute compare number compare ::= < | > | <= | >= | = | <> number ::= val | val number val ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 attribute ::= CNO | CITY | CNAME | SNO | PNO | TQTY | SNAME | QUOTA | PNAME | COST | AVQTY | S# | STATUS | P# | COLOR | WEIGHT | QTY relation ::= S | P | SP | PRDCT | CUST | ORDERS Here is my .l file:
%{ #include <stdio.h> #include "p5.tab.h" %} binaryOperation UINION|INTERSECT|MINUS|TIMES|JOIN|DIVIDEBY compare <|>|<=|>=|=|<> attribute CNO|CITY|CNAME|SNO|PNO|TQTY|SNAME|QUOTA|PNAME|COST|AVQTY|S#|STATUS|P#|COLOR|WEIGHT|QTY relation S|P|SP|PRDCT|CUST|ORDERS %% [ \t\n]+ ; {binaryOperation} return binaryOperation; {compare} return compare; [0-9]+ return val; {attribute} return attribute; {relation} return relation; "RENAME" return RENAME; "AS" return AS; "WHERE" return WHERE; "(" return '('; ")" return ')'; "[" return '['; "]" return ']'; "," return ','; . {printf("REJECT\n"); exit(0);} %% Here is my .y file:
%{ #include <stdio.h> #include <stdlib.h> %} %token RENAME attribute AS relation WHERE binaryOperation compare val %% start: expression {printf("ACCEPT\n");} ; expression: oneRelationExpression | twoRelationExpression ; oneRelationExpression: renaming | restriction | projection ; renaming: term RENAME attribute AS attribute ; term: relation | '(' expression ')' ; restriction: term WHERE comparison ; projection: term | term '[' attributeCommalist ']' ; attributeCommalist: attribute | attribute ',' attributeCommalist ; twoRelationExpression: projection binaryOperation expression ; comparison: attribute compare number ; number: val | val number ; %% yyerror() { printf("REJECT\n"); exit(0); } main() { yyparse(); } yywrap() {} Here is my makefile:
p5: p5.tab.c lex.yy.c cc -o p5 p5.tab.c lex.yy.c p5.tab.c: p5.y bison -d p5.y lex.yy.c: p5.l flex p5.l This works:
S RENAME CNO AS CITY
These do not:
S
S WHERE CNO = 5
I have not tested everything, but I think there is a common problem for these issues.
