Edward Venator
EECS 337 HW3 Assignment
A syntactical analyzer created using bison and the C programming language.
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Intro
This program is a lexical and syntactical analyzer designed to parse the code found on the bottom of page 
986 of the text.
The lexical analyzer runs through a file of code, specified by a command line argument,
and performs lexical analysis, adding symbols to a symbol table, implemented as a linked 
list.
The syntactical analyzer adds type information for each symbol in the symbol table and 
prints out the rules being used as it constructs a parse tree. In addition, the syntactical
analyzer implements rudimentary error handling, as described in assumptions.txt.
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Lexemes
The Lexical Analyzer recognizes the following lexemes:
* Whitespace - perform no action
* Comment - perform no action. Recognizes singal line (//Comment) and block (/*Comment*/) style comments
* if - yylval=NULL; prints "if"; returns IF token
* else - yylval=NULL; prints "else"; returns ELSE token
* while - yylval=NULL; prints "while"; returns WHILE token
* do - yylval=NULL; prints "do"; returns DO token
* break - yylval=NULL; prints "break"; returns BREAK token
* basic - yylval=pointer to int_var or float_var as appropriate; prints "basic"; returns BASIC token
* true - yylval=pointer to true_var; prints "true"; returns BOOL token
* false - yylval=pointer to false_var; prints "false"; returns BOOL token
* id - yylval=pointer to entry in symbol table; prints "id"; returns ID token
* num - yylval=void * pointer to integer; prints "num"; returns NUM token
* real - yylval=void * pointer to float; prints "real"; returns REAL token
* <= - yylval=NULL; prints "<="; returns LE token
* < - yylval=NULL; prints "<"; returns LT token
* >= - yylval=NULL; prints ">="; returns GE token
* > - yylval=NULL; prints ">"; returns GT token
* == - yylval=NULL; prints "=="; returns EQUALTO token
* != - yylval=NULL; prints "!="; returns NOTEQUAL token
* { - yylval=NULL; prints "{"; returns OPENBRACKET token
* } - yylval=NULL; prints "}"; returns CLOSEBRACKET token
* ( - yylval=NULL; prints "("; returns OPENPAREN token
* ) - yylval=NULL; prints ")"; returns CLOSEPAREN token
* && - yylval=NULL; prints "&&"; returns AND token
* || - yylval=NULL; prints "||"; returns OR token
* ; - yylval=NULL; prints ";"; returns SEMI token
* + - yylval=NULL; prints "+"; returns PLUS
* - - yylval=NULL; prints "-"; returns MINUS token
* * - yylval=NULL; prints "*"; returns MULTI token
* / - yylval=NULL; prints "/"; returns DIV token
* ! - yylval=NULL; prints "!"; returns NOT token
* = - yylval=NULL; prints "="; returns EQUALS token
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The Symbol Table
The symbol table, contained in symbol.c, is implemented as a linked list with the 
following functions:
list_head_t *list_init(int (*cmp)(const void *, const void *))
*allocates memory for a list head, returns a pointer to the list head
list_entry_t* listinsert(list_head_t *head, void *key, void *value)
*adds a list entry key=>value to list with head head, returns a pointer to this entry
list_entry_t *list_search_entry(list_head_t *head, void *key)
*searches list with head head for an entry with key key and returns a pointer to the first
 entry found
void *list_search(list_head_t *head, void *key)
*searches list with head head for an entry with key key and returns a pointer to the value
 of this entry
*not used in this assignment
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Grammar Rules
prgrm->block
block->'{' decls stmts '}'
decls->/*empty*/
	|	decls decl
decl->type ID ';'								Add a type designation to the symbol table.
type->type [ NUM ]								Add a dimension to the type designation for the id.
	|	BASIC
stmts->/*empty*/
	|	stmts stmt
stmt->loc = bool ';'
	|	"if" '(' bool ')' stmt
	|	"if" '(' bool ')' stmt "else" stmt
	|	"while" '(' bool ')' stmt
	|	"do" stmt "while" '(' bool ')' ';'
	|	"break" ';'
	|	block
	|	error ";"								If an error is encountered, increment error counter and skip to after next semicolon.
loc->loc '[' bool ']'
	|	ID
bool->bool "||" join
	|	join
join->join "&&" equality
	|	equality
equality->equality "==" rel
	|	equality "!=" rel
	|	rel
rel->	expr '<' expr
	|	expr "<=" expr
	|	expr ">=" expr
	|	expr '>' expr
	|	expr
expr->	expr '+' term
	|	expr '-' term
	|	term
term->	term '*' unary
	|	term '/' unary
	|	unary
unary->'!' unary
	|	'-' unary
	|	factor
factor->'(' bool ')'
	|	loc
	|	NUM
	|	REAL
	|	BOOL
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lex.h
A header file for lex.yy.c (generated by flex from lex.l). Contains definitions for all 
auxiliary functions in lex.l.
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lex.l
This is the lex file containing the lexical analyzer. It contains no main method.
To compile:
flex lex.l
Compiling this file creates lex.yy.c, which is dependent on lex.h.
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yacc.y
This is the yacc file containing the parser. It contains a main method which opens the file 
with a name passed by command line argument, then runs yyparse() on this file, and prints
every rule it executes. At the end of execution, it prints the symbol table, including type
entries.
To Compile:
bison yacc.y
Compiling this file creates yacc.tab.c, which is dependent on lex.c. This file does not need 
to be editted and can be compiled immediately after creation.
To Compile:
gcc yac.tab.c -o yacc -ll -ly
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Running yacc
To run yacc, open a command line shell, cd to the appropriate directory then enter the 
command:
./yacc <filepath>
where <filepath> is the file you wish yacc to analyze. The file "test" in my project 
contains the code I have tested yacc with. It is copied from the bottom of page 986.
To run lex on test, enter the command:
./yacc test