compiler_project_structures

The Main Structures Comprising the Compiler Project Code
Spring 08

Prog (the representation of the user input program)
Root (symbol table)
Semantic Stack (compiler writer's tool to keep track of meaningful quantities encountered during the parse)

The scanner generated by lex separates the user input program into tokens based on our definition of the language tokens in simple.lex

The parser generated by yacc performs the syntax-directed translation obeying our statement of the language grammer in simple.lr

The Compiler Structures outlined below are:

Prog [Global var with statement list, variable list and constant lists]
Root [Global pointer to our Symbol Table [Binary Search Tree])
SymbolTable [Symbol Table Entries - Attribute Record and Left and Right child]
Attrec [Attribute Record for each variable name specifying its properties]
Variable List [Alpha-order variable names created as last step of front-end of translation]
Statement Node [Semantic Info for each type of statement, will be placed in AST]
ExprDesc Expression Description to build AST
AddrNode [Adress information for variable name]
ParamNode [description of I/O parameter - Read (address) - Write (ExprTree)]
SemStack [Semantic Stack Entries]

(astdef.h)

**PROG**
programtree
Prog.main	Stmtlist	list of statements
Prog.vars	Varlist	alpha-list of variable names
Prog.const_listptr		list of string constants
	info	^ character string
	offset	integer field to hold label index
	next	^ next in list of global strings

**STMTNODE**
**statement description**
type:	STMTTYPE	AssignStmt StdProcCall IfThenStmt
	ifthen	se.bexpr	boolean ExprTree
		se.slist	list of statements comprising the "then-block"
	assign	se.lhs	^Address Tree
		se.rhs	^Expression Tree
	procoll	se.type	ReadProc ReadlnProc WriteProc WriteLnProc
		se.params	List of Parameters

**EXPRDESC**
**Expression Tree Node Description**
height:		height of exprTree
OP:		+ - * / - fetch
ee.	ee.addr	^Address Tree [fetch]
	ee.child	^Expression Tree [Usubop]
	ee.left	^Expression Tree (AddOp SubOp MpyOp DivOp)
	ee.right	^Expression Tree (AddOp SubOp MpyOp DivOp)
	ee.btree	^ Boolean Expression Tree

**PARAMNODE**
**description of actual (I/O) parameter**
Type:	PARAMDESC (Reference Value String)
pe.loc	^Address Tree
pe.val	^Expression Tree
pe.where	^location of string in constlist
pe.next	^next entry in list of parameters of I/O statement

(semstack.h)

**Semstack**
type	SEMSTACKTAG	type of entry
se.addr		^address entry
se.expr		^expression entry
se.id		identifier entry
se.oper		OPERATION entry "typedef enum AddOp,SubOp,MpyOp,DivOp,UsubOp,Fetch,EqOp" in semform.h
se.stmt		statement entry
se.slist	first	statement list entry
	last
se.plist	first	parameter list (I/O) entry
	last