grammar.txt

Tools
____________________________________________

Scanner Tool 		FLex
Parser Tool		Generator	YACC/Bison
____________________________________________

Symbol Table Implementation
____________________________________________

Using a hash table implementation, with
chaining to handle collisions.
Chaining done using linked lists.
Each entry into the hash table has token name,
token type, token value ,current scope binding
Scoping is done by following a name convention
where, a block with scope_id A, has sub_blocks
with scope_id A1.

____________________________________________


Grammar :
				Language : C++
Reference
---------------------------------------------
Symbol			Description
---------------------------------------------
p			Program
ret_type 		Return type
s			Statement (general)
dec_stat		Declaration statement
assign_exprn	Assignment expression
unary_exprn	Unary expression
cond			Condition
exprn			Expression
num			Number(value) (terminal)
sel_stmt		Selection statement
id			ID of the variable (terminal)
class_id		ID of the class name (terminal)
func_id		ID of the function name (terminal)
log_exprn		Logical expression
rel_exprn		Relational expression
logop			Logical operator
relop			Relational operator
uop			Unary operator
bitop			Bit operations
LT			Less than (terminal)
GT			Greater than (terminal)
LTEQ			Less than or equal (terminal)
GTEQ			Greater than or equal (terminal)
NEQEQ			Not equal to (terminal)
EQ			Equal to  (terminal)
---------------------------------------------

P 
		: program
  		;

program	
		: external_declaration
		| program external_declaration
		;

external_declaration 
		: header_stmt
		| global_stmt
		| main_fun
		;
					 
header_stmt 
		: '#' T_INCLUDE '<' T_IDH '>'
		| '#' T_INCLUDE  T_IDH
		;

global_stmt 
		: declaration_statement 
		| fun_declr
		| user_defined_ds
		| statement
		;
			
main_fun 
		: T_TYPE T_MAIN '(' ')' compound_stmt
	    ;
		   
			
declaration_statement 
		: T_TYPE list_identifier ';'
		;
		
list_identifier 
		: list_identifier ',' variable 
		| list_identifier ',' init
		| init 
		| variable
		;
				
variable 
		: T_IDENTIFIER 
		| T_IDENTIFIER array
		 ;
		 
array 
		: array '[' T_INTEGER_VAL ']'
	  	| '[' T_INTEGER_VAL ']'
	  	;
	  
init 
		: var_init
     	| array_init
	 	;
	 
var_init 
		: T_IDENTIFIER '=' expression
		 ;
		 
array_init 
		: T_IDENTIFIER array '=' '{' values '}'
		;
		   
values 
		: values ',' constant
   	    | constant
		;
	   
constant 
		: T_INTEGER_VAL
		| T_STRING_VAL
		| T_CHAR_VAL
		| T_FLOAT_VAL
		;
		 
declarator 
		: '(' ')'
		| '(' params ')'
		;

fun_declr 
		: T_TYPE T_IDENTIFIER declarator compound_stmt
		;
		 
params_list 
		: T_TYPE T_IDENTIFIER 
		| params_list ',' T_TYPE T_IDENTIFIER
		;
		 
params 
		: params_list
       	;
		 
compound_stmt 
		: start_paren end_paren
		| start_paren block_item_list end_paren 
		;
			  
start_paren 
		: '{'
		;

end_paren 
		: '}' 
		;	  
block_item_list 
		: block_item
		| block_item_list block_item
		;

block_item 
		: declaration_statement
		| statement
		;   
		   
user_defined_ds 
		: class
		| structure
		;
				
class 
		: T_CLASS T_IDENTIFIER class_body_stmt ';'
		;

structure 
		: T_STRUCT T_IDENTIFIER struct_body_stmt ';'
		;

class_body_stmt  
		: start_paren end_paren
		| start_paren class_mems end_paren 
		;
				 
struct_body_stmt  
		: start_paren end_paren
		| start_paren struct_mems end_paren 
		;

struct_mems 
		: struct_mem
		| struct_mems struct_mem
		;

class_mems 
		: class_mem
		| class_mems class_mem
		;

struct_mem 
		: declaration_statement
		| fun_declr
		;

class_mem	
		:  T_TYPE class_var_declaration ';'
		|  fun_declr
		|  access_specifier ':'
		;
			
class_var_declaration 
		: T_IDENTIFIER
		| class_var_declaration ',' T_IDENTIFIER 
		;

access_specifier 
		: T_PRIVATE
        | T_PUBLIC
		| T_PROTECTED
		;
		     
statement 
		: expression_stmt
		| compound_stmt
  		| iterative_statement
  		| selection_statement
		| input_output_statements
        | return_stmt
  		;
		  
expression_stmt
    	: ';' 
    	| expression ';'
    	;
selection_statement 
		: T_IF '(' expression ')' statement
        | T_IF '(' expression ')' statement T_ELSE else_stmt statement
        ;
					
iterative_statement 
		: for_loop
		| while_loop
  		;

for_loop 
		: T_FOR '(' for_assgn_stmt ';' {} expression ';' unary_exprn ')' statement
  	   	;

for_assgn_stmt 
		: T_TYPE for_decl_stmt
		| assignment_expression
		;

for_decl_stmt 
		: T_IDENTIFIER '=' expression 
		| for_decl_stmt ',' T_IDENTIFIER '=' expression
		;

while_loop 
		: T_WHILE '(' expression ')' statement
  		;
		   
return_stmt 
		: T_RETURN ';' 
		| T_RETURN expression ';'
		;
			
expression 
		: assignment_expression
		| simple_expression
		;
		   
assignment_expression 
		: T_IDENTIFIER '=' expression 							  
		| unary_exprn
		;
					  
unary_exprn 
		: T_ADDADD T_IDENTIFIER
		| T_MINMIN T_IDENTIFIER
       	| postfix_expression
      	| T_IDENTIFIER uop_shorthd expression
		;
			
postfix_expression 
		: T_IDENTIFIER T_ADDADD
		| T_IDENTIFIER T_MINMIN
		;

uop_shorthd  
		: T_ADDEQ
        | T_MINEQ
        | T_MULEQ
        | T_DIVEQ
		;
			 
simple_expression 
		: additive_expression 
		| additive_expression relop additive_expression
		| additive_expression logop additive_expression
		| additive_expression bitop additive_expression
		;
				  
bitop 
		: T_OR
   	  	| T_AND
	  	| T_XOR
	  	| T_LRSHIFT
	  	| T_LLSHIFT
	  	;
				  
relop 
		: '<'
      	| '>'
	  	| T_LTEQ
	  	| T_GTEQ
	  	| T_NEQEQ
	  	| T_EQEQ
	  	;

logop 
		: T_OROR
	  	| T_ANDAND
	  	;
	  
additive_expression 
		: term 
		| additive_expression '+' term 
		| additive_expression '-' term
		| '+' additive_expression %prec '*'
		| '-' additive_expression %prec '*'
		;

term 
		: factor
	 	| term '*' factor	
     	| term '/' factor
  	 	;

factor 
		: '(' expression ')'
	   	| T_IDENTIFIER
	   	| call
	   	| T_INTEGER_VAL
	   	| T_FLOAT_VAL
	   	| T_STRING_VAL
	   	| T_CHAR_VAL
	   	;

call 
		: T_IDENTIFIER '(' ')'
	 	| T_IDENTIFIER '(' args ')'
	 	;

args 	: expression
	 	| expression ',' args
	 	;

input_output_statements 
		: T_COUT T_LLSHIFT expression ';'
		| T_CIN T_LRSHIFT T_IDENTIFIER ';'
		;