diff --git a/parser/parser.lex b/parser/parser.lex
index 685e8a0..42b48b2 100644
--- a/parser/parser.lex
+++ b/parser/parser.lex
@@ -12,6 +12,7 @@
 
     /* operators */
 :=      return ASSIGN;
+::=     return DASSIGN;
 ==      return DEQUALS;
 \/      return DIVIDE;
 =       return EQUALS;
@@ -41,16 +42,16 @@
 \)      return RPAREN;
 
     /* literals */
--?[0-9]+ {
+[0-9]+ {
         return INT_LITERAL;
 }
--?0x[0-9]+ {
+0x[0-9A-Fa-f]+ {
         return INT_LITERAL;
 }
--?0b[01]+ {
+0b[01]+ {
         return INT_LITERAL;
 }
--?[0-9]*\.[0-9]+([eE][0-9]+)? {
+[0-9]*\.[0-9]+([eE]-?[0-9]+)? {
         return REAL_LITERAL;
 }
 
@@ -59,6 +60,8 @@ byte        return BYTE;
 ubyte       return UBYTE;
 char        return CHAR;
 wchar       return WCHAR;
+short       return SHORT;
+ushort      return USHORT;
 int         return INT;
 uint        return UINT;
 long        return LONG;
diff --git a/parser/parser.yy b/parser/parser.yy
index 55ec6d7..6d73a5b 100644
--- a/parser/parser.yy
+++ b/parser/parser.yy
@@ -27,6 +27,7 @@ int yywrap()
 
     /* operators */
 %token ASSIGN;
+%token DASSIGN;
 %token DEQUALS;
 %token DIVIDE;
 %token EQUALS;
@@ -64,6 +65,8 @@ int yywrap()
 %token UBYTE;
 %token CHAR;
 %token WCHAR;
+%token SHORT;
+%token USHORT;
 %token INT;
 %token UINT;
 %token LONG;
@@ -114,7 +117,7 @@ import_name_more_more: IDENTIFIER import_name_more
                      | STAR
                      ;
 
-function: type IDENTIFIER LPAREN parameter_list RPAREN LCURLY function_items RCURLY
+function: IDENTIFIER LPAREN parameter_list RPAREN COLON type LCURLY function_items RCURLY
         ;
 
 function_items: /* empty */
@@ -133,6 +136,8 @@ primitive_type: BYTE
               | UBYTE
               | CHAR
               | WCHAR
+              | SHORT
+              | USHORT
               | INT
               | UINT
               | LONG
@@ -152,7 +157,7 @@ struct_item: variable_declaration
 variable_declaration: variable_spec SEMICOLON;
                     ;
 
-variable_spec: type IDENTIFIER
+variable_spec: IDENTIFIER COLON type
              ;
 
 ptr_type: type STAR
@@ -179,6 +184,7 @@ expression: assign_expr
           ;
 
 assign_expr: lvalue ASSIGN expression
+           | lvalue DASSIGN expression
            ;
 
 lvalue: IDENTIFIER