Overview of C++ Operators

Operators
• Unary operators are those that take a single operand, e.g., !(logical not), ++, --
• Binary operators are those that take two operands, e.g., =, ==,||, &&
• Some symbols represent both unary and binary operators, e.g., - can be unary or binary
• Arithmetic operators, e.g., +, -, *, /, %
• Equality, Inequality and Relational operators, e.g., ==, !=, >=, <=, >, <
• Logical Operators, e.g., !, &&
• Bitwise operators, e.g., ~, <<, >>, &, |, ^

Lvalues and Rvalues
• When a variable is defined in a C++ program there are always two values associated with that variable
• The term rvalue is used to refer to the variable's read value or the value that the variable contains
• The term lvalue is used to refer to the variable's location value
• For example:
  

  char c = 'a';	c is a lvalue, 'a' is a rvalue
  c = c + 1;	// c on the left hand side is a lvalue
  		// c on the right hand side is a rvalue
  

• Rvalues cannot be used to change a variable's value. Whenever the value of a variable is accessed, its rvalue is used. Constants can only be rvalues
• Lvalues allow a variable to be changed. To change a variable you need its lvalue. A reference variable is a lvalue of another variable:
  

  char c = 'a';
  char& ref = c;	// assign the lvalue of c to ref
  char c2 = c; 	// assign the rvalue of c to c2
  ref = 'b';	// change the rvalue that ref refers to
  

Assignment Operator
• The left operand must be a lvalue (only a lvalue can have its rvalue changed:
  

  int x = 10;
  intarray[3] = x; 
  

• The return value of an assignment is a reference to the left hand side of the assignment expression:
  

  (ch = cin.get()) != EOF; 	// compare new value of ch with EOF
  

• Assignment operations are evaluated from right to left; they can be concatenated:
  

  x = y = z;
  // Is the same as:
  y = z;
  x = y;
  

• Compound assignment:
  

  x += 7; 	// Is the same as x = x + 7