Integer Operations

• The operations are discussed in general here
• A unary operation only involves one number.
  • -3
• A binary operation involves two numbers
  • 3+2
• +,- and *
  • Are addition, subtraction and multiplication.
  • These are closed under the integers.
  • Ie you add two integers, you get an integer back.
  • And are, within overflow, closed on the integer types.
• / and %
  • These are division and remainder.
  • For the integers these are not closed.
    • 7/2 = 3.5 or 3 R 1 in mathematics.
    • In c++ 7/2 is integer division and is 3.
    • Integer division rounds down.
    • In c++ 7%2 is integer remainder and is 1.
    • % is sometimes called modulus.
• Operator precedence: please excuse my dear aunt sally
  • Do parenthesis first ()
  • Do exponentiation next, but we put this off for a bit.
  • Do multiply, divide and modulus from left to right.
  • Do add and subtract from left to right.
  • See The operator precedence table at cppreference.
• C had several convenience functions
  • Compound assignment
    • we do this all of the time :
    • var = var op expression
    • Ie a = a * 5
    • As a shortcut, c and c++ have the functions
    • var op= expression
    • IE a *= 5
    • This works for +, -, *, /, % and others.
  • prefix/postfix increment and decrement
    • We also do this all of the time:
    • i = i + 1
    • So c provided the shortcuts
      • ++i
      • i++
      • and --i and i--
    • There is a difference if they are used in an expression.
    • The prefix operators (++i) return the old value of I then increment
    • The prefix operators (i++) increment and return the new value of i.
  • Take a look at intOps.cpp.
• There are more operators.
  • & is bitwise and
  • | is bitwise or
  • ~ is bitwise not.
  • << is shift left
  • >> is shift right.
• See intBit.cpp.