Formatting Output

• Sometimes we need to be able to change the way the stream handles numbers.
• This is done through another library
  • #include <iomanip>
• This provides a number of stream manipulators.
  • all are used in the form
    • cout << manipulator
  • Some take parameters some do not.
  • Most are long term, but some are one shot.
  • Caution, some of these behave differently when others are in place.
• setw
  • Takes a single integer parameter, n.
  • The next thing output will take at least n character spaces.
  • It will pad with space if necessary.
  • One Shot.
  • cout << setw(10) << "hello"
  • _____hello (assume _ is a space)
  • But the next output will be spaced normally.
  • If n is too small, the normal output will occur.
  • cout << setw(2) << "hello"
  • hello
• showpoint
  • All floating point numbers are printed with a decimal point
  • Normally 3.00000 will be printed as 3
• fixed and scientific
  • Show as fixed numbers a.bcd
  • Or as scientific numbers a.bEc
  • Default switches on what the programmers though was best.
  • defaultfloat restores the result.
• setprecision(n)
  • Sets the decimal precision to be n.
  • Rounding of the output (but not the variable) will occur.
• Write a program that will read in an integer n and print out the following table (assume the input is 3)

  123456789012345678901234567890  // this line is not part of the output.
           n                   3
         1/n             0.33333  // accurate to five decimal places
         n+n                   6
         n^2                   9
         n^3                  27
          n!                   6
     sqrt(n)               1.732  // accurate to three decimal places