ITEC 120 2008spring ibarland, jdymacek

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lab04b-soln
if-else-if, continued

We will spend most of today finishing up the ebay lab from Tuesday (including the three-tiered price structure for items over $1000.)

Practicing with quotient, remainder

First though, we'll take ten minutes to look at / for doubles vs. / for ints vs. % (remainder).

Remember that /, if given two integers, returns the quotient. The remainder can be obtained by % (pronounced “mod” or “modulo” in addition to “remainder”). Predict the result of each expression to your partner, then try them out:

• 260.0 / 100.0
• 260 / 100
• 260 % 100
• Suppose somebody walks up into a change-machine and dumps in a bucket of small change — n¢ worth. You'll first calculate how many quarters to return, and then calculate how much money you still owe the person, and then calculate how many additional dimes to give them.

  int n = 1234; // Or however much money was dumped in, in cents. n // Type this in code pad, just to check its value. int quartersBack; // How many quarters we'll return. quartersBack =   n / 25  ; int stillDue25; // How much money we still owe back, after quarters. stillDue25 =   n % 25  ; quartersBack // Type this in code pad, just to check its value. stillDue25 // Type this in code pad, just to check its value. int dimesBack; dimesBack =   stillDue25 / 10   stillDue10 =   stillDue25 % 10   int nickelsBack; nickelsBack =   stillDue10 / 5   stillDue5 =   stillDue10 % 5

  (solution)
  Two notes:
  • Instead of expressing stillDue25 as n%25, you could have written n - quartersBack*25, which is the same as n - (n/25)*25. In fact, this is a general fact: for any ints p,q where q != 0, p%q = p - (p/q)*q.
  • Could you write the above without any local variables — only using n? Yes!
    The amount of dimes back is   ((n%25) / 10)  , and the amount of nickels back will be   (((n%25) % 10) / 5  .
  (solution)

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©2008, Ian Barland, Radford University Last modified 2008.Feb.06 (Wed)

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