teaching machines

CS 145 Lecture 23 – Loops V

October 24, 2014 by Chris Johnson. Filed under cs145, fall 2014, lectures.

Agenda

• what ?s
• what does this do?
• blackboxes
• loops in other languages

TODO

• Share a quiz question before the quiz in Monday’s lab. Pretend that your question might actually appear in the quiz: make it short, direct, and on topic. Worth a 1/4 sheet.

What Does This Do?

1. public static String ?(String raw) {
     String cooked = "";
     for (int i = 0; i < raw.length(); ++i) {
       if (Character.isLetterOrDigit(raw.charAt(i))) {
         cooked += raw.charAt(i);
       } else {
         cooked += "_";
       }
     }
     return cooked;
   }

   show

2. public static boolean ?(int n) {
     for (int i = 2; i < n; ++i) {
       if (n % i == 0) {
         return false;
       }
     }
     return true;
   }

   show

3. public static void ?() {
     for (int r = 1; r <= 5; ++r) {
       for (int c = r; c >= 0; --c) {
         System.out.print(c);
       }
       System.out.println();
     }
   }

   show

Blackboxes

• Blackbox 7
• Blackbox 6
• Blackbox 8

Code

ForFor.java

package lecture1024;

public class ForFor {
  public static void main(String[] args) {
    mystery();
  }
  
  public static void mystery() {
    for (int r = 1; r <= 5; ++r) {
      for (int c = r; c >= 0; --c) {
        System.out.print(c);
      }
      System.out.println();
    }
  }
}

Haiku