teaching machines

CS 145 Lecture 11 – Conditionals

October 17, 2011 by Chris Johnson. Filed under cs145, fall 2011, lectures.

Agenda

• how’d the exam go?
• what does this do?
• conditionals in Secret Maryo Chronicles
• pluralizing
• generating a star
• generating an ordinal number
• categorizing light — if/else if

What does this do?

1. public static boolean snarfFlob() {
     return !isAlarmOn && (isHoliday || isWeekend);
   }

2. public static int getFlooper(int n) {
     if (n % 2 == 1) {
       return n - 1;
     } else {
       return n;
     }
   }

3. public static int bupperBap(Scanner in) {
     while (!in.hasNextInt()) {
       in.next();
     }
     return in.nextInt();
   }

Code

Conditional.java

package lecture;

public class Conditional {
  
  public static void main(String[] args) {
    star(100);
    System.out.println(pluralize("Nick", 42));
    System.out.println(pluralize("Nick", 1));
    System.out.println(pluralize("Nick", -1));
    System.out.println(pluralize("Nick", -87));
  }
  
  /*
   * dog, 1 -> 1 dog
   * dog, 5 -> 5 dogs
   * child, 3 -> 3 childs
   * moose, 4 -> 4 mooses
   * code, 1 -> 1 code
   */
  public static String pluralize(String object, int n) {
//    String nonplural = n + " " + object;
//    if (n == 1 || n == -1) {
//      return nonplural;
//    } else {
//      return nonplural + "s";
//    }
    
    String answer = n + " " + object;
    if (Math.abs(n) != 1) {
      answer = answer + "s";
    }
    return answer;
  }
  
  public static void star(int nPoints) {
    
    // walk around circumference of circle
    // print each point (x, y)
    
    double angle = 0.0;
    double delta = 2.0 * Math.PI / nPoints;
    
    for (int i = 0; i <= nPoints; ++i, angle += delta) {
      // print out (x,y)-coordinate for this angle
      if (i % 2 == 1) { // if odd
        System.out.println(Math.cos(angle) * 0.5 + "," + Math.sin(angle) * 0.5);
      } else { // if even
        System.out.println(Math.cos(angle) + "," + Math.sin(angle));
      }
    }
  }
}

TODO

1. Read sections 4.2 – 4.4.