The if Statement

1. The statement writeln("Washing the plate") is written indented as if to be within the else scope. However, because the scope of that else is not written with curly brackets, only the writeln("Eating pie") statement is actually inside the scope of that else.

   Since whitespaces are not important in D programs, the plate statement is actually an independent statement within main() and is executed unconditionally. It confuses the reader as well because of having been indented more than usual. If the plate statement must really be within the else scope, there must be curly brackets around that scope:

   import std.stdio;
   
   void main() {
       bool existsLemonade = true;
   
       if (existsLemonade) {
           writeln("Drinking lemonade");
           writeln("Washing the cup");
   
       } else {
           writeln("Eating pie");
           writeln("Washing the plate");
       }
   }
   

2. We can come up with more than one design for the conditions of this game. I will show two examples. In the first one, we apply the information directly from the exercise:

   import std.stdio;
   
   void main() {
       write("What is the value of the die? ");
       int die;
       readf(" %s", &die);
   
       if (die == 1) {
           writeln("You won");
   
       } else if (die == 2) {
           writeln("You won");
   
       } else if (die == 3) {
           writeln("You won");
   
       } else if (die == 4) {
           writeln("I won");
   
       } else if (die == 5) {
           writeln("I won");
   
       } else if (die == 6) {
           writeln("I won");
   
       } else {
           writeln("ERROR: ", die, " is invalid");
       }
   }
   

   Unfortunately, that program has many repetitions. We can achieve the same result by other designs. Here is one:

   import std.stdio;
   
   void main() {
       write("What is the value of the die? ");
       int die;
       readf(" %s", &die);
   
       if ((die == 1) || (die == 2) || (die == 3)) {
           writeln("You won");
   
       } else if ((die == 4) || (die == 5) || (die == 6)) {
           writeln("I won");
   
       } else {
           writeln("ERROR: ", die, " is invalid");
       }
   }
   

3. The previous designs cannot be used in this case. It is not practical to type 1000 different values in a program and expect them all be correct or readable. For that reason, it is better to determine whether the value of the die is within a range:

       if ((die >= 1) && (die <= 500))