CSCI 1301 - Lab 13

Clément Aubert

March 22, 2018

Deadlines: Part I and Part II are required to be able to turn in Project #3, presented in Part III.

Part I – Truth Tables

Copy-and-paste the following code in the Main method of a new project:

/* 
 * We have two boolean values: true and false.
 * We can use the constant "true" and "false",
 * we can also declare constants with the same value,
 * but a shorter name:
 */
const bool t = true;
const bool f = false;

Console.WriteLine("Conjonction (and, &&) truth table:"
+ "\n\n\t" + t+ "\t" + f
+ "\n" + t+ "\t" + (t && t)+ "\t" + (t && f)
+ "\n" + f+ "\t" + (f && t)+ "\t" + (f && f)
+ "\n\n*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*\n");

Console.WriteLine("Negation (not, !) truth table:"
+ "\n\n\t" + t+ "\t" + f
+ "\n\t" + (!t)+ "\t" + (!f)
+ "\n\n*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*\n");

Compile and execute it.

Then, write the code that will display on the screen the truth tables for the binary operators disjunction (or, ||), identity (equality, ==) and difference (inequality, !=).

Normally, using the find-and-replace feature of VS should make this task easy and fast.

Part II – Precedence and Order of Evaluation

Reading and Understanding

If you look at https://docs.microsoft.com/en-us/cpp/c-language/precedence-and-order-of-evaluation, you will see that

! is evaluated before
*, /, and % which are evaluated before
+ and - which are evaluated before
<, >, <=, and >= which are evaluated before
== and != which are evaluated before
&& which is evaluated before
|| which comes last

and that within those groups, operations are evaluated from left to right.

So that, for instance, ! true || false && 3 * 2 == 5 will be evaluated as

! true || false && 3 * 2 == 6 ⇒ false || false && 3 * 2 == 6
false || false && 3 * 2 == 6 ⇒ false || false && 6 == 6
false || false && 6 == 6 ⇒ false || false && true
false || false && true ⇒ false || false
false || false ⇒ false

Note that an expression like !3 > 2 doesn’t make any sense: C# would try to take the negation of 3, but you can’t negate an integer! Along the same way, an expression like false * true doesn’t make any sense: you can’t multiply booleans! Similarly, 3 % false will cause an error: can you decide why?

Computing Simple Boolean Expressions

Evaluate the following expressions (where t stands for true, and f for false):

Computing Expressions Involving Booleans and Numerical Values

For each of the following expression, decide if they are “legal” or not. If they are, give the result of their evaluation.

Part III – A Guessing Game

Write a program that

  1. Store your favorite number in a variable
  2. Ask the user to enter a numerical value, and store the user’s answer in a variable.
  3. With an if statement, display on the screen “You guessed correctly” if number entered by the user is your favorite number.
  4. Once this part of the program works, add an if statement that displays on the screen “Try a lower value!” if the number entered by the user is strictly greater than your favorite number.
  5. Once this part of the program works, add an if statement that displays on the screen “Try a greater value!” if the number entered by the user is strictly lower than your favorite number.
  6. Once this part of the program works, add an if statement that displays on the screen “You found a multiple of my favorite number!” if the number entered by the user is a multiple of your favorite number, but different from it.

Part IV – Pushing Further (Optional)

This lab’s “Pushing Further” combines Part 1 and our previous study of static class members. The goal is to design a static class that will be used to return truth tables as string.

  1. Start by reading about static classes at https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/static-classes-and-static-class-members
  2. Ask yourself: why would we want the class that contains methods to return truth tables to be static?
  3. Start writing the class: start with static class TruthTable, add two private constants for the two boolean values. No need to declare them static: a const attribute of a class is always static!
  4. Write the first method: a static method that returns a string, the truth table for the conjonction, takes no argument, and is called And.
  5. Make sure your class is working: in the Main method, call your method, using TruthTable.And(), and display on the screen the string it returned.
  6. Write the methods that returns the other truth tables.
  7. Write a static method that takes a string argument, and returns the truth table for the conjonction if the argument is “and” or “&&”, the disjunction if the argument is “or” or “||”, etc. You can use if, if-else, or switch, to do so. Have a look at the documentation (for instance, https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/if-else for if-else, https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/switch for switch).