Lab 7: Pascal's Triangle

Objectives

During this lab session:

Students will write a simple Ruby on Rails application.

This activity helps students develop the following skills, values and attitudes: ability to analyze and synthesize, capacity for identifying and solving problems, and efficient use of computer systems.

Activity Description

This lab can be developed individually or in pairs.

Create a Ruby on Rails application called pascal. Inside this application, generate a controller called triangle with two actions: input and draw.

The Ruby source file triangle_controller.rb must start with a comment containing the lab's title, date, and the authors' personal information. For example:
```
# Lab 7: Pascal's Triangle
# Date: 29-Oct-2009
# Authors:
# 456654  Anthony Stark 
# 1160611 Thursday Rubinstein
```

Create a layout file for the application with the following content:

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

  <head>

    <style type="text/css">

      body {
        background: #FFFFFF;
        color: #000080;
        font-family: sans-serif;
        font-size: medium;
        margin: 20px;
      }
      
      hr {
        border: 0;
        color: #B0C4DE;
        background-color: #B0C4DE;
        height: 1px;
      }

      table {
        border-collapse: collapse;
        border: 1px solid #000000;
        padding: 0px;
        margin-bottom: 10px;
        color: #000000; 
        background: #E6E6FA;
      }

      td {
        border: 1px solid #000000;
        padding: 10px;
        text-align: center;
      }

      th {
        border: 1px solid #000000;
        padding: 10px;
        color: #008080;
        background: #B0E0E6;
      }
      
      .footer {
        font-size: 70%;
        color: #B0C4DE;
        text-align: center;
      }

    </style>

    <title><%= yield :title %></title>

  </head>

  <body>    
    <%= yield :layout %>    
    <hr/>    
    <p class="footer">
      Software Design and Architecture              
    </p>
  </body>

</html>

Modify the input.html.erb file so that it contains a web form with a text field that asks for a number n between 0 and 99. It should look like this:

When the submit button labeled "Send" is pressed, the action draw should be requested.
The draw action and view must work together in order to display the diagonals 0 to n of Pascal's triangle (using the <table>, <tr> and <td> tags).

This is how the triangle should be built: the first row and column are composed of ones; all other elements are computed by adding the element immediately above plus the element immediately to the left. In the resulting table, all cells that are not part of the triangle should be left blank. For example, for n = 5, the output should look something like this:

Deliverables

To hand in your lab work, follow these instructions:

Create a ZIP file with the full contents of the pascal directory. Call this file pascal.zip.
Using the Online Assignment Delivery System (SETA), deliver the ZIP file. Due date is Friday, October 30.

Evaluation

This activity will be evaluated using the following criteria:

100	The code works as requested.
60-90	The code works, but has some flaws.
20-50	The code doesn't work, but it seams that some amount of time was spent on it.
DA	The program was plagiarized.