Solution of the simple task: Begin3
This section contains description of solving the following simple task in Ruby:
Begin3°. The sides a and b of a rectangle are given.
Find the area S = ab and the perimeter P = 2(a +
b) of the rectangle.
We shall use the NetBeans IDE 7 as programming environment, however the same results may be
received in the NetBeans IDE 6.
Creating a template and acquaintance with the task
The created template is located in the PT_Ruby subdirectory of the working directory and
consists of several files and subdirectories. But we need only MyTask.rb file.
This file will be loaded into the code editor of NetBeans IDE:
# File: "Begin3"
After loading the template project into the NetBeans IDE the project information will
be output in the left-hand side of the IDE windows.
The MyTask.rb file contains definition of the solve function that
already contains the task function
call that initializes the Begin3 task.
The solution of the task should be entered in the solve function
(of course any other functions may be used).
To run the program press [F6] key. When the program is launched
you will see the Programming Task window with a task text and
This running is considered as acquaintance running because
the program does not perform input-output operations.
To close the Programming Taskbook window click the "Exit" button or press [Esc] or [F6] key.
Initial data input
Before solving tasks you should input initial data in the program.
In the Begin3 task the initial data are real numbers a and b
that refer to sides of the rectangle.
There are two functions that provide input of the real numbers: the get
function and the get_f function. The get_f function also
checks type of the current data item and
output error message if the type of data item differs from the Float type.
Let's use the get_f function (we omit the
require statement in this listing):
a = get_f
b = get_f
Run the program once again. You will see the new set of initial data. For each running of the
program a new initial data are generated, so it is necessary to develop an algorithm that processes correctly
all admissible sets of initial data.
Data input is performed correctly, but the program does not output results.
In such situation we have
the following message: "Correct data input: all required data are input, no data are output"
(Programming Taskbook version 4.15 or higher) or "Some data are not output" (previous versions).
Calculation and output results
Let's perform the required calculations and output results using the put
a = get_f
b = get_f
p = 2 * (a + b);
s = a * b;
put P, S
In this case the running leads to the following information in the status bar:
"Error NameError: uninitialized constant P".
To correct the program it is enough to change its last statement as follows:
put p, s
When the program is running you can see output values at the panel of results.
Because we output data in inverse order, the status bar contains the error message "Wrong solution".
Right solution and its testing
To correct the last error it is enough to change order of two parameters of the put function:
put s, p
When this program is running you will see the testing panel on screen:
This panel appears when the program processes successfully at least one set of input data.
The progress bar shows the amount of tests which are already performed,
the text above the bar allows to determine how much tests should be performed successfully.
The program testing finishes in two cases: when all required tests are performed successfully
or when some test is failed.
In our case the algorithm is correct, therefore the message
"The task is solved!" will be shown.
To browse information about the task solving you can use PT4Results tool
(you may run this tool by pressing the [F2] key or clicking the "Results" label in the upper-right corner of
the Programming Taskbook window):
Begin3 r23/02 20:13 Acquaintance with the task.
Begin3 r04/02 15:07 Correct data input.
Begin3 r04/02 15:09 Error NameError.
Begin3 r04/02 15:12 Wrong solution.
Begin3 r04/02 15:15 The task is solved!
The letter "r" denotes the programming language being used (Ruby).
a, b = get, get
put a * b, 2 * (a + b)
Also we can use the put methods without parameters as followa:
a, b = get, get
(a * b).put
(2 * (a + b)).put