CS U216 -- Algorithms and Data Structures for Engineers

Assignment 2

Due 18 May, 2005

Assignment 2 is similar to Assignment 1, but the functionality of the program now includes validation of inputs, and repetative interaction with the user, for as long as the user desires. Additionally, there is a non-functional requirement for this assignment. The program must be written to take advantage of functional abstraction. These requirements will be clarified in the Requirements section.

Write a C++ program that prompts for and reads a patient's name, weight in pounds, and height in feet and inches, and then calculates and displays the patient's name, mass in kilograms, height in meters, and Body Mass Index (BMI), and then repeats this process any number of times. For example:

What is the patient's name? Arnolda
What is the patient's weight in pounds? 100
What is the patient's height in feet and inches? 5 1

Arnolda's weight is about 45.36 kilograms.
Arnolda's height is about 1.5494 meters.
Arnolda's BMI is approximately 18.895 .

Would you like to calculate the BMI for another patient (y/n)? y

What is the patient's name? Jason
What is the patient's weight in pounds? 0.0
I'm sorry, that is not a valid value for this item. Please try again. What is the patient's weight in pounds? 120
What is the patient's height in feet and inches? 5 13
I'm sorry, that is not a valid value for this item. Please try again. What is the patient's height in feet and inches? -3 7
I'm sorry, that is not a valid value for this item. Please try again. What is the patient's height in feet and inches? 5 7

Jason's weight is about 54.432 kilograms.
Jason's height is about 1.7018 meters.
Jason's BMI is approximately 18.7948 .

Would you like to calculate the BMI for another patient (y/n)? z
I'm sorry, that is not a valid value for this item.
Would you like to calculate the BMI for another patient (y/n)? n

In the example above, the italic or slanted text represents input typed by a user of the program. The rest of the text represents the prompts and other output of the program.

Requirements

Functional Requirements

• The program must run the example above almost exactly as shown. The only variations allowed are in the calculated numbers, which may vary slightly from one computer system to another.
• The program must run similar examples similarly, with the only changes coming in the name of the patient and in the numbers that are provided by the user or calculated by the program.
• If the user responds with a y for the last question, the interaction between the program and user will be repeated. If the user responds with a n for the last question, the interaction will terminate, and the console window will close. If the user responds with any other value, the question will be repeated.
• The following cases correspond to invalid inputs. When an invalid input is entered by the user, a warning will be output, and the program will re-prompt the user for the input. This may be repeated any number of times.
  • The weight entered is less than 0.1
  • The inches portion of the height entered is less than 0.0 or greater than or equal to 12.0
  • The height entered is negative.

Non-functional Requirements

• The program must be divided into functions. In particular, for each value requested, there must be a function that returns that value as the result of user input. These functions may call (and in fact will call) other functions, but must not terminate until a valid value has been input (or a run-time error has occured.)
• The program must contain a function that prints out the warning message for invalid inputs. This function must be called by each function that prompts for, and returns a validated input. (Note, the program does not validate the patient's name.)

Background Information

A person's Body Mass Index (BMI) is defined to be the person's mass m in kilograms divided by the square of the person's height h in meters. In C++ this calculation would be written as m / (h * h).

There are still a few corners of the world where the old English system of measures remains in use. In the United States, the Omnibus Trade and Competitiveness Act of 1988 declared the International System of Units (SI) to be the preferred system for trade and commerce, but many citizens continue to think in terms of pounds and inches. This program accomodates them.

One pound corresponds to approximately 453.6 grams, which is .4536 kilograms. One inch corresponds to 2.54 centimeters, which is .0254 meters. One foot equals twelve inches. Hence:

• To convert pounds to kilograms, multiply by .4536.
• To convert feet to inches, multiply by 12.
• To convert inches to meters, multiply by .0254.

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Last updated 11 May 2005.