C++ looping question
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CS 171 Computer Programming 1 Winter 2017
Assignment 3: Loops and Reference Parameters
Purpose:
After completing this assignment you will have designed, implemented, debugged, compiled and provided documentation for a C++ program that involves loops and reference parameters
The Assignment:
This assignment consists of:
1. A custom problems requiring you to write functions that may include branches, functions, loops and reference parameters.
In addition to the problem specifications, this document contains:
• What to Submit • Grading Rubric • Academic Honesty
Make sure you read everything!
Problem 1
A person's Blood Alcohol Concentration (BAC) has been strongly correlated with driving impairment to the extent that there are legal designations regarding level of impairment. See charts such as http://www.brad21.org/bac_charts.html for examples -‐ this page contains links for female and male BAC charts. While actual blood alcohol level varies with the individual and the situation, the mathematical model explained below yields fairly accurate predictors for most people.
There are several factors involved in computing a person's BAC -‐ including amount of alcohol consumed, duration of the drinking session, the person's weight, and their gender. (Other factors, such as age, physical condition, amount of food consumed, etc. are not taken into account. Your mileage may vary.)
For our purposes:
• The amount will be measured in number of drinks, which is equivalent to a 12 oz. beer, 1.25 oz. of 80 proof liquor, or 5 oz. of table wine;
• The duration will be measured in minutes. Our calculations will assume BAC reduces by .01 for each 40 minutes spent drinking. What this means is that if you have five drinks but do this over two hours, your BAC is reduced compared to what would be if you drank five drinks quickly in a row and then immediately measured your BAC;
• The weight will be measured in pounds • The formulas vary according to gender.
So, how do we determine a person's BAC? This is the volume of alcohol in the bloodstream divided by the volume of blood. The volume of alcohol is proportional to the amount ingested and the volume of blood is proportional to the person's weight, so that the BAC can be found by dividing the number of drinks by the person's weight and multiplying by a constant. The constant is 4.5 for females and 3.8 for males. The BAC gets reduced by the time spent after the last drink by .01 for each 40 minutes. For example, for a 130 pound woman who has consumed 3 drinks and then waited 80 minutes to take her blood alcohol concentration would have a BAC of approximately 0.084. A 160 pound woman who consumed 3 drinks then waited 300 minutes to take her blood alcohol concentration would have a BAC of approximately 0.0094.
The BAC model predicts certain effects according to BAC. DUI laws specify a penalty for higher concentrations of BAC. The following table describes notable relationships:
BAC 0.00 0.00–0.04 0.04–0.08 0.08–0.10 ≥0.10
Description Safe to Drive
Some Impairment
Driving Skills Significantly Affected
Criminal Penalties in Most US States
Legally Intoxicated -‐ Criminal Penalties in All US States
For each category, the lower bound is strict; that is a driver with BAC=0.08 is in the "Criminal Penalties in Most US States" category. The only exception is "Some Impairment", which begins at any value above 0.
To the above table we add the additional information that if the concentration is above 0.30, death is possible.
Our ultimate goal is to write a program that allows the user to enter the weight, sex and time since last drink, and then prints out a table of information showing the status according to the BAC
Below is a sample output (with proper formatting):
Enter your weight (in lbs): 150 How many minutes has it been since your last drink? 0 Enter your sex as M or F: F 150 pounds, female, 0 minutes since last drink # drinks BAC Status 0 0.000 Safe To Drive 1 0.030 Some Impairment 2 0.060 Driving Skills Significantly Affected 3 0.090 Criminal Penalties in Most US States 4 0.120 Legally Intoxicated - Criminal Penalties in All US States 5 0.150 Legally Intoxicated - Criminal Penalties in All US States 6 0.180 Legally Intoxicated - Criminal Penalties in All US States 7 0.210 Legally Intoxicated - Criminal Penalties in All US States 8 0.240 Legally Intoxicated - Criminal Penalties in All US States 9 0.270 Legally Intoxicated - Criminal Penalties in All US States 10 0.300 Legally Intoxicated - Criminal Penalties in All US States 11 0.330 Death is Possible!
We help you develop this program by describing a series of functions. You will have additional latitude in design, so will also submit your source code and output on Blackboard to be looked at by the graders.
Using the information given above, design and implement a function that has the following prototype:
void computeBloodAlcoholConcentration(int numDrinks, int weight, int duration, double &maleBAC, double &femaleBAC);
This function computes the blood alcohol concentration for the given number of drinks, the given weight, and the given elapsed time since the last drink (duration). It returns via reference parameters both the male and female blood concentrations for that.
Note: Error tolerance in answers returned by computeBloodAlcoholConcentration
As we (hopefully) recall, floating point arithmetic introduces little errors in calculations because of the limited precision of the numbers. It is not true that basic mathematical facts such as the distributive, associative, or commutative laws hold for computations done with floats or double. At any rate, the errors introduced by using limited-‐ precision arithmetic means that two formulas that are mathematically equivalent may not produce exactly the same results when float or double data and arithmetic is used in the calculation. We aren't forcing you to write the formula you use in the most accurate way (which would be to find an integer-‐based way), so we should be willing to accept any value within a few rounding errors of what we get.
Problem 2
Using the information given, design and implement a function with the prototype:
string impairment(double bac);
that returns (as a string) the appropriate message for the blood alcohol concentration. You should use the global constant declarations as described below.
const double safe = 0.00; const double someImpairment = 0.04; const double significantAffected = 0.08; const double someCriminalPenalties = 0.10; const double deathPossible = 0.30; const string SAFE = "Safe To Drive"; const string SOMEIMPAIR = "Some Impairment"; const string SIGNIFICANT = "Driving Skills Significantly Affected"; const string MOST_STATES = "Criminal Penalties in Most US States"; const string ALL_STATES = "Legally Intoxicated - Criminal Penalties in All US States"; const string YOURE_DEAD = "Death is Possible!";
Problem 3
Once you have these two functions working, write the following three functions whose prototypes are:
• int promptForInteger(const string &message, int lower, int upper); • char promptForMorF(const string &message); • void showImpairmentChart(int weight, int duration, bool isMale);
Descriptions of the functions are as follows:
int promptForInteger(const string &message, int lower, int upper);
When called this function prints out the message and gets an integer. If the integer is greater than or equal to lower and less than or equal to upper then it returns the integer. Otherwise, it loops, asking for an integer again.
(Note: this is a good place to use the do{…}while ( ) ; version of a while loop.)
char promptForMorF(const string &message);
This function prints out the message and returns the value entered as its result. The function checks that the input character entered is an M or an F. If it isn't it just prompts again. You can program the function to check for exactly an upper case 'M' and 'F', or you can do the extra programming to handle things more liberally, as you prefer.
void showImpairmentChart(int weight, int duration, bool isMale);
This function prints a chart similar to that shown in Problem 1 for up to and including ten drinks and with nicely formatted output. We expect a sensible number of decimal digits commensurate with the expected accuracy of the measurements. You may need to stop and think a moment about how much accuracy is warranted. If you recall your high school physics, it's difficult to justify using more digits than the accuracy of the measurements warrant. If we are thinking of a sobriety test administered by the side of the road, it's unlikely that they'd have a scale accurate to the nearest .001 pound for weighing people, nor measure the time since the last drink more closely than to the nearest minute. Your program comments for this function should justify why you used the accuracy you did.
Finally, you must write a main program that uses the code you wrote and prompts the user for:
1. Weight in pounds 2. Time since last drink (in minutes) 3. M or F to indicate that the information is for a male or female.
The program then prints out a single column of the blood alcohol chart in a format similar to that in Problem 1
Submission
All homework for this course must be submitted electronically using Blackboard Learn. Do not e-‐mail your assignment to a TA or Instructor! If you are having difficulty with your Blackboard Learn account, you are responsible for resolving these problems with a TA, an Instructor, or someone from IRT, before the assignment it due. It is suggested you complete your work early so that a TA can help you if you have difficulty with this process.
For this assignment, you must submit:
Problems 1-‐2: NOTHING (kind-‐of)!!
• The work you do will contribute to the last question.
Problem 3:
• Your C++ source code file that contains all the functions of Programs 1-‐3. Just submit your ".cpp" file, NOT your .dsp, .dsw, or similar IDE project files.
• A PDF document with your User Manual • A PDF document with your System Manual • For this assignment we will ask for a test log file in the form of a PDF document
containing screen shots of your program running over several tests. Two or three tests should be suffice. We encourage you to try “odd” tests.
Remember, now that we have functions in our code they all must have proper internal and external documentation
Grading Rubric:
Note that all homework assignments will be given the same weight. The points assigned in a given assignment are simply to provide a natural level of resolution for grading. You can always rescale it to out of 100% if you want.
1. Function from Problem 1 Correct 20pts 2. Function from Problem 2 Correct 20pts 3. Program 3 doesn’t have any syntax errors 10pts 4. Program 3 produces correct result (proper logic) 20pts 5. Program 3 produces correctly formatted output 10pts
In addition, for Program 3 (which includes Program 1-‐3)
4. Coding style: consistent adherence to coding standards described in assignment 2 (the previous assignment). Through use of variable names, indentation, and comments it makes itself easy to comprehend. Those who want to adopt variations need justify their divergences and must provide in your written comments a justification that is persuasive and convincing to the grader. (You may wish to talk to the staff about this rather than assuming that you know what they like.) Coding styles reflect what code readers want to read, not just what programmers want to write.
o 5 points = excellent. Code is included in a .cpp file submitted to blackboard, as well in readable form in the .pdf.
o 4 points = good but a few improvements are in order o 2 points = many improvements needed for code to be readable for a general
audience of programmers, or the formatting of the code in the .pdf or .cpp makes it unpleasant and difficult to read (grader's opinion is what matters here -‐ if you have any doubts, you should ask before submitting.).
o 1 point = missing major principles, should talk to staff about this to do better next time. This is the maximum number of points you can get in this category regardless of style quality if your program does effectively print out the table it was designed to do.
5. Program construction
o 5 points = excellent. Code is not needlessly complex. Functionality is encapsulate d in the mandated functions and used in that fashion in the program submitted. The program is written in a way that makes extension or changes easy to do. Global constants are used as mandated. Computations should not be needlessly complex, use math to simplify calculational expressions or logic to simplify if statements or complicated Boolean expressions. The grader's judgment is the relevant measure here.
o 4 points = good, but a few improvements are in order.
o 2 points = many improvements needed for code to come up to expectation for coding quality.
o 1 point = many flaws, should talk to staff about this. This is the maximum number of points you can get in this category if your program does effectively print out the table it was designed to do.
6. External Documentation This includes content in the User Manual, System Manual, and for this assignment the Test Log (via screen shots assembled into a PDF)
o 10 points = function definitions are commented with full explanation of purpose, parameters, results, and side effects, in the style of section 4.3 of the textbook "Function Comments".
o 8 points = good, but some significant missing information that would ordinarily be expected
o 4 points = needs significant improvement. Major miss. o 2 point = see the instructional staff to do better next time.
Academic Honesty
You must compose all written material yourself, including answers to book questions. All material taken from outside sources must be appropriately cited. If you need assistance with this aspect of the assignment, see a consultant during consulting hours.
To ensure that assignments are done independently, in addition to human observation, we will be running all assignments through a plagiarism detection system. This program uses compiler techniques which are invariant of syntax and style. It has a very high accuracy rate.
