Description

Function Templates

Workshop 9 (out of 10 marks – 3.75% of your final grade)

In this workshop, you are to define a global function in type-generic form.

LEARNING OUTCOMES
Upon successful completion of this workshop, you will have demonstrated your abilities to:
• code a function template
• implement a call to a templated function
• describe the syntax of a constrained cast and its purpose
• describe what you have learned in completing this workshop
SUBMISSION POLICY
All your work (all the files you create or modify) must contain your name, Seneca email and student number.
You are responsible to regularly back up your work.
LATE SUBMISSION PENALTIES:
• In-lab portion submitted late, with at-home portion: 0 for in-lab. Maximum of 7/10 for the entire workshop.
• If any of in-lab, at-home or reflection portions is missing, the mark for the workshop will be 0/10.
IN-LAB – TEMPLATED FUNCTIONS (60%)
As a secret agent, you have discovered the headquarters of an international supervillain, a mastermind of crime. In one room you come across an old USB flash drive containing FBI data on crime statistics in the USA. The data is in file crimedata.csv. There is some code to analyze the data in files ws9_lab.cpp, Data.h and Data.cpp. The program that you have found needs to be completed.
You suspect that the data is fake, but you need to prove it. You cannot transmit the data back to your own headquarters. They have instructed you to complete the program and to ask 4 questions. They will use your answers to authenticate the data. While reading the file records, you discover that some records contain integer data, and some records contain floating-point data.
INPUT FILE FORMAT:
The contents of file crimedata.csv are shown below. You can open the file in excel to show the columns in spreadsheet form.
5
Year,2000,2001,2002,2003,2004
Population,281421906,285317559,287973924,290788976,293656842
ViolentCrime,1425486,1439480,1423677,1383676,1360088
ViolentCrime_Rate,506.5,504.5,494.4,475.8,463.2
GrandTheftAuto,1160002,1228391,1246646,1261226,1237851
GrandTheftAuto_Rate,412.2,430.5,432.9,433.7,421.5
The first record has a single integer that holds the number of columns, n, of data in each record of the file. Each record, other than the first, contains a string (with no spaces) that describes the data in that record. The data in each record consists of n comma-separated numbers. These numbers can be integers or floating-point numbers.
The largest data value allowed in this file is 1,000,000,000. (1 billion, that is, 1 followed by 9 zeros). The smallest number allowed in this file is 0. The field width for output of each record’s description is 20. The field width for output of each data field in each record is 15.
The records with integer data are marked:
• Year
• Population
• ViolentCrime
• GrandTheftAuto
The records with floating-point data are marked:
• ViolentCrime_Rate
• GrandTheftAuto_Rate
The main() program reads the records in the order that they are in the file, one record at a time. The readRecord() function reads a single record. After reading all the data, the program displays the data and ask questions about it.

READROW FUNCTION:
The Data module includes two functions named readRow() with different signatures. Since both functions contain the same logic, you replace them with a single templated function of the same name, store the function template in Data.h, and remove the original function definitions from Data.cpp.

ANSWERS FUNCTION:
You need to complete the answers() function in Data.cpp. The code in it answers the following questions.
1. Print the total population growth from the beginning to the end of the data. (Hint: the beginning of the data is at population[0], and the end of the data is at population[n-1].
2. Between start and finish, did violent crime go up or down?
3. Print the average number of Grand Theft Auto incidents over all the years. Format it to show millions.
4. Print the minimum and maximum number of Violent Crime incidents.
Notes:
1. You can convert a double to an integer using static_cast<int>( ).
2. The average of an array of numbers is their sum divided by the number of items in the array.
OTHER FUNCTIONS:
Code the following functions as templated functions and store them in Data.h, along with your readRecord() templated function.
Function Prototypes
Return type Function name Template parameter Function Parameters
Functionality
T min T const T* data, int n Returns the smallest element in data
n is the number of elements in data
T max T const T* data, int n Returns the largest element in data
T sum T const T* data, int n Returns the sum of n elements in data
Double average T const T* data, int n Average is usually computed as a double in statistics because sometimes the average is a fraction between 2 integers. Note: the average of an array of n items is the sum of the items / n
Bool read T std::istream& input, T* data, int n Reads n comma-separated data elements from input. Returns true if successful, false otherwise.
Void display T const char* name, const T* data, int n Display name right-justified in a field of 20 and each data element in a field of 15

OUTPUT:
Your output should look like this

Year 2000 2001 2002 2003 2004
Population 281421906 285317559 287973924 290788976 293656842
ViolentCrime 1425486 1439480 1423677 1383676 1360088 ViolentCrimeRate 506.5 504.5 494.4 475.8 463.2
GrandTheftAuto 1160002 1228391 1246646 1261226 1237851 GrandTheftAutoRate 412.2 430.5 432.9 433.7 421.5
Population change from 2000 to 2004 is 12.23 million
Violent Crime trend is down
There are 1.23 million Grand Theft Auto incidents on average a year
The Minimum Violent Crime rate was 463
The Maximum Violent Crime rate was 506

IN-LAB SUBMISSION
To test and demonstrate execution of your program use the same data as the output example above.
If not on matrix already, upload Data.h, Data.cpp and w9_lab.cpp to your matrix account. Compile and run your code and make sure everything works properly.
Then run the following script from your account: (replace profname.proflastname with your professors Seneca userid)

~profname.proflastname/submit 244_w9_lab <ENTER>

and follow the instructions.
Please note that a successful submission does not guarantee full credit for this workshop.

AT-HOME (40%)
The at-home portion includes only the reflection.
REFLECTION:
1. What happens if you try to put your templated functions in Data.cpp? Does your source code compile if you move all functions to Data.h? Explain.
2. Move one templated function into ws9_lab.cpp. Does it work now? Do you need to define the template function above main(), before it is used, or can you define it below main()?
3. Could you have done this lab without templates, by just overloading your functions in Data.h to accept integer and double arguments? What is the advantage of using templates?
4. Are the following equivalent?
template<class T> template<typename T>
AT-HOME SUBMISSION
If not on matrix already, upload reflect.txt to your matrix account.
Then run the following script from your account: (replace profname.proflastname with your professors Seneca userid)

~profname.proflastname/submit 244_w9_home <ENTER>

and follow the instructions.

Please note that a successful submission does not guarantee full credit for this workshop.