ET 181. Purpose: The purpose of this lab is to become familiar with using arrays in C++.

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1 Lab: 8 TA: Bob Setlock ET 181 Purpose: The purpose of this lab is to become familiar with using arrays in C++. Perpetual Note: I suggest opening the following two files in their own windows for reference: Basic UNIX commands The vi editor Follow the instructions given on the ET181 Webpage: Laboratory 8 - Functions with Array Parameters The goal of this lab is to give you practice in developing functions with array parameters (Shiflet Section Functions with Array Parameters). We have chosen to base this exercise on an extension of program 'grades_array.cpp' in the chapter10 directory, in which we retrieved quiz grades from the 'grade.data' data file into the 'grade' array, and then used a function 'average' to evaluate the average value of the grades in the array. Consider the average summation as follows: As we saw previously (quiz 5), we use a for loop to convert a summation (Σ) into C++ code. Furthermore from Shiflet Section 10.1 we see that for n components of an array, the subscripts go from 0 through (n-1). Thus the function 'average' would be translated to C++ as follows:

2 FUNCTION to determine the average value of an integer array PRE: int array "grade" has n elements containing valid values n > 0 POST: the float average value of the n grades has been returned float average(int grade[], int n) int sum = 0; for(int i = 0; i < n; i++) sum += grade[i]; return static_cast<float>(sum)/n; Normally it is not sufficient to consider the average value when analyzing a set of grades, however we need to consider the "standard deviation" of the grades from the average as well. This value is denoted by the Greek letter σ (lower case "sigma") and is defined as follows: The program 'lab_array.cpp' is an extension of the program 'grades_array.cpp', in which you are required to develop the function 'sigma' to evaluate and return the standard deviation, and a function 'minmax' to determine and return the minimum and maximum values in the 'grade' array. To determine the minimum value refer to the example 'ex1004a.cpp', (Shiflet Example 10.4) in which the winning score of the golf game is the minimum score. Telnet: "condor" Reference Material lab_array.cpp lab_array - program "grade_array.cpp" gets grades from the "grade.data" file into an array, and then evaluates and displays the average grade. The purpose of this lab is to augment this program to evaluate and display the standard deviation and the minimum grade. PROGRAMMER: Dr.Iz (Urieli) - 10/16/03

3 AUGMENTED AND MODIFIED: (your name here - today's date) #include <iostream> #include <iomanip> #include <fstream> using namespace std; int getgrade(int grade[], int max); gets data from file, returns number of items read float average(int grade[], int n); returns average of n elements of grade ####################################################lab8######## you will find two function prototypes below, the first "stdev" will return the standard deviation from the average grade, and the second, a function to find the minimum and maximum values of the grade array. Your task is to complete the function definitions, and extend the main function to invoke these two functions and display their respective return values. ################################################################ float stdev(int grade[], int n, float avgrade); returns the standard deviation from the average grade (avgrade) void minmax(int y[], int n, int& ymin, int& ymax); returns minimum & maximum values in n elements of the y array int main() const int SIZE = 100; int grade[size], n, gmin, gmax; float avgrade, sigma; n = getgrade(grade, SIZE); if (n <= 0) cout << "no data read from file\n"; else avgrade = average(grade, n); cout << "the average grade is " << avgrade << endl; return 0; FUNCTION to get grade data from file to array

4 PROGRAMMER: Dr.Iz (Urieli) DATE: 11/30/02 PRE: grade array can contain a maximum of max elements POST: n components have been read from file to array the value of n has been returned int getgrade(int grade[], int max) int n = 0, agrade; ifstream gradefile("grade.data"); if(!gradefile) cout << "cannot find \"grade.data\"\n"; else cout << "\"grade.data\" file opened\n"; gradefile >> agrade; while((agrade >=0) && (n < max)) grade[n] = agrade; cout << "grade[" << n << "] = " << grade[n] << endl; n++; gradefile >> agrade; char ch; while(gradefile.get(ch)) cout << ch; gradefile.close(); return n; FUNCTION to determine the average value of an integer array PROGRAMMER: Dr.Iz (Urieli) DATE: 11/30/02 PRE: int array a has n elements containing valid values n > 0 POST: the float average value of grade array has been returned float average(int grade[], int n) int sum = 0; for(int i = 0; i < n; i++) sum += grade[i]; return static_cast<float>(sum) / n;

5 grade.data (trailer value) ############################# This file contains 5 typical quiz grades of an et181 class. ############################# ex10.04a.cpp Example 10.4 a. Program to read golf scores from the file "EX1003.dat" (no white space after last score) and then to print the winning score #include <iostream> #include <fstream> #include <iomanip> #include <cassert> using namespace std; const int MAX_NUM_PLAYERS = 100; maximum number of players int main() void readscoresfile(int score[], int& numplayers); prototypes int winner(const int score[], int numplayers); int tourneyscore[max_num_players], array of scores tourneynum; actual number of players readscoresfile(tourneyscore, tourneynum); cout << "The winning score is " << winner(tourneyscore, tourneynum) << ".\n"; return 0;

6 Function to read values for an array Pre: EX1003.dat is a file of golf scores. Post: score is an integer array of golf scores. numplayers is the number of golf scores. void readscoresfile(int score[], int& numplayers) ifstream golffile("ex1003.dat"); assert(golffile); read values for array score until end of file numplayers = 0; while ((numplayers < MAX_NUM_PLAYERS) && (golffile >> score[numplayers])) ++numplayers; print error message if too much data for array if (!golffile.eof()) cout << endl << "File contained more than " << MAX_NUM_PLAYERS << " scores." << endl << "Only the first " << MAX_NUM_PLAYERS << " scores will be processed." << endl; golffile.close(); Example 10.4a. Function to return the winning (minimum) score of a golf tournament Pre: score is a nonempty constant array of integer golf scores. numplayers is the number of values in score. Post: The winning score was returned. int winner(const int score[], int numplayers) int min; ongoing minimum in array min = score[0]; for (int player = 1; player < numplayers; ++player)

7 if (score[player] < min) min = score[player]; return min; ex10.04b.cpp Example 10.4 b. Program to read golf scores from the file "EX1003.dat" (no white space after last score) and to print the winning score and player number #include <iostream> #include <fstream> #include <iomanip> #include <cassert> using namespace std; const int MAX_NUM_PLAYERS = 100; maximum number of players int main() void readscoresfile(int scores[], int& numplayers); void winner(const int scores[], int numplayers, int& min, int& minplayer); int tourneyscore[max_num_players]; array of scores int tourneynum; actual number of players int winningscore; winning score int winningplayer; player number of winner readscoresfile(tourneyscore, tourneynum); winner(tourneyscore, tourneynum, winningscore, winningplayer); cout << "The winner is Player #" << winningplayer << " with a score of " << winningscore << ".\n"; return 0; void readscoresfile(int score[], int& numplayers) ifstream golffile("ex1003.dat"); assert(golffile);

8 read values for array score until end of file numplayers = 0; while ((numplayers < MAX_NUM_PLAYERS) && (golffile >> score[numplayers])) ++numplayers; print error message if too much data for array if (!golffile.eof()) cout << endl << "File contained more than " << MAX_NUM_PLAYERS << " scores." << endl << "Only the first " << MAX_NUM_PLAYERS << " scores will be processed." << endl; golffile.close(); Example 10.4b. Function to return the winning (minimum) score and player number of a golf tournament Pre: score is a nonempty constant array of integer golf scores with the minimum occurring only once. numplayers is the number of values in score. Post: The winning score (min) and player number (minplayer) were returned. void winner(const int score[], int numplayers, int& min, int& minplayer) min = score[0]; minplayer = 1; for (int player = 1; player < numplayers; ++player) if (score[player] < min) min = score[player]; minplayer = player + 1; Shiflet pages

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