Programming Fundamentals/String Examples C++

Strings

 #include <algorithm>
 #include <iostream>
 #include <string>
 
 using namespace std;
 
 string toLower(string);
 string toUpper(string);
 
 int main() {
     string str = "Hello";
 
     cout << "string: " << str << endl;
     cout << "tolower: " << toLower(str) << endl;
     cout << "toupper: " << toUpper(str) << endl;
     cout << "string.find('e'): " << str.find('e') << endl;
     cout << "string.length(): " << str.length() << endl;
     cout << "string.replace(0, 1, \"j\"): " << str.replace(0, 1, "j") << endl;
     cout << "string.substr(2, 2): " << str.substr(2, 2) << endl;
 
     string name = "Bob";
     double value = 123.456;
     cout << name << " earned $" << fixed << setprecision (2) << value << endl;
 
 }
 
 string toLower(string str) {
     transform(str.begin(), str.end(), str.begin(), ::tolower);
 
     return str;
 }
 
 string toUpper(string str) {
     transform(str.begin(), str.end(), str.begin(), ::toupper);
 
     return str;
 }

Output

string: Hello
tolower: hello
toupper: HELLO
string.find('e'): 1
string.length(): 5
string.replace(0, 1, "j"): jello
string.substr(2, 2): ll
Bob earned $123.46

Files

 // This program creates a file, adds data to the file, displays the file,
 // appends more data to the file, displays the file, and then deletes the file.
 // It will not run if the file already exists.
 //
 // References:
 //     https://www.mathsisfun.com/temperature-conversion.html
 //     https://en.wikibooks.org/wiki/C%2B%2B_Programming
 
 #include <fstream>
 #include <iomanip>
 #include <iostream>
 #include <string>
 
 using namespace std;
 
 double calculateFahrenheit(double celsius);
 void createFile(string);
 void readFile(string);
 void appendFile(string);
 void deleteFile(string);
 int fileExists(string);
 
 int main() {
     string FILENAME = "~file.txt";
 
     if(fileExists(FILENAME)) {
         cout << "File already exists." << endl;
     } else {
         createFile(FILENAME);
         readFile(FILENAME);
         appendFile(FILENAME);
         readFile(FILENAME);
         deleteFile(FILENAME);
     }
 }
 
 double calculateFahrenheit(double celsius) {
     double fahrenheit;
 
     fahrenheit = celsius * 9 / 5 + 32;
     return fahrenheit;
 }
 
 void createFile(string filename) {
     fstream file;
     float celsius;
     float fahrenheit;
     
     file.open(filename, fstream::out);
     if (file.is_open()) {
         file << "Celsius,Fahrenheit\n";
         for(celsius = 0; celsius <= 50; celsius++) {
             fahrenheit = calculateFahrenheit(celsius);
             file << fixed << setprecision (1) << celsius << "," << fahrenheit << endl;
         }
         file.close();
     } else {
         cout << "Error creating " << filename << endl;
     }
 }
 
 void readFile(string filename)
 {
     fstream file;
     string line;
 
     file.open(filename, fstream::in);
     if (file.is_open()) {
         while (getline(file, line))
         {
             cout << line << endl;
         }
         file.close();
         cout << endl;
     } else {
         cout << "Error reading " << filename << endl;
     }
 }
 
 void appendFile(string filename)
 {
     fstream file;
     float celsius;
     float fahrenheit;
     
     file.open(filename, fstream::out | fstream::app);
     if (file.is_open()) {
         for(celsius = 51; celsius <= 100; celsius++) {
             fahrenheit = calculateFahrenheit(celsius);
             file << fixed << setprecision (1) << celsius << "," << fahrenheit << endl;
         }
         file.close();
     } else {
         cout << "Error appending to " << filename << endl;
     }
 }
 
 void deleteFile(string filename)
 {
     remove(filename.c_str());
 }
 
 int fileExists(string filename)
 {
     FILE *file;
     
     file = fopen (filename.c_str(), "r");
     if (file != NULL)
     {
         fclose (file);
     }
     return (file != NULL);
 }

Output

Celsius,Fahrenheit
0.0,32.0
1.0,33.8
2.0,35.6
...
98.0,208.4
99.0,210.2
100.0,212.0

References

• Wikiversity: Computer Programming

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