Mathematical Functions, Characters, and Strings. APSC 160 Chapter 4

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1 Mathematical Functins, Characters, and Strings APSC 160 Chapter 4 1

2 Objectives T slve mathematics prblems by using the C++ mathematical functins (4.2) T represent characters using the char type (4.3) T encde characters using ASCII cde (4.3.1) T read a character frm the keybard (4.3.2) T represent special characters using the escape sequences (4.3.3) T cast a numeric value t a character and cast a character t an integer (4.3.4) T cmpare and test characters (4.3.5) T test and cnvert characters using the C++ character functins (4.6) T cnvert a hexadecimal character t a decimal value (4.7) 2

3 Objectives T represent strings using the string type and intrduce bjects and instance functins (4.8) T use the subscript peratr fr accessing and mdifying characters in a string (4.8.1) T use the + peratr t cncatenate strings (4.8.2) T cmpare strings using the relatinal peratrs (4.8.3) T read strings frm the keybard (4.8.4) T frmat utput using stream manipulatrs (4.10) T read/write data frm/t a file (4.11) 3

4 Intrductin This chapter intrduces functins fr perfrming cmmn mathematical peratins Because strings are frequently used in prgramming, it is beneficial t intrduce them early s that yu can begin t use them t develp useful prgrams 4

5 Mathematical Functins A functin is a grup f statements that perfrms a specific task pw(a, b) functin t cmpute a b rand() functin t generate a randm number Header <cmath> declares a set f functins t cmpute cmmn mathematical peratins and transfrmatins This sectin intrduces trignmetric functins and expnent functins 5

6 Trignmetric Functins Assume PI is a cnstant with value , then: sin(0) returns 0.0 cs(pi / 6) returns sin(270 * PI / 180) returns -1.0 cs(pi / 2) returns 0 sin(pi / 6) returns 0.5 asin(0.5) returns (same as π/6) sin(pi / 2) returns 1.0 acs(0.5) returns (same as π/3) cs(0) returns 1.0 atan(1.0) returns (same as π/4) Functin sin(radians) cs(radians) tan(radians) asin(a) acs(a) atan(a) Descriptin Returns the trignmetric sine f an angle in radians Returns the trignmetric csine f an angle in radians Returns the trignmetric tangent f an angle in radians Returns the angle in radians fr the inverse f sine Returns the angle in radians fr the inverse f sine Returns the angle in radians fr the inverse f sine 6

7 Expnent Functins Assume E is a cnstant with value , then: exp(1.0) returns lg(e) returns 1.0 lg10(10.0) returns 1.0 pw(2.0, 3) returns 8.0 sqrt(4.0) returns 2.0 Functin Descriptin exp(x) Returns e raised t pwer f x (e x ) lg(x) Returns the natural lgarithm f x (ln(x) = lg e x) lg10(x) Returns the base 10 lgarithm f x (lg 10 x) pw(a, b) Returns a raised t the pwer f b (a b ) sqrt(x) Returns the square rt f x ( x) fr x >= 0 7

8 Runding Functins Examples: ceil(2.1) returns 3.0 ceil(2.0) returns 2.0 ceil(-2.0) returns -2.0 ceil(-2.1) returns -2.0 flr(2.1) returns 2.0 flr(2.0) returns 2.0 flr(-2.0) returns 2.0 flr(-2.1) returns -3.0 Functin ceil(x) flr(x) Descriptin x is runded up t its nearest integer. This integer is returned as a duble value x is runded dwn t its nearest integer. This integer is returned as a duble value 8

9 min, max, and abs Functins max and min are defined in algrithm and abs in cstdlib headers Examples: max(2, 3) returns 3 max(2.5, 3.0) returns 3.0 min(2.5, 4.6) returns 2.5 abs(-2) returns 2 abs(-2.1) returns 2.1 9

10 Character Data Type The character data type, char, is used t represent a single character A character literal is enclsed in single qutatin marks char letter = 'A'; //assigns character A t the char variable letter char numchar = '4'; //assigns digit character 4 t the char variable numchar A string literal must be enclsed in qutatin marks (" ") A character literal is a single character enclsed in single qutatin marks (' ') "A" is a string and 'A' is a character On mst systems, the size f the char type is 1 byte 10

11 Escape Sequences An escape sequence cnsists f a backslash (\) fllwed by a character r a cmbinatin f digits The characters ' ', '\t', '\f', '\r', and '\n' are knwn as the whitespace characters Escape Sequence Name \b Backspace \t Tab \n Linefeed \f Frmfeed \r Carriage Return \\ Backslash \ Duble Qute 11

12 Casting Char and Numeric Types When an integer is cast int a char, nly its lwer 8 bits f data are used; the ther part is ignred char c = 0XFF41; // The lwer 8 bits hex cde 41 is assigned t c cut << c; // variable c is character A When a flating-pint value is cast int a char, the flating-pint value is first cast int an int, which is then cast int a char char c = 65.25; // 65 is assigned t variable c cut << c; // variable c is character A When a char is cast int a numeric type, the character s ASCII is cast int the specified numeric type int i = 'A'; // The ASCII cde f character A is assigned t i cut << i; // variable i is 65 12

13 Casting Char and Numeric Types The char type is treated as if it were an integer f the byte size All numeric peratrs can be applied t char perands A char perand is autmatically cast int a number if the ther perand is a number r a character // The ASCII cde fr '2' is 50 and fr '3' is 51 int i = '2' + '3'; cut << "i is " << i << endl; int j = 2 + 'a'; // The ASCII cde fr 'a' is 97 cut << "j is " << j << endl; cut << j << " is the ASCII cde fr character " << static_cast<char>(j) << endl; The result is: i is 101 j is is the ASCII cde fr character c 13

14 T Uppercase 1 #include <istream> 2 using namespace std; 3 4 int main() 5 { 6 cut << "Enter a lwercase letter: "; 7 char lwercaseletter; 8 cin >> lwercaseletter; 9 10 char uppercaseletter = 11 static_cast<char>('a' + (lwercaseletter - 'a')); cut << "The crrespnding uppercase letter is " 14 << uppercaseletter << endl; return 0; 17 } 14

15 Character Functins Functin isdigit(ch) isalpha(ch) isalnum(ch) islwer(ch) isupper(ch) isspace(ch) tlwer(ch) tupper(ch) Descriptin Returns true if the specified character is a digit. Returns true if the specified character is a letter. Returns true if the specified character is a letter r digit. Returns true if the specified character is a lwercase letter. Returns true if the specified character is an uppercase letter. Returns true if the specified character is a whitespace character. Returns the lwercase f the specified character. Returns the uppercase f the specified character. 15

16 Hex t Decimal 1 #include <istream> 2 #include <cctype> 3 using namespace std; 4 5 int main() 6 { 7 cut << "Enter a hex digit: "; 8 char hexdigit; 9 cin >> hexdigit; hexdigit = tupper(hexdigit); 12 if (hexdigit <= 'F' && hexdigit >= 'A') 13 { 14 int value = 10 + hexdigit - 'A'; 15 cut << "The decimal value fr hex digit " 16 << hexdigit << " is " << value << endl; 17 } 16

17 Hex t Decimal 18 else if (isdigit(hexdigit)) 19 { 20 cut << "The decimal value fr hex digit " 21 << hexdigit << " is " << hexdigit << endl; 22 } 23 else 24 { 25 cut << hexdigit << " is an invalid input" << endl; 26 } return 0; 29 } 17

18 string Type The char type represents nly ne character T represent a string f characters, use the data type called string string message = "Prgramming is fun"; Include the <string> header file t use the string type Example string s = "Bttm"; cut << s.length() << endl; cut << s.at(0) << endl; cut << s.at(1) << endl; Functin length() size() at(index) Descriptin Returns the number f characters in this string. Same as length(). Returns the character at the specified index frm this string. 18

19 String Index and Subscript Operatr The index fr the first character in the string is 0 The subscript peratr t access the character at a specified index in a string stringname[index] string s = "ABCD"; s[0] = 'P'; //replaces A cut << s[0] << endl; //displays P cut << s[1] << endl; //displays B The + and += peratrs are used fr cncatenating tw strings string s3 = s1 + s2; string message = "Welcme t C++" message += " and prgramming is fun"; string s = "ABC"; s += 'D'; //The new s is "ABCD" 19

20 Cmparing Strings Relatinal peratrs are used t cmpare tw strings by cmparing their crrespnding characters ne by ne frm left t right string s1 = "ABC"; string s2 = "ABE"; cut << (s1 == s2) << endl; // Displays 0 (means false) cut << (s1!= s2) << endl; // Displays 1 (means true) cut << (s1 > s2) << endl; // Displays 0 (means false) cut << (s1 >= s2) << endl; // Displays 0 (means false) cut << (s1 < s2) << endl; // Displays 1 (means true) cut << (s1 <= s2) << endl; // Displays 1 (means true) 20

$in the string header file, reads a string frm the keybard using the fllwing syntax: getline(cin, s, delimitcharacter) string city; cut << "Enter a city: "; getline(cin, city, '\n'); // Same as$

21 Reading Strings A string can be read frm the keybard using the cin bject string city; cut << "Enter a city: "; cin >> city; // Read t string city cut << "Yu entered " << city << endl; getline functin in the string header file, reads a string frm the keybard using the fllwing syntax: getline(cin, s, delimitcharacter) string city; cut << "Enter a city: "; getline(cin, city, '\n'); // Same as getline(cin, city) cut << "Yu entered " << city << endl; 21

22 Frmatting Cnsle Output Yu can use the stream manipulatrs t display frmatted utput n the cnsle Frmatting functins are called stream manipulatrs and are included in the imanip header file Example duble amunt = ; duble interestrate = ; duble interest = amunt * interestrate; cut << "Interest is " << fixed << setprecisin(2) << interest << endl; //displays

23 Stream Manipulatrs Operatr setprecisin(n) fixed shwpint setw(width) left right Descriptin sets the precisin f a flating-pint number displays flating-pint numbers in fixed-pint ntatin causes a flating-pint number t be displayed with a decimal pint with trailing zers even if it has n fractinal part specifies the width f a print field justifies the utput t the left justifies the utput t the right 23

24 Stream Manipulatrs setprecisin(n) specifies the ttal number f digits displayed fr a flatingpint number duble number = ; cut << setprecisin(3) << number << " " << setprecisin(4) << number << " " << setprecisin(5) << number << " " << setprecisin(6) << number << endl; displays setprecisin remains in effect until the precisin is changed duble number = ; cut << setprecisin(3) << number << " "; cut << << " " << << " " << << endl; displays

25 Stream Manipulatrs fixed frces the number t be displayed in nnscientific ntatin with a fixed number f digits after the decimal pint (default is 6) cut << fixed << ; displays Instead f e+08 Use setprecisin(n) after fixed t specify the number f digits after decimal pint duble mnthlypayment = ; duble ttalpayment = ; cut << fixed << setprecisin(2) << mnthlypayment << endl << ttalpayment << endl; displays

26 Stream Manipulatrs shwpint tgether with the setprecisin is used t frce the flating-pint numbers t be displayed with a decimal pint and a fixed number f digits after the decimal pint cut << setprecisin(6); cut << 1.23 << endl; cut << shwpint << 1.23 << endl; cut << shwpint << << endl; displays

27 Stream Manipulatrs cut uses just the number f the psitins needed fr an utput setw(width) is used t specify the minimum number f clumns fr an utput cut << setw(8) << "C++" << setw(6) << 101 << endl; cut << setw(8) << "Java" << setw(6) << 101 << endl; cut << setw(8) << "HTML" << setw(6) << 101 << endl; displays 8 6 C Java 101 HTML 101 If an item requires mre spaces than the specified width, the width is autmatically increased cut << setw(8) << "Prgramming " << setw(2) << 101; displays Prgramming

28 Stream Manipulatrs The left manipulatr is used t left-justify the utput and the right manipulatr is used t right-justify the utput cut << right; cut << setw(8) << 1.23 << endl; cut << setw(8) << << endl; displays cut << left; cut << setw(8) << 1.23 << endl; cut << setw(8) << << endl; displays

29 Simple File Input and Output Yu can save data t a file and read data frm the file T write data t a file, first declare a variable f the fstream type fstream utput; T specify a file, invke the pen functin frm utput bject utput.pen("numbers.txt"); This statement creates a file named numbers.txt Or create a file utput bject and pen the file in ne statement fstream utput("numbers.txt"); After yu are dne with the file, invke the clse functin utput.clse(); 29

30 Simple File Input and Output T read data frm a file, first declare a variable f the ifstream type ifstream input; T specify a file, invke the pen functin frm input input.pen("numbers.txt"); This statement pens a file named numbers.txt The file shuld be in the wrking directry (alng with the surce file) Or create a file input bject and pen the file in ne statement ifstream input("numbers.txt"); After yu are dne with the file, invke the clse functin input.clse(); 30

31 Simple File Output 1 #include <istream> 2 #include <fstream> 3 using namespace std; 4 5 int main() 6 { 7 fstream utput; 8 9 // Create a file 10 utput.pen("numbers.txt"); // Write numbers 13 utput << 95 << " " << 56 << " " << 34; // clse file 16 utput.clse(); cut << "Dne" << endl; return 0; 21 } 31

32 Simple File Input 1 #include <istream> 2 #include <fstream> 3 using namespace std; 4 5 int main() 6 { 7 ifstream input; 8 9 // Open a file 10 input.pen("numbers.txt"); int scre1, scre2, scre3; // Read data 15 input >> scre1; 16 input >> scre2; 17 input >> scre3; cut << "Ttal scre is " << scre1+scre2+scre3 << endl; // Clse file 22 input.clse(); cut << "Dne" << endl; return 0; 27 } 32

CS1150 Principles of Computer Science Math Functions, Characters and Strings

CS1150 Principles of Computer Science Math Functions, Characters and Strings CS1150 Principles f Cmputer Science Math Functins, Characters and Strings Yanyan Zhuang Department f Cmputer Science http://www.cs.uccs.edu/~yzhuang CS1150 UC. Clrad Springs Mathematical Functins Java