1. 1 Object-Oriented Programming -- Using C++ Andres, Wen-Yuan Liao Department of Computer Science and Engineering De Lin Institute of Technology andres@dlit.edu.tw http://cse.dlit.edu.tw/~andres

2. 2 Chapter 5 - Pointers and Strings Outline 5.1 Introduction 5.2 Pointer Variable Declarations and Initialization 5.3 Pointer Operators 5.4 Calling Functions by Reference 5.5 Using const with Pointers 5.7 Pointer Expressions and Pointer Arithmetic 5.8 Relationship Between Pointers and Arrays 5.9 Arrays of Pointers 5.12 Introduction to Character and String Processing 5.12.1 Fundamentals of Characters and Strings 5.12.2 String Manipulation Functions of the String- Handling Library

3. 3 5.1Introduction Pointers –Powerful, but difficult to master –Simulate pass-by-reference –Close relationship with arrays and strings

4. 4 5.2Pointer Variable Declarations and Initialization Pointer variables –Contain memory addresses as values –Normally, variable contains specific value (direct reference) –Pointers contain address of variable that has specific value (indirect reference) Indirection –Referencing value through pointer Pointer declarations –* indicates variable is pointer int *myPtr; declares pointer to an int, pointer of type int * –Multiple pointers require multiple asterisks int *myPtr1, *myPtr2; count 7 countPtr count 7 intmyPtr

5. 5 5.2Pointer Variable Declarations and Initialization Can declare pointers to any data type Pointer initialization –Initialized to 0, NULL, or address 0 or NULL points to nothing

6. 6 5.3Pointer Operators & (address operator) –Returns memory address of its operand –Example int y = 5; int *yPtr; yPtr = &y; // yPtr gets address of y –yPtr “points to” y yPtr y 5 500000600000 y 5

7. 7 5.3Pointer Operators * (indirection/dereferencing operator) –Returns synonym for object its pointer operand points to –*yPtr returns y (because yPtr points to y ). –dereferenced pointer is lvalue *yptr = 9; // assigns 9 to y * and & are inverses of each other

8. Outline 8 fig05_04.cpp (1 of 2) 10 int a; // a is an integer 11 int *aPtr; // aPtr is a pointer to an integer 13 a = 7; 14 aPtr = &a; // aPtr assigned address of a 15 16 cout << "The address of a is " << &a 17 << "\nThe value of aPtr is " << aPtr; 18 19 cout << "\n\nThe value of a is " << a 20 << "\nThe value of *aPtr is " << *aPtr; 21 22 cout << "\n\nShowing that * and & are inverses of " 23 << "each other.\n&*aPtr = " << &*aPtr 24 << "\n*&aPtr = " << *&aPtr << endl; The address of a is 0012FED4 The value of aPtr is 0012FED4 The value of a is 7 The value of *aPtr is 7 Showing that * and & are inverses of each other. &*aPtr = 0012FED4 *&aPtr = 0012FED4 aPtr 12FED4 a 7

9. 9 5.4Calling Functions by Reference 3 ways to pass arguments to function –Pass-by-value –Pass-by-reference with reference arguments –Pass-by-reference with pointer arguments return can return one value from function Arguments passed to function using reference arguments –Modify original values of arguments –More than one value “returned”

10. 10 5.4Calling Functions by Reference Pass-by-reference with pointer arguments –Simulate pass-by-reference Use pointers and indirection operator –Pass address of argument using & operator –Arrays not passed with & because array name already pointer –* operator used as alias/nickname for variable inside of function

11. Outline 11 fig05_06.cpp (1 of 2) 1 // Fig. 5.6: fig05_06.cpp 2 // Cube a variable using pass-by-value. 3 #include 5 using std::cout; 6 using std::endl; 8 int cubeByValue( int ); // prototype 10 int main() 11 { 12 int number = 5; 14 cout << "The original value of number is " << number; 17 number = cubeByValue( number ); 19 cout << "\nThe new value of number is " << number << endl; 21 return 0; 23 } 25 26 int cubeByValue( int n ) 27 { 28 return n * n * n; // cube local variable n and return result 30 } The original value of number is 5 The new value of number is 125 5 number undefined n 5 125

12. Outline 12 fig05_07.cpp (1 of 2) 1 // Fig. 5.7: fig05_07.cpp 2 // Cube a variable using pass-by-reference 3 // with a pointer argument. 4 #include 6 using std::cout; 7 using std::endl; 9 void cubeByReference( int * ); // prototype 11 int main() 12 { 13 int number = 5; 14 15 cout << "The original value of number is " << number; 18 cubeByReference( &number ); 20 cout << "\nThe new value of number is " << number << endl; 22 return 0; 24 } 27 void cubeByReference( int *nPtr ) 28 { 29 *nPtr = *nPtr * *nPtr * *nPtr; // cube *nPtr 31 } The original value of number is 5 The new value of number is 125 5 number undefined nPtr 125

13. 13 5.5 Using const with Pointers const qualifier –Value of variable should not be modified –const used when function does not need to change a variable Principle of least privilege –Award function enough access to accomplish task, but no more Four ways to pass pointer to function –Nonconstant pointer to nonconstant data Highest amount of access data can be modified through the dereferenced pointer pointer can be modified to point to other data –Nonconstant pointer to constant data –Constant pointer to nonconstant data –Constant pointer to constant data Least amount of access

14. Outline 14 1 // Fig. 5.10: fig05_10.cpp 2 // Nonconstant pointer to nonconstant data 9 #include // prototypes for islower and toupper 11 void convertToUppercase( char * ); 13 int main() 14 { 15 char phrase[] = "characters and $32.98"; 17 cout << "The phrase before conversion is: " << phrase; 18 convertToUppercase( phrase ); 19 cout << "\nThe phrase after conversion is: " 20 << phrase << endl; 22 return 0; 24 } 27 void convertToUppercase( char *sPtr ) 28 { 29 while ( *sPtr != '\0' ) { // current character is not '\0' 31 if ( islower( *sPtr ) ) // if character is lowercase, 32 *sPtr = toupper( *sPtr ); // convert to uppercase 34 ++sPtr; // move sPtr to next character in string 36 } 38 } The phrase before conversion is: characters and $32.98 The phrase after conversion is: CHARACTERS AND $32.98 phrase sPtr c har…\0 CHAR

15. 15 5.5 Using const with Pointers Four ways to pass pointer to function –Nonconstant pointer to nonconstant data –Nonconstant pointer to constant data pointer can be modified to point to any data item data to which it points cannot be modified through that pointer –Constant pointer to nonconstant data –Constant pointer to constant data Least amount of access

16. Outline 16 fig05_11.cpp (1 of 2) 1 // Fig. 5.11: fig05_11.cpp 2 // Nonconstant pointer to constant data 4 #include 6 using std::cout; 7 using std::endl; 9 void printCharacters( const char * ); 11 int main() 12 { 13 char phrase[] = "print characters of a string"; 14 15 cout << "The string is:\n"; 16 printCharacters( phrase ); 17 cout << endl; 19 return 0; 21 } 25 void printCharacters( const char *sPtr ) 26 { 27 for ( ; *sPtr != '\0'; sPtr++ ) // no initialization 28 cout << *sPtr; 30 } The string is: print characters of a string phrase const char xPtr p rin…\0

17. Outline 17 fig05_12.cpp (1 of 1) fig05_12.cpp output (1 of 1) 1 // Fig. 5.12: fig05_12.cpp 2 // Nonconstant pointer to constant data 5 void f( const int * ); // prototype 7 int main() 8 { 9 int y; 11 f( &y ); // f attempts illegal modification 13 return 0; // indicates successful termination 15 } // end main 16 19 void f( const int *xPtr ) 20 { 21 *xPtr = 100; // error: cannot modify a const object 23 } // end function f d:\cpphtp4_examples\ch05\Fig05_12.cpp(21) : error C2166: l-value specifies const object y const int * xPtr 100

18. 18 5.5 Using const with Pointers Four ways to pass pointer to function –Nonconstant pointer to nonconstant data –Nonconstant pointer to constant data –Constant pointer to nonconstant data pointer always points to the same memory location data at that location can be modified through the pointer –Constant pointer to constant data Least amount of access

19. Outline 19 fig05_13.cpp (1 of 1) fig05_13.cpp output (1 of 1) 1 // Fig. 5.13: fig05_13.cpp 2 // Attempting to modify a constant pointer to 3 // non-constant data. 5 int main() 6 { 7 int x, y; 12 int * const ptr = &x; 13 14 *ptr = 7; // allowed: *ptr is not const 15 ptr = &y; // error: ptr is const; cannot assign new address 17 return 0; 19 } d:\cpphtp4_examples\ch05\Fig05_13.cpp(15) : error C2166: l-value specifies const object x y int * const ptr 7

20. 20 5.5 Using const with Pointers Four ways to pass pointer to function –Nonconstant pointer to nonconstant data –Nonconstant pointer to constant data –Constant pointer to nonconstant data –Constant pointer to constant data pointer always points to the same memory location data at that location cannot be modified using the pointer Least amount of access

21. Outline 21 fig05_14.cpp (1 of 1) 1 // Fig. 5.14: fig05_14.cpp 2 // Attempting to modify a constant pointer to constant data. 3 #include 5 using std::cout; 6 using std::endl; 8 int main() 9 { 10 int x = 5, y; 15 const int *const ptr = &x; 16 17 cout << *ptr << endl; 18 19 *ptr = 7; // error: *ptr is const; cannot assign new value 20 ptr = &y; // error: ptr is const; cannot assign new address 22 return 0; 24 } d:\cpphtp4_examples\ch05\Fig05_14.cpp(19) : error C2166: l-value specifies const object d:\cpphtp4_examples\ch05\Fig05_14.cpp(20) : error C2166: l-value specifies const object 5 const int x y int * const ptr 7

22. 22 5.5 Using const with Pointers const pointers –Always point to same memory location –Default for array name –Must be initialized when declared

23. 23 5.7Pointer Expressions and Pointer Arithmetic Pointer arithmetic –Increment/decrement pointer (++ or -- ) –Add/subtract an integer to/from a pointer( + or +=, - or -= ) –Pointers may be subtracted from each other –Pointer arithmetic meaningless unless performed on pointer to array 5 element int array on a machine using 4 byte int s –vPtr points to first element v[ 0 ], which is at location 3000 vPtr = 3000 –vPtr += 2 ; sets vPtr to 3008 vPtr points to v[ 2 ] pointer variable vPtr v[0]v[1]v[2]v[4]v[3] 30003004300830123016 location

24. 24 5.7Pointer Expressions and Pointer Arithmetic Subtracting pointers –Returns number of elements between two addresses vPtr2 = v[ 2 ]; vPtr = v[ 0 ]; vPtr2 - vPtr == 2 Pointer assignment –Pointer can be assigned to another pointer if both of same type –If not same type, cast operator must be used

25. 25 5.8Relationship Between Pointers and Arrays Arrays and pointers closely related –Array name like constant pointer –Pointers can do array subscripting operations Accessing array elements with pointers –Element b[ n ] can be accessed by *( bPtr + n ) Called pointer/offset notation –Addresses &b[ 3 ] same as bPtr + 3 –Array name can be treated as pointer b[ 3 ] same as *( b + 3 ) –Pointers can be subscripted (pointer/subscript notation) bPtr[ 3 ] same as b[ 3 ]

26. Outline 26 fig05_20.cpp (1 of 2) 1 // Fig. 5.20: fig05_20.cpp 11 int b[] = { 10, 20, 30, 40 }; 12 int *bPtr = b; // set bPtr to point to array b …… 18 for ( int i = 0; i < 4; i++ ) 19 cout << "b[" << i << "] = " << b[ i ] << '\n'; …… 26 for ( int offset1 = 0; offset1 < 4; offset1++ ) 27 cout << "*(b + " << offset1 << ") = " 28 << *( b + offset1 ) << '\n'; …… 33 for ( int j = 0; j < 4; j++ ) 34 cout << "bPtr[" << j << "] = " << bPtr[ j ] << '\n'; …… 39 for ( int offset2 = 0; offset2 < 4; offset2++ ) 40 cout << "*(bPtr + " << offset2 << ") = " 41 << *( bPtr + offset2 ) << '\n'; 43 return 0; 45 }

27. Outline 27 fig05_20.cpp output (1 of 1) Array b printed with: Array subscript notation b[0] = 10 b[1] = 20 b[2] = 30 b[3] = 40 Pointer/offset notation where the pointer is the array name *(b + 0) = 10 *(b + 1) = 20 *(b + 2) = 30 *(b + 3) = 40 Pointer subscript notation bPtr[0] = 10 bPtr[1] = 20 bPtr[2] = 30 bPtr[3] = 40 Pointer/offset notation *(bPtr + 0) = 10 *(bPtr + 1) = 20 *(bPtr + 2) = 30 *(bPtr + 3) = 40

28. Outline 28 fig05_21.cpp (1 of 2) 1 // Fig. 5.21: fig05_21.cpp …… 9 void copy1( char *, const char * ); // prototype 10 void copy2( char *, const char * ); // prototype 12 int main() 13 { 14 char string1[ 10 ]; 15 char *string2 = "Hello"; 16 char string3[ 10 ]; 17 char string4[] = "Good Bye"; 18 19 copy1( string1, string2 ); 20 cout << "string1 = " << string1 << endl; 21 22 copy2( string3, string4 ); 23 cout << "string3 = " << string3 << endl; 25 return 0; 27 }

29. Outline 29 fig05_21.cpp (2 of 2) fig05_21.cpp output (1 of 1) 30 void copy1( char *s1, const char *s2 ) 31 { 32 for ( int i = 0; ( s1[ i ] = s2[ i ] ) != '\0'; i++ ) 33 ; // do nothing in body 34 35 } 36 38 void copy2( char *s1, const char *s2 ) 39 { 40 for ( ; ( *s1 = *s2 ) != '\0'; s1++, s2++ ) 41 ; // do nothing in body 43 } string1 = Hello string3 = Good Bye

30. 30 5.9Arrays of Pointers Arrays can contain pointers –Commonly used to store array of strings char *suit[ 4 ] = {"Hearts", "Diamonds", "Clubs", "Spades" }; –Each element of suit points to char * (a string) –Array does not store strings, only pointers to strings –suit array has fixed size, but strings can be of any size suit[3] suit[2] suit[1] suit[0]’H’’e’’a’’r’’t’’s’ ’\0’ ’D’’i’’a’’m’’o’’n’’d’’s’ ’\0’ ’C’’l’’u’’b’’s’ ’\0’ ’S’’p’’a’’d’’e’’s’ ’\0’

31. 31 Exercises #2 3.11 3.16 (b), (e), (f) 3.53 4.6 4.7 4.18 5.9 (a), (b), (h), (i), (j) 5.22

32. 32 5.12.1 Fundamentals of Characters and Strings Character constant –Integer value represented as character in single quotes –'z' is integer value of z 122 in ASCII String –Series of characters treated as single unit –Can include letters, digits, special characters +, -, *... –String literal (string constants) Enclosed in double quotes, for example: "I like C++" –Array of characters, ends with null character '\0' –String is constant pointer Pointer to string’s first character –Like arrays

33. 33 5.12.1 Fundamentals of Characters and Strings String assignment –Character array char color[] = "blue"; –Creates 5 element char array color last element is '\0' –Variable of type char * char *colorPtr = "blue"; –Creates pointer colorPtr to letter b in string “blue” “blue” somewhere in memory –Alternative for character array char color[] = { ‘b’, ‘l’, ‘u’, ‘e’, ‘\0’ };

34. 34 5.12.1 Fundamentals of Characters and Strings Reading strings –Assign input to character array word[ 20 ] cin >> word Reads characters until whitespace or EOF String could exceed array size cin >> setw( 20 ) >> word; Reads 19 characters (space reserved for '\0' )

35. 35 5.12.1 Fundamentals of Characters and Strings cin.getline –Read line of text –cin.getline( array, size, delimiter ); –Copies input into specified array until either One less than size is reached delimiter character is input –Example char sentence[ 80 ]; cin.getline( sentence, 80, '\n' );

36. 36 5.12.2 String Manipulation Functions of the String-handling Library String handling library provides functions to –Manipulate string data –Compare strings –Search strings for characters and other strings –Tokenize strings (separate strings into logical pieces)

37. 37 5.12.2 String Manipulation Functions of the String-handling Library char *strcpy( char *s1, const char *s2 ); Copies the string s2 into the character array s1. The value of s1 is returned. First argument must be large enough to store string and terminating null character. char *strncpy( char *s1, const char *s2, size_t n ); Copies at most n characters of the string s2 into the character array s1. The value of s1 is returned. Does not necessarily copy terminating null character. char *strcat( char *s1, const char *s2 ); Appends the string s2 to the string s1. The first character of s2 overwrites the terminating null character of s1. The value of s1 is returned. Ensure first argument large enough to store concatenated result and null character. char *strncat( char *s1, const char *s2, size_t n ); Appends at most n characters of string s2 to string s1. The first character of s2 overwrites the terminating null character of s1. The value of s1 is returned. Appends terminating null character to result.

38. Outline 38 fig05_28.cpp (1 of 2) 12 char x[] = "Happy Birthday to You"; 13 char y[ 25 ]; 14 char z[ 15 ]; 16 strcpy( y, x ); // copy contents of x into y 22 strncpy( z, x, 14 ); // does not copy null character 23 z[ 14 ] = '\0'; // append '\0' to z's contents The string in array x is: Happy Birthday to You The string in array y is: Happy Birthday to You The string in array z is: Happy Birthday

39. Outline 39 fig05_29.cpp (1 of 2) 12 char s1[ 20 ] = "Happy "; 13 char s2[] = "New Year "; 14 char s3[ 40 ] = ""; 18 strcat( s1, s2 ); // concatenate s2 to s1 24 strncat( s3, s1, 6 ); // places '\0' after last character 29 strcat( s3, s1 ); // concatenate s1 to s3 s1 = Happy s2 = New Year After strcat(s1, s2): s1 = Happy New Year s2 = New Year After strncat(s3, s1, 6): s1 = Happy New Year s3 = Happy After strcat(s3, s1): s1 = Happy New Year s3 = Happy Happy New Year

40. 40 5.12.2 String Manipulation Functions of the String-handling Library int strcmp( const char *s1, const char *s2 ); Compares the string s1 with the string s2. The function returns a value of zero, less than zero or greater than zero if s1 is equal to, less than or greater than s2, respectively. Compares character by character. Strings compared using numeric codes. Character codes / character sets: ASCII (American Standard Code for Information Interchange) EBCDIC (Extended Binary Coded Decimal Interchange Code). int strncmp( const char *s1, const char *s2, size_t n ); Compares up to n characters of the string s1 with the string s2. The function returns zero, less than zero or greater than zero if s1 is equal to, less than or greater than s2, respectively. Stops comparing if reaches null character in one of arguments size_t strlen( const char *s ); Determines the length of string s. The number of characters preceding the terminating null character is returned.

41. Outline 41 fig05_30.cpp (1 of 2) 16 char *s1 = "Happy New Year"; 17 char *s2 = "Happy New Year"; 18 char *s3 = "Happy Holidays"; 22 strcmp( s1, s2 ); 24 strcmp( s1, s3 ); 25 strcmp( s3, s1 ); 28 strncmp( s1, s3, 6 ); 29 strncmp( s1, s3, 7 ); 31 strncmp( s3, s1, 7 ); s1 = Happy New Year s2 = Happy New Year s3 = Happy Holidays strcmp(s1, s2) = 0 strcmp(s1, s3) = 1 strcmp(s3, s1) = -1 strncmp(s1, s3, 6) = 0 strncmp(s1, s3, 7) = 1 strncmp(s3, s1, 7) = -1

42. Outline 42 fig05_32.cpp (1 of 1) 12 char *string1 = "abcdefghijklmnopqrstuvwxyz"; 13 char *string2 = "four"; 14 char *string3 = "Boston"; 17 strlen( string1 ); 19 strlen( string2 ); 21 strlen( string3 ); The length of "abcdefghijklmnopqrstuvwxyz" is 26 The length of "four" is 4 The length of "Boston" is 6

43. 43 18.9 Character-Handling Library Character Handling Library – –Functions to perform tests and manipulations on characters –Pass character as argument Character represented by an int –char does not allow negative values Characters often manipulated as int s EOF usually has value -1

44. 44 18.9 Character-Handling Library isalpha( int c ) Returns true if c is a letter (A-Z, a-z). Returns false otherwise. isdigit ( int c ) Returns true if digit (0-9). isalnum ( int c ) Returns true if letter or digit (A-Z, a-z, 0-9). isxdigit ( int c ) Returns true if hexadecimal digit (A-F, a-f, 0-9). islower ( int c ) Returns true if lowercase letter (a-z) isupper ( int c ) Returns true if uppercase letter (A-Z) int tolower ( int c ) If passed uppercase letter, returns lowercase letter ( A to a ). Otherwise, returns original argument int toupper ( int c ) As above, but turns lowercase letter to uppercase ( a to A ).

45. 45 18.9 Character-Handling Library isspace ( int c ) Returns true if space ' ', form feed '\f', newline '\n', carriage return '\r', horizontal tab '\t', vertical tab '\v' iscntrl ( int c ) Returns true if control character, such as tabs, form feed, alert ( '\a' ), backspace( '\b' ), carriage return, newline ispunct ( int c ) Returns true if printing character other than space, digit, or letter $ # ( ) [ ] { } ; : %, etc isprint ( int c ) Returns true if character can be displayed (including space) isgraph ( int c ) Returns true if character can be displayed, not including space

46. Outline 46 fig18_17.cpp (1 of 2) 1 // Fig. 18.17: fig18_17.cpp 13 << ( isdigit( '8' ) ? "8 is a" : "8 is not a" ) 15 << ( isdigit( '#' ) ? "# is a" : "# is not a" ) 19 << ( isalpha( 'A' ) ? "A is a" : "A is not a" ) 21 << ( isalpha( 'b' ) ? "b is a" : "b is not a" ) 23 << ( isalpha( '&' ) ? "& is a" : "& is not a" ) 25 << ( isalpha( '4' ) ? "4 is a" : "4 is not a" ) 29 << ( isalnum( 'A' ) ? "A is a" : "A is not a" ) 31 << ( isalnum( '8' ) ? "8 is a" : "8 is not a" ) 33 << ( isalnum( '#' ) ? "# is a" : "# is not a" ) 37 << ( isxdigit( 'F' ) ? "F is a" : "F is not a" ) 39 << ( isxdigit( 'J' ) ? "J is a" : "J is not a" ) 41 << ( isxdigit( '7' ) ? "7 is a" : "7 is not a" ) 43 << ( isxdigit( '$' ) ? "$ is a" : "$ is not a" ) 45 << ( isxdigit( 'f' ) ? "f is a" : "f is not a" )

47. Outline 47 fig18_17.cpp output (1 of 1) According to isdigit: 8 is a digit # is not a digit According to isalpha: A is a letter b is a letter & is not a letter 4 is not a letter According to isalnum: A is a digit or a letter 8 is a digit or a letter # is not a digit or a letter According to isxdigit: F is a hexadecimal digit J is not a hexadecimal digit 7 is a hexadecimal digit $ is not a hexadecimal digit f is a hexadecimal digit

48. Outline 48 fig18_18.cpp (1 of 2) 13 << ( islower( 'p' ) ? "p is a" : "p is not a" ) 15 << ( islower( 'P' ) ? "P is a" : "P is not a" ) 17 << ( islower( '5' ) ? "5 is a" : "5 is not a" ) 19 << ( islower( '!' ) ? "! is a" : "! is not a" ) 23 << ( isupper( 'D' ) ? "D is an" : "D is not an" ) 25 << ( isupper( 'd' ) ? "d is an" : "d is not an" ) 27 << ( isupper( '8' ) ? "8 is an" : "8 is not an" ) 29 << ( isupper( '$' ) ? "$ is an" : "$ is not an" ) 33 ( toupper( 'u' ) ) 35 ( toupper( '7' ) ) 37 ( toupper( '$' ) ) 39 ( tolower( 'L' ) ) << endl;

49. Outline 49 fig18_18.cpp (2 of 2) According to islower: p is a lowercase letter P is not a lowercase letter 5 is not a lowercase letter ! is not a lowercase letter According to isupper: D is an uppercase letter d is not an uppercase letter 8 is not an uppercase letter $ is not an uppercase letter u converted to uppercase is U 7 converted to uppercase is 7 $ converted to uppercase is $ L converted to lowercase is l

50. Outline 50 fig18_19.cpp (1 of 2) 13 << ( isspace( '\n' ) ? "is a" : "is not a" ) 15 << ( isspace( '\t' ) ? "is a" : "is not a" ) 17 << ( isspace( '%' ) ? "% is a" : "% is not a" ) 21 << ( iscntrl( '\n' ) ? "is a" : "is not a" ) 23 << ( iscntrl( '$' ) ? "$ is a" : "$ is not a" ) 27 << ( ispunct( ';' ) ? "; is a" : "; is not a" ) 29 << ( ispunct( 'Y' ) ? "Y is a" : "Y is not a" ) 31 << ( ispunct( '#' ) ? "# is a" : "# is not a" ) 35 << ( isprint( '$' ) ? "$ is a" : "$ is not a" ) 37 << ( isprint( '\a' ) ? "is a" : "is not a" ) 41 << ( isgraph( 'Q' ) ? "Q is a" : "Q is not a" ) 43 << ( isgraph( ' ' ) ? "is a" : "is not a" )

51. Outline 51 fig18_19.cpp output (1 of 1) According to isspace: Newline is a whitespace character Horizontal tab is a whitespace character % is not a whitespace character According to iscntrl: Newline is a control character $ is not a control character According to ispunct: ; is a punctuation character Y is not a punctuation character # is a punctuation character According to isprint: $ is a printing character Alert is not a printing character According to isgraph: Q is a printing character other than a space Space is not a printing character other than a space

52. 52 18.10 String-Conversion Functions String conversion functions –Convert to numeric values, searching, comparison – –Most functions take const char * Do not modify string

53. 53 18.10 String-Conversion Functions double atof( const char *nPtr ) Converts string to floating point number ( double ). Returns 0 if cannot be converted int atoi( const char *nPtr ) Converts string to integer. Returns 0 if cannot be converted long atol( const char *nPtr ) Converts string to long integer. If int and long both 4-bytes, then atoi and atol identical double strtod( const char *nPtr, char **endPtr ) Converts first argument to double, returns that value. Sets second argument to location of first character after converted portion of string strtod("123.4this is a test", &stringPtr); Returns 123.4. stringPtr points to "this is a test" long strtol( const char *nPtr, char **endPtr, int base ) Converts first argument to long, returns that value. Sets second argument to location of first character after converted portion of string. If NULL, remainder of string ignored. Third argument is base of value being converted. Any number 2 – 36. 0 specifies octal, decimal, or hexadecimal. long strtoul ( const char *nPtr, char **endPtr, int base ) As above, with unsigned long

54. Outline 54 fig18_21.cpp (1 of 1) fig18_21.cpp output (1 of 1) 1 // Fig. 18.21: fig18_21.cpp 12 double d = atof( "99.0" ); 14 cout << "The string \"99.0\" converted to double is " 15 << d << "\nThe converted value divided by 2 is " 16 << d / 2.0 << endl; The string "99.0" converted to double is 99 The converted value divided by 2 is 49.5 1 // Fig. 18.22: fig18_22.cpp 12 int i = atoi( "2593" ); 13 14 cout << "The string \"2593\" converted to int is " << i 15 << "\nThe converted value minus 593 is " << i - 593 16 << endl; The string "2593" converted to int is 2593 The converted value minus 593 is 2000

55. Outline 55 fig18_23.cpp (1 of 1) fig18_23.cpp output (1 of 1) 1 // Fig. 18.23: fig18_23.cpp 12 long x = atol( "1000000" ); 13 14 cout << "The string \"1000000\" converted to long is " << x 15 << "\nThe converted value divided by 2 is " << x / 2 16 << endl; The string "1000000" converted to long int is 1000000 The converted value divided by 2 is 500000

56. Outline 56 fig18_24.cpp (1 of 1) fig18_24.cpp output (1 of 1) 1 // Fig. 18.24: fig18_24.cpp 12 double d; 13 const char *string1 = "51.2% are admitted"; 14 char *stringPtr; 16 d = strtod( string1, &stringPtr ); 18 cout << "The string \"" << string1 19 << "\" is converted to the\ndouble value " << d 20 << " and the string \"" << stringPtr << "\"" << endl; The string "51.2% are admitted" is converted to the double value 51.2 and the string "% are admitted"

57. Outline 57 fig18_25.cpp (1 of 1) 12 long x; 13 const char *string1 = "-1234567abc"; 14 char *remainderPtr; 16 x = strtol( string1, &remainderPtr, 0 ); 18 cout << "The original string is \"" << string1 19 << "\"\nThe converted value is " << x 20 << "\nThe remainder of the original string is \"" 21 << remainderPtr 22 << "\"\nThe converted value plus 567 is " 23 << x + 567 << endl; The original string is "-1234567abc" The converted value is -1234567 The remainder of the original string is "abc" The converted value plus 567 is -1234000

58. Outline 58 fig18_26.cpp (1 of 1) 12 unsigned long x; 13 const char *string1 = "1234567abc"; 14 char *remainderPtr; 16 x = strtoul( string1, &remainderPtr, 0 ); 18 cout << "The original string is \"" << string1 19 << "\"\nThe converted value is " << x 20 << "\nThe remainder of the original string is \"" 21 << remainderPtr 22 << "\"\nThe converted value minus 567 is " 23 << x - 567 << endl; The original string is "1234567abc" The converted value is 1234567 The remainder of the original string is "abc" The converted value minus 567 is 1234000