1.  2003 Prentice Hall, Inc. All rights reserved. 1 Chapter 15 - Class string and String Stream Processing Outline 15.1 Introduction 15.2 string Assignment and Concatenation 15.3 Comparing strings 15.4 Substrings 15.5 Swapping strings 15.6 string Characteristics 15.7 Finding Strings and Characters in a string 15.8 Replacing Characters in a string 15.9 Inserting Characters into a string 15.10 Conversion to C-Style char * Strings 15.11 Iterators 15.12 String Stream Processing

2.  2003 Prentice Hall, Inc. All rights reserved. 2 15.1 Introduction Template class basic_string –String manipulation (copying, searching, etc.) typedef basic_string string; Also typedef for wchar_t –Include string initialization –string s1( "Hello" ); –string s2( 8, 'x' ); 8 'x' characters –string month = "March" Implicitly calls constructor

3.  2003 Prentice Hall, Inc. All rights reserved. 3 15.1 Introduction No conversion from int or char –The following definitions are errors string error1 = 'c'; string error2( 'u' ); string error3 = 22; string error4( 8 ); –However, can assign to one char if declared s = 'n';

4.  2003 Prentice Hall, Inc. All rights reserved. 4 15.1 Introduction string features –Not necessarily null terminated –length member function: s1.length() –Use [] to access individual characters: s1[0] 0 to length-1 –string not a pointer –Many member functions take start position and length If length argument too large, max chosen –Stream extraction cin >> stringObject; getline( cin, s) –Delimited by newline

5.  2003 Prentice Hall, Inc. All rights reserved. 5 15.2 string Assignment and Concatenation Assignment –s2 = s1; Makes a separate copy –s2.assign(s1); Same as s2 = s1; –myString.assign(s, start, N); Copies N characters from s, beginning at index start –Individual characters s2[0] = s3[2];

6.  2003 Prentice Hall, Inc. All rights reserved. 6 15.2 string Assignment and Concatenation Range checking –s3.at( index ); Returns character at index Can throw out_of_range exception –[] has no range checking Concatenation –s3.append( "pet" ); –s3 += "pet"; Both add "pet" to end of s3 –s3.append( s1, start, N ); Appends N characters from s1, beginning at index start

7.  2003 Prentice Hall, Inc. All rights reserved. Outline 7 fig15_01.cpp (1 of 3) 1 // Fig. 15.1: fig15_01.cpp 2 // Demonstrating string assignment and concatenation. 3 #include 4 5 using std::cout; 6 using std::endl; 7 8 #include 9 10 using std::string; 11 12 int main() 13 { 14 string string1( "cat" ); 15 string string2; 16 string string3; 17 18 string2 = string1; // assign string1 to string2 19 string3.assign( string1 ); // assign string1 to string3 20 cout << "string1: " << string1 << "\nstring2: " << string2 21 << "\nstring3: " << string3 << "\n\n"; 22 String initialization and assignment. Output string1: cat string2: cat string3: cat

8.  2003 Prentice Hall, Inc. All rights reserved. Outline 8 fig15_01.cpp (2 of 3) 23 // modify string2 and string3 24 string2[ 0 ] = string3[ 2 ] = 'r'; 25 26 cout << "After modification of string2 and string3:\n" 27 << "string1: " << string1 << "\nstring2: " << string2 28 << "\nstring3: "; 29 30 // demonstrating member function at 31 for ( int i = 0; i < string3.length(); i++ ) 32 cout << string3.at( i ); 33 34 // declare string4 and string5 35 string string4( string1 + "apult" ); 36 string string5; 37 38 // overloaded += 39 string3 += "pet"; // create "carpet" 40 string1.append( "acomb" ); // create "catacomb" 41 42 // append subscript locations 4 through end of string1 to 43 // create string "comb" (string5 was initially empty) 44 string5.append( string1, 4, string1.length() ); 45 46 cout << "\n\nAfter concatenation:\nstring1: " << string1 47 << "\nstring2: " << string2 << "\nstring3: " 48 << string3 << "\nstring4: " << string4 49 << "\nstring5: " << string5 << endl; 50 After modification of string2 and string3: string1: cat string2: rat string3: car Note use of member function at instead of []. After concatenation: string1: catacomb string2: rat string3: carpet string4: catapult string5: comb

9.  2003 Prentice Hall, Inc. All rights reserved. Outline 9 fig15_01.cpp (3 of 3) fig15_01.cpp output (1 of 1) string1: cat string2: cat string3: cat After modification of string2 and string3: string1: cat string2: rat string3: car After concatenation: string1: catacomb string2: rat string3: carpet string4: catapult string5: comb 51 return 0; 52 53 } // end main

10.  2003 Prentice Hall, Inc. All rights reserved. 10 15.3 Comparing strings Overloaded operators –==, !=,, = –Return bool s1.compare(s2) –Returns positive if s1 lexicographically greater Compares letter by letter 'B' lexicographically greater than 'A' –Returns negative if less, zero if equal –s1.compare(start, length, s2, start, length) Compare portions of s1 and s2 –s1.compare(start, length, s2) Compare portion of s1 with all of s2

11.  2003 Prentice Hall, Inc. All rights reserved. Outline 11 fig15_02.cpp (1 of 4) 1 // Fig. 15.2: fig15_02.cpp 2 // Demonstrating string comparison capabilities. 3 #include 4 5 using std::cout; 6 using std::endl; 7 8 #include 9 10 using std::string; 11 12 int main() 13 { 14 string string1( "Testing the comparison functions." ); 15 string string2( "Hello" ); 16 string string3( "stinger" ); 17 string string4( string2 ); 18

12.  2003 Prentice Hall, Inc. All rights reserved. Outline 12 fig15_02.cpp (2 of 4) 19 cout << "string1: " << string1 << "\nstring2: " << string2 20 << "\nstring3: " << string3 << "\nstring4: " << string4 21 << "\n\n"; 22 23 // comparing string1 and string4 24 if ( string1 == string4 ) 25 cout << "string1 == string4\n"; 26 else { // string1 != string4 27 if ( string1 > string4 ) 28 cout string4\n"; 29 else // string1 < string4 30 cout << "string1 < string4\n"; 31 } 32 33 // comparing string1 and string2 34 int result = string1.compare( string2 ); 35 36 if ( result == 0 ) 37 cout << "string1.compare( string2 ) == 0\n"; 38 else // result != 0 39 if ( result > 0 ) 40 cout 0\n"; 41 else // result < 0 42 cout << "string1.compare( string2 ) < 0\n"; 43 string1: Testing the comparison functions. string2: Hello string3: stinger string4: Hello string1 > string4 Note use of overloaded == operator.

13.  2003 Prentice Hall, Inc. All rights reserved. Outline 13 fig15_02.cpp (3 of 4) 44 // comparing string1 (elements 2-5) and string3 (elements 0-5) 45 result = string1.compare( 2, 5, string3, 0, 5 ); 46 47 if ( result == 0 ) 48 cout << "string1.compare( 2, 5, string3, 0, 5 ) == 0\n"; 49 else // result != 0 50 if ( result > 0 ) 51 cout 0\n"; 52 else // result < 0 53 cout << "string1.compare( 2, 5, string3, 0, 5 ) < 0\n"; 54 55 // comparing string2 and string4 56 result = string4.compare( 0, string2.length(), string2 ); 57 58 if ( result == 0 ) 59 cout << "string4.compare( 0, string2.length(), " 60 << "string2 ) == 0" << endl; 61 else // result != 0 62 if ( result > 0 ) 63 cout << "string4.compare( 0, string2.length(), " 64 0" << endl; 65 else // result < 0 66 cout << "string4.compare( 0, string2.length(), " 67 << "string2 ) < 0" << endl; 68 Note use of compare.

14.  2003 Prentice Hall, Inc. All rights reserved. Outline 14 fig15_02.cpp (4 of 4) fig15_02.cpp output (1 of 1) 69 // comparing string2 and string4 70 result = string2.compare( 0, 3, string4 ); 71 72 if ( result == 0 ) 73 cout << "string2.compare( 0, 3, string4 ) == 0" << endl; 74 else // result != 0 75 if ( result > 0 ) 76 cout 0" << endl; 77 else // result < 0 78 cout << "string2.compare( 0, 3, string4 ) < 0" << endl; 79 80 return 0; 81 82 } // end main string1: Testing the comparison functions. string2: Hello string3: stinger string4: Hello string1 > string4 string1.compare( string2 ) > 0 string1.compare( 2, 5, string3, 0, 5 ) == 0 string4.compare( 0, string2.length(), string2 ) == 0 string2.compare( 0, 3, string4 ) < 0

15.  2003 Prentice Hall, Inc. All rights reserved. 15 15.4 Substrings Function substr gets substring –s1.substr( start, N ); –Gets N characters, beginning with index start –Returns substring

16.  2003 Prentice Hall, Inc. All rights reserved. Outline 16 fig15_03.cpp (1 of 1) fig15_03.cpp output (1 of 1) 1 // Fig. 15.3: fig15_03.cpp 2 // Demonstrating string member function substr. 3 #include 4 5 using std::cout; 6 using std::endl; 7 8 #include 9 10 using std::string; 11 12 int main() 13 { 14 string string1( "The airplane landed on time." ); 15 16 // retrieve substring "plane" which 17 // begins at subscript 7 and consists of 5 elements 18 cout << string1.substr( 7, 5 ) << endl; 19 20 return 0; 21 22 } // end main plane Note usage of substr.

17.  2003 Prentice Hall, Inc. All rights reserved. 17 15.5 Swapping strings s1.swap(s2); –Switch contents of two strings

18.  2003 Prentice Hall, Inc. All rights reserved. Outline 18 fig15_04.cpp (1 of 1) 1 // Fig. 15.4: fig15_04.cpp 2 // Using the swap function to swap two strings. 3 #include 4 5 using std::cout; 6 using std::endl; 7 8 #include 9 10 using std::string; 11 12 int main() 13 { 14 string first( "one" ); 15 string second( "two" ); 16 17 // output strings 18 cout << "Before swap:\n first: " << first 19 << "\nsecond: " << second; 20 21 first.swap( second ); // swap strings 22 23 cout << "\n\nAfter swap:\n first: " << first 24 << "\nsecond: " << second << endl; 25 26 return 0; 27 28 } // end main Call swap.

19.  2003 Prentice Hall, Inc. All rights reserved. Outline 19 fig15_04.cpp output (1 of 1) Before swap: first: one second: two After swap: first: two second: one

20.  2003 Prentice Hall, Inc. All rights reserved. 20 15.6 string Characteristics Member functions –s1.size() and s1.length() Number of characters in string –s1.capacity() Number of elements that can be stored without reallocation –s1.max_size() Maximum possible string size –s1.empty() Returns true if empty –s1.resize(newlength) Resizes string to newlength

21.  2003 Prentice Hall, Inc. All rights reserved. Outline 21 fig15_05.cpp (1 of 3) 1 // Fig. 15.5: fig15_05.cpp 2 // Demonstrating member functions related to size and capacity. 3 #include 4 5 using std::cout; 6 using std::endl; 7 using std::cin; 8 using std::boolalpha; 9 10 #include 11 12 using std::string; 13 14 void printStatistics( const string & ); 15 16 int main() 17 { 18 string string1; 19 20 cout << "Statistics before input:\n" << boolalpha; 21 printStatistics( string1 ); 22 23 // read in "tomato" 24 cout << "\n\nEnter a string: "; 25 cin >> string1; // delimited by whitespace 26 cout << "The string entered was: " << string1;

22.  2003 Prentice Hall, Inc. All rights reserved. Outline 22 fig15_05.cpp (2 of 3) 27 28 cout << "\nStatistics after input:\n"; 29 printStatistics( string1 ); 30 31 // read in "soup" 32 cin >> string1; // delimited by whitespace 33 cout << "\n\nThe remaining string is: " << string1 << endl; 34 printStatistics( string1 ); 35 36 // append 46 characters to string1 37 string1 += "1234567890abcdefghijklmnopqrstuvwxyz1234567890"; 38 cout << "\n\nstring1 is now: " << string1 << endl; 39 printStatistics( string1 ); 40 41 // add 10 elements to string1 42 string1.resize( string1.length() + 10 ); 43 cout << "\n\nStats after resizing by (length + 10):\n"; 44 printStatistics( string1 ); 45 46 cout << endl; 47 return 0; 48 49 } // end main 50 Resize string.

23.  2003 Prentice Hall, Inc. All rights reserved. Outline 23 fig15_05.cpp (3 of 3) fig15_05.cpp output (1 of 2) 51 // display string statistics 52 void printStatistics( const string &stringRef ) 53 { 54 cout << "capacity: " << stringRef.capacity() 55 << "\nmax size: " << stringRef.max_size() 56 << "\nsize: " << stringRef.size() 57 << "\nlength: " << stringRef.length() 58 << "\nempty: " << stringRef.empty(); 59 60 } // end printStatistics Statistics before input: capacity: 0 max size: 4294967293 size: 0 length: 0 empty: true Enter a string: tomato soup The string entered was: tomato Statistics after input: capacity: 31 max size: 4294967293 size: 6 length: 6 empty: false Display various string characteristics.

24.  2003 Prentice Hall, Inc. All rights reserved. Outline 24 fig15_05.cpp output (2 of 2) The remaining string is: soup capacity: 31 max size: 4294967293 size: 4 length: 4 empty: false string1 is now: soup1234567890abcdefghijklmnopqrstuvwxyz1234567890 capacity: 63 max size: 4294967293 size: 50 length: 50 empty: false Stats after resizing by (length + 10): capacity: 63 max size: 4294967293 size: 60 length: 60 empty: false

25.  2003 Prentice Hall, Inc. All rights reserved. 25 15.7 Finding Strings and Characters in a string Find functions –If found, index returned –If not found, string::npos returned Public static constant in class string –s1.find( s2 ) –s1.rfind( s2 ) Searches right-to-left –s1.find_first_of( s2 ) Returns first occurrence of any character in s2 s1.find_frist_of( "abcd" ) –Returns index of first 'a', 'b', 'c' or 'd'

26.  2003 Prentice Hall, Inc. All rights reserved. 26 15.7 Finding Strings and Characters in a string Find functions –s1.find_last_of( s2 ) Finds last occurrence of any character in s2 –s1.find_first_not_of( s2 ) Finds first character NOT in s2 –s1.find_last_not_of( s2 ) Finds last character NOT in s2

27.  2003 Prentice Hall, Inc. All rights reserved. Outline 27 fig15_06.cpp (1 of 3) 1 // Fig. 15.6: fig15_06.cpp 2 // Demonstrating the string find member functions 3 #include 4 5 using std::cout; 6 using std::endl; 7 8 #include 9 10 using std::string; 11 12 int main() 13 { 14 string string1( "noon is 12 p.m." ); 15 int location; 16 17 // find "is" at location 5 18 cout << "Original string:\n" << string1 19 << "\n\n(find) \"is\" was found at: " 20 << string1.find( "is" ) 21 << "\n(rfind) \"is\" was found at: " 22 << string1.rfind( "is" ); 23 24 // find 'o' at location 1 25 location = string1.find_first_of( "misop" ); Find first occurrence of m, i, s, o or p. Note call to function find.

28.  2003 Prentice Hall, Inc. All rights reserved. Outline 28 fig15_06.cpp (2 of 3) 26 27 cout << "\n\n(find_first_of) found '" << string1[ location ] 28 << "' from the group \"misop\" at: " 29 << location; 30 31 // find 'm' at location 13 32 location = string1.find_last_of( "misop" ); 33 cout << "\n\n(find_last_of) found '" << string1[ location ] 34 << "' from the group \"misop\" at: " 35 << location; 36 37 // find '1' at location 8 38 location = string1.find_first_not_of( "noi spm" ); 39 cout << "\n\n(find_first_not_of) '" << string1[ location ] 40 << "' is not contained in \"noi spm\" and was found at:" 41 << location; 42 43 // find '.' at location 12 44 location = string1.find_first_not_of( "12noi spm" ); 45 cout << "\n\n(find_first_not_of) '" << string1[ location ] 46 << "' is not contained in \"12noi spm\" and was " 47 << "found at:" << location << endl; Calls to other find functions similar.

29.  2003 Prentice Hall, Inc. All rights reserved. Outline 29 fig15_06.cpp (3 of 3) fig15_06.cpp output (1 of 1) 48 49 // search for characters not in string1 50 location = string1.find_first_not_of( "noon is 12 p.m." ); 51 cout << "\nfind_first_not_of(\"noon is 12 p.m.\")" 52 << " returned: " << location << endl; 53 54 return 0; 55 56 } // end main Original string: noon is 12 p.m. (find) "is" was found at: 5 (rfind) "is" was found at: 5 (find_first_of) found 'o' from the group "misop" at: 1 (find_last_of) found 'm' from the group "misop" at: 13 (find_first_not_of) '1' is not contained in "noi spm" and was found at:8 (find_first_not_of) '.' is not contained in "12noi spm" and was found at:12 find_first_not_of("noon is 12 p.m.") returned: -1

30.  2003 Prentice Hall, Inc. All rights reserved. 30 15.8 Replacing Characters in a string s1.erase( start ) –Erase from index start to end of string, including start Replace –s1.replace( begin, N, s2) begin : index in s1 to start replacing N : number of characters to replace s2 : replacement string –s1.replace( begin, N, s2, index, num ) index : element in s2 where replacement begins num : number of elements to use when replacing –Replacement can overwrite characters –string::npos represents max string length

31.  2003 Prentice Hall, Inc. All rights reserved. Outline 31 fig15_07.cpp (1 of 2) 1 // Fig. 15.7: fig15_07.cpp 2 // Demonstrating string member functions erase and replace. 3 #include 4 5 using std::cout; 6 using std::endl; 7 8 #include 9 10 using std::string; 11 12 int main() 13 { 14 // compiler concatenates all parts into one string 15 string string1( "The values in any left subtree" 16 "\nare less than the value in the" 17 "\nparent node and the values in" 18 "\nany right subtree are greater" 19 "\nthan the value in the parent node" ); 20 21 cout << "Original string:\n" << string1 << endl << endl; 22 23 // remove all characters from (and including) location 62 24 // through the end of string1 25 string1.erase( 62 ); 26

32.  2003 Prentice Hall, Inc. All rights reserved. Outline 32 fig15_07.cpp (2 of 2) 27 // output new string 28 cout << "Original string after erase:\n" << string1 29 << "\n\nAfter first replacement:\n"; 30 31 // replace all spaces with period 32 int position = string1.find( " " ); 33 34 while ( position != string::npos ) { 35 string1.replace( position, 1, "." ); 36 position = string1.find( " ", position + 1 ); 37 } // end while 38 39 cout << string1 << "\n\nAfter second replacement:\n"; 40 41 // replace all periods with two semicolons 42 // NOTE: this will overwrite characters 43 position = string1.find( "." ); 44 45 while ( position != string::npos ) { 46 string1.replace( position, 2, "xxxxx;;yyy", 5, 2 ); 47 position = string1.find( ".", position + 1 ); 48 } // end while 49 50 cout << string1 << endl; 51 return 0; 52 53 } // end main Find each space and replace with a '.' Start each search at the next position. Replace all '.' with two semicolons (the two characters at index 5). string::npos represents max string length.

33.  2003 Prentice Hall, Inc. All rights reserved. Outline 33 fig15_07.cpp output (1 of 1) Original string: The values in any left subtree are less than the value in the parent node and the values in any right subtree are greater than the value in the parent node Original string after erase: The values in any left subtree are less than the value in the After first replacement: The.values.in.any.left.subtree are.less.than.the.value.in.the After second replacement: The;;alues;;n;;ny;;eft;;ubtree are;;ess;;han;;he;;alue;;n;;he

34.  2003 Prentice Hall, Inc. All rights reserved. 34 15.9 Inserting Characters into a string s1.insert( index, s2 ) –Inserts s2 before position index s1.insert( index, s2, index2, N ); –Inserts substring of s2 before position index –Substring is N characters, starting at index2

35.  2003 Prentice Hall, Inc. All rights reserved. Outline 35 fig15_08.cpp (1 of 2) 1 // Fig. 15.8: fig15_08.cpp 2 // Demonstrating class string insert member functions. 3 #include 4 5 using std::cout; 6 using std::endl; 7 8 #include 9 10 using std::string; 11 12 int main() 13 { 14 string string1( "beginning end" ); 15 string string2( "middle " ); 16 string string3( "12345678" ); 17 string string4( "xx" ); 18 19 cout << "Initial strings:\nstring1: " << string1 20 << "\nstring2: " << string2 << "\nstring3: " << string3 21 << "\nstring4: " << string4 << "\n\n"; 22 23 // insert "middle" at location 10 in string1 24 string1.insert( 10, string2 ); 25 Insert all of string2 before element 10.

36.  2003 Prentice Hall, Inc. All rights reserved. Outline 36 fig15_08.cpp (2 of 2) fig15_08.cpp output (1 of 1) 26 // insert "xx" at location 3 in string3 27 string3.insert( 3, string4, 0, string::npos ); 28 29 cout << "Strings after insert:\nstring1: " << string1 30 << "\nstring2: " << string2 << "\nstring3: " << string3 31 << "\nstring4: " << string4 << endl; 32 33 return 0; 34 35 } // end main Initial strings: string1: beginning end string2: middle string3: 12345678 string4: xx Strings after insert: string1: beginning middle end string2: middle string3: 123xx45678 string4: xx Insert all of string4 before index 3.

37.  2003 Prentice Hall, Inc. All rights reserved. 37 15.10 Conversion to C-Style char * Strings Conversion functions –string s not necessarily null-terminated –s1.copy( ptr, N, index ) Copies N characters into the array ptr Starts at location index Need to null terminate –s1.c_str() Returns const char * Null terminated –s1.data() Returns const char * NOT null-terminated

38.  2003 Prentice Hall, Inc. All rights reserved. Outline 38 fig15_09.cpp (1 of 2) 1 // Fig. 15.9: fig15_09.cpp 2 // Converting to C-style strings. 3 #include 4 5 using std::cout; 6 using std::endl; 7 8 #include 9 10 using std::string; 11 12 int main() 13 { 14 string string1( "STRINGS" ); 15 const char *ptr1 = 0; 16 int length = string1.length(); 17 char *ptr2 = new char[ length + 1 ]; // including null 18 19 // copy characters from string1 into allocated memory 20 string1.copy( ptr2, length, 0 ); 21 ptr2[ length ] = '\0'; // add null terminator 22 23 // output 24 cout << "string s is " << string1 25 << "\nstring1 converted to a C-Style string is " 26 << string1.c_str() << "\nptr1 is "; Note calls to copy and c_str.

39.  2003 Prentice Hall, Inc. All rights reserved. Outline 39 fig15_09.cpp (2 of 2) fig15_09.cpp output (1 of 1) 27 28 // Assign to pointer ptr1 the const char * returned by 29 // function data(). NOTE: this is a potentially dangerous 30 // assignment. If string1 is modified, pointer ptr1 can 31 // become invalid. 32 ptr1 = string1.data(); 33 34 // output each character using pointer 35 for ( int i = 0; i < length; i++ ) 36 cout << *( ptr1 + i ); // use pointer arithmetic 37 38 cout << "\nptr2 is " << ptr2 << endl; 39 delete [] ptr2; 40 return 0; 41 42 } // end main string s is STRINGS string1 converted to a C-Style string is STRINGS ptr1 is STRINGS ptr2 is STRINGS

40.  2003 Prentice Hall, Inc. All rights reserved. 40 15.11 Iterators Iterators –Forwards and backwards traversal of strings –Access to individual characters –Similar to pointer operations –More coverage Chapter 20

41.  2003 Prentice Hall, Inc. All rights reserved. 41 15.11 Iterators Basic usage –Creation string::const_iterator i = s.begin(); const, cannot modify string (more Chapter 20) –Referencing *i; // reference character ++i; // traverse one character forward –Test for end of string i != s.end() end returns iterator after last element of s

42.  2003 Prentice Hall, Inc. All rights reserved. Outline 42 fig15_10.cpp (1 of 1) 1 // Fig. 15.10: fig15_10.cpp 2 // Using an iterator to output a string. 3 #include 4 5 using std::cout; 6 using std::endl; 7 8 #include 9 10 using std::string; 11 12 int main() 13 { 14 string string1( "Testing iterators" ); 15 string::const_iterator iterator1 = string1.begin(); 16 17 cout << "string1 = " << string1 18 << "\n(Using iterator iterator1) string1 is: "; 19 20 // iterate through string 21 while ( iterator1 != string1.end() ) { 22 cout << *iterator1; // dereference iterator to get char 23 ++iterator1; // advance iterator to next char 24 } // end while 25 26 cout << endl; 27 return 0; 28 29 } // end main Print each character using the iterator.

43.  2003 Prentice Hall, Inc. All rights reserved. Outline 43 fig15_10.cpp output (1 of 1) string1 = Testing iterators (Using iterator iterator1) string1 is: Testing iterators

44.  2003 Prentice Hall, Inc. All rights reserved. 44 15.12 String Stream Processing I/O of strings to and from memory –Called in-memory I/O or string stream processing –Classes istringstream (input from string) ostringstream (output to a string) and headers –Use string formatting to save data to memory

45.  2003 Prentice Hall, Inc. All rights reserved. 45 15.12 String Stream Processing String output –Ostringstream outputString; –outputString << s1 << s2; –Member function str Returns string that was output to memory outputString.str()

46.  2003 Prentice Hall, Inc. All rights reserved. Outline 46 fig15_11.cpp (1 of 2) 1 // Fig. 15.11: fig15_11.cpp 2 // Using a dynamically allocated ostringstream object. 3 #include 4 5 using std::cout; 6 using std::endl; 7 8 #include 9 10 using std::string; 11 12 #include 13 14 using std::ostringstream; 15 16 int main() 17 { 18 ostringstream outputString; // create ostringstream instance 19 20 string string1( "Output of several data types " ); 21 string string2( "to an ostringstream object:" ); 22 string string3( "\n double: " ); 23 string string4( "\n int: " ); 24 string string5( "\naddress of int: " ); Create ostringstream object.

47.  2003 Prentice Hall, Inc. All rights reserved. Outline 47 fig15_11.cpp (2 of 2) 25 26 double double1 = 123.4567; 27 int integer = 22; 28 29 // output strings, double and int to outputString 30 outputString << string1 << string2 << string3 << double1 31 << string4 << integer << string5 << &integer; 32 33 // call str to output contents 34 cout << "outputString contains:\n" << outputString.str(); 35 36 // add additional characters and call str to output string 37 outputString << "\nmore characters added"; 38 cout << "\n\nafter additional stream insertions,\n" 39 << "outputString contains:\n" << outputString.str() 40 << endl; 41 42 return 0; 43 44 } // end main Output format just like to writing to cout.

48.  2003 Prentice Hall, Inc. All rights reserved. Outline 48 fig15_11.cpp output (1 of 1) outputString contains: Output of several data types to an ostringstream object: double: 123.457 int: 22 address of int: 0012FE94 after additional stream insertions, outputString contains: Output of several data types to an ostringstream object: double: 123.457 int: 22 address of int: 0012FE94 more characters added

49.  2003 Prentice Hall, Inc. All rights reserved. 49 15.12 String Stream Processing String input –istringstream inputString ( myString ); –inputString >> string1 >> string2 –Like reading from cin

50.  2003 Prentice Hall, Inc. All rights reserved. Outline 50 fig15_12.cpp (1 of 2) 1 // Fig. 15.12: fig15_12.cpp 2 // Demonstrating input from an istringstream object. 3 #include 4 5 using std::cout; 6 using std::endl; 7 8 #include 9 10 using std::string; 11 12 #include 13 14 using std::istringstream; 15 16 int main() 17 { 18 string input( "Input test 123 4.7 A" ); 19 istringstream inputString( input ); 20 string string1; 21 string string2; 22 int integer; 23 double double1; 24 char character; 25 Create and initialize istringstream object.

51.  2003 Prentice Hall, Inc. All rights reserved. Outline 51 fig15_12.cpp (2 of 2) 26 inputString >> string1 >> string2 >> integer >> double1 27 >> character; 28 29 cout << "The following items were extracted\n" 30 << "from the istringstream object:" 31 << "\nstring: " << string1 32 << "\nstring: " << string2 33 << "\n int: " << integer 34 << "\ndouble: " << double1 35 << "\n char: " << character; 36 37 // attempt to read from empty stream 38 long value; 39 40 inputString >> value; 41 42 // test stream results 43 if ( inputString.good() ) 44 cout << "\n\nlong value is: " << value << endl; 45 else 46 cout << "\n\ninputString is empty" << endl; 47 48 return 0; 49 50 } // end main Read data into variables. good returns 1 if can still read data (no EOF, bad bits, etc). In this case, there is no data, so the test fails.

52.  2003 Prentice Hall, Inc. All rights reserved. Outline 52 fig15_12.cpp output (1 of 1) The following items were extracted from the istringstream object: string: Input string: test int: 123 double: 4.7 char: A inputString is empty