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The string Class
Preprocessor directive
#include <string>
Declaration
string name; // creates string
object called name
string name = "character string"; //
itialization
Read in an entire line of input
getline(cin, name);
Assignment
string name, cartoon;
cartoon = "Fred Flintstone";
name = cartoon; // "Fred Flintone" assigned
to name
Subscript operation
characters in a string are indexed starting with 0.
name = "John D";
index 0
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index1
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index2
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index 3
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index 4
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index 5
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J
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o
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h
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n
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D
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Subscript operator [ ]
string_object[index]
example: name[3] = z;
Relational operators
<, >, <=, >=, ==, !=
Compares characters of two strings in order, until a match occurs.
The value of a character is its ASCII code.
Concatenation
Combines two strings into a single string using + symbol
string state = "Minnesota", team;
team = state + " Vikings"; // Assigns "Minnesota
Vikings" to team
The size() function
name.size() - returns the number of characters in the
string name
The empty() function
name.empty() - returns boolean value true if string is empty,
false otherwise
Substrings
Substring extraction:
string_object.substr(first, num_chars)
first
= first character in string to be selected
num_chars =
size to be selected
substr
returns a string object containing the substring.
string fullName = "Donald Duck", firstName, lastName;
firstName = fullName.substr(0, 6);
lastName = fullName.substr(7, 4);
Substring replacement:
string_object.replace(first, num_chars, replacement)
fullName.replace(0, 6, "Daisy");
// changes fullName to "Daisy Duck"
Substring removal:
string_object.erase()
// makes strin_object an empty string
string.object.erase(first, num_chars)
fullName.erase(6, 4);
// changes fullname to "Daisy "
Substring insertion:
string_object.insert(position, new_string)
fullName.insert(5, " Duck");
// puts " Duck" back into fullName
Substring pattern matching:
string_object.find(pattern, position) // look for pattern
starting at index position
find() returns the index (subscript) where the first character
of the substring is found.
If the substring is not found, the function will
return string::npos, a special constant (usually -1) .
position = fullName.find("Duck",
0); // assigns 6 to position
Example:
Find the positions of the character string "duck" in the quote "If it walks
like a duck, and quacks like a duck then it must be a duck."
// Find the locations of substrings in a string
# include <iostream>
using namespace std;
# include <string>
int main()
{
int position;
string quote, sub;
cout << "Enter a character string:\n";
getline(cin, quote);
cout << "Enter a substring:\n";
getline(cin, sub);
position = quote.find(sub, 0);
while( position != string::npos )
{
cout << "String found in position "
<< position << endl;
position = quote.find(sub, position + 1);
}
}
cswanson@exa (~/summer) % g++ str_duck1.cpp
cswanson@exa (~/summer) % a.out
Enter a character string:
If it walks like a duck, and quacks like a duck, then it must be a duck
Enter a substring:
duck
String found in position 19
String found in position 43
String found in position 67
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