Strings
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Strings are specific constructs that are geared towards processing
sequences of characters
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before using include string header: #include <string>
don’t use string.h
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string declaration: string mystr;
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value assignment at declaration:
string mystr(“Hello”);
string mystr2=“Hello”;
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assignments from other types are not permitted:
string error1 = ‘c’; // error
string error2 = 22; // error
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can assign a character with assignment operator: mystr=‘n’;
Declaring strings
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String can be output as any other type:
string s=“hello world”;
cout << s << endl;
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two ways to input strings:
using extraction operator - strips white space and assigns the first
“word” to the string:
cin >> s;
hello wold\n input assigns only hello to s
using getline function - assigns all characters to string up to
newline (not included):
getline(cin, s);
hello wold\n input assigns hello world to s
do not mix one and the other way of input!
String I/O
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use assignment operator as with other types:
string s1, s2, s3;
s1=“Intro”;
s2=“OOP”;
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plus “+” is used for string concatenation: s3=s1 + “to” + s2;
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compound concatenation allowed: s1 += “duction”;
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characters can be concatenated with strings:
s2=“Hell” + ‘o’;
s2+=‘o’;
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no other types can be assigned to strings or concatenated with
strings:
s2= 42.54; // error
s2=“Catch” + 22; // error
String assignment and
concatenation
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Comparison operators (>, <, >=, <=, ==, !=) are applicable to strings
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strings are compared lexicographically:
string s1=“accept”, s2=“access”, s3=“acceptance”;
s1 is less than s2 and s1 is less than s3
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the order of symbols is determined by the symbol table (ASCII)
letters in the alphabet are in the increasing order
longer word (with the same characters) is greater than shorter
word
relying on other ASCII properties (e.g. capital letters are less than
small letters) is bad style
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comparisons to string constants and named constants are also legal:
const string myname=“John Doe”;
string hername=“Jane Doe”;
if ((myname==hername)||(myname==“Jake Doe”))
cout << “found him\n”;
Comparing strings
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A number of standard functions are defined for strings. Usual syntax:
string_name.function_name(arguments)
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Useful functions return string paremeters:
size() - current string size (number of characters currently
stored in string
length() - same as size
max_size() - maximum number of characters in string allowed
on this computer
empty() - true if string is empt y
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example:
string s=“Hello”;
cout << s.size();
outputs 5
String functions, string
characteristics
