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cpp/string/basic string/operator cmp: differenze tra le versioni

Da cppreference.com.
< cpp‎ | string‎ | basic string
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{{title|Operatori della classe string}}
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Sintassi:
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{{title |
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string}}
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<syntaxhighlight lang="cpp">
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    #include <string>
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    bool operator==(const string& c1, const string& c2);
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    bool operator!=(const string& c1, const string& c2);
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    bool operator<(const string& c1, const string& c2);
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    bool operator>(const string& c1, const string& c2);
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    bool operator<=(const string& c1, const string& c2);
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    bool operator>=(const string& c1, const string& c2);
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    string operator+(const string& s1, const string& s2 );
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    string operator+(const char* s, const string& s2 );
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    string operator+( char c, const string& s2 );
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    string operator+( const string& s1, const char* s );
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    string operator+( const string& s1, char c );
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    string& operator+=(const string& append);
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    string& operator+=(const char* append);
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    string& operator+=(const char  append);
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    ostream& operator<<( ostream& os, const string& s );
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    istream& operator>>( istream& is, string& s );
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    string& operator=( const string& s );
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    string& operator=( const char* s );
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    string& operator=( char ch );
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    char& operator[]( size_type index );
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    const char& operator[]( size_type index ) const;
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</syntaxhighlight>
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Le stringhe C++ possono essere comparate tra loro usando gli operatori di comparazione standard: ==, !=, <nowiki><=</nowiki>, >=, <, >, e =. Eseguire una comparazione o assegnare una stringa ad un altra richiede un tempo di esecuzione [[cpp/complexity | lineare]].
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di , === , , =.|.
  
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Due stringhe sono uguali se:
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# La loro dimensione e' la stessa, e
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# Ogni membro della prima stringa, posto nella i-esima posizione e' identico al membro della seconda stringa posto della medesima poisizione i.
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La comparazione fra due stringhe e' eseguita usando l'ordinamento Lessicografico.
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stringhe
  
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In aggiunta alle normali operazioni sui contenitori, le stringhe possono anche essere concatenate usando l'operatore + e
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stringhe |
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usate con le [[cpp/io | Classi I/O stream di C++]] utilizzando gli operatori <nowiki><< e >></nowiki> .
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Ad esempio, il seguente frammento di codice concatena due stringhe e visualizza la string a risultante:
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il di
  
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<syntaxhighlight lang="cpp">
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sono di o '
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  string s1 = "Now is the time...";
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  string s2 = "for all good men...";
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  string s3 = s1 + s2;
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  cout << "s3 is " << s3 << endl;
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</syntaxhighlight>
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In piu', alle stringhe possono essere assegnati valori che sono altre stringhe, vettori di caratteri o anche caratteri singoli. Il seguente codice e' perfettamente valido:
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<syntaxhighlight lang="cpp">
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  char ch = 'N';
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  string s;
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  s = ch;
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</syntaxhighlight>
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I singoli caratteri che compongono una stringa possono essere esaminati tramite l'operatore [], il quale ha tempo di esecuzione [[cpp/complexity | constante]].
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Argomenti correlati: [[cpp/string/basic_string/c_str | c_str]], [[cpp/string/basic_string/compare | compare]], [[cpp/string/basic_string/data | data]]
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[[en:cpp/string/basic string/operator cmp]]
 
[[en:cpp/string/basic string/operator cmp]]
 
[[es:cpp/string/basic string/operator cmp]]
 
[[es:cpp/string/basic string/operator cmp]]
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[[ja:cpp/string/basic string/operator cmp]]
 
[[ja:cpp/string/basic string/operator cmp]]
 
[[pl:cpp/string/basic string/operator cmp]]
 
[[pl:cpp/string/basic string/operator cmp]]

Versione attuale delle 15:10, 2 lug 2013

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C++
 
Stringhe libreria
Null-stringhe terminate
Original:
Null-terminated strings
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Byte stringhe
Multibyte stringhe
Stringhe larghe
Classi
Original:
Classes
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basic_string
char_traits
 
std::basic_string
Membri funzioni
Original:
Member functions
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basic_string::basic_string
basic_string::operator=
basic_string::assign
basic_string::get_allocator
Elemento accesso
Original:
Element access
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basic_string::at
basic_string::operator[]
basic_string::front(C++11)
basic_string::back(C++11)
basic_string::data
basic_string::c_str
Iteratori
Original:
Iterators
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basic_string::begin
basic_string::cbegin
(C++11)
basic_string::end
basic_string::cend
(C++11)
basic_string::rbegin
basic_string::crbegin
(C++11)
basic_string::rend
basic_string::crend
(C++11)
Capacità
Original:
Capacity
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basic_string::empty
basic_string::size
basic_string::length
basic_string::max_size
basic_string::reserve
basic_string::capacity
basic_string::shrink_to_fit(C++11)
Operazioni
Original:
Operations
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basic_string::clear
basic_string::insert
basic_string::erase
basic_string::push_back
basic_string::pop_back(C++11)
basic_string::append
basic_string::operator+=
basic_string::compare
basic_string::replace
basic_string::substr
basic_string::copy
basic_string::resize
basic_string::swap
Cerca
Original:
Search
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basic_string::find
basic_string::rfind
basic_string::find_first_of
basic_string::find_first_not_of
basic_string::find_last_of
basic_string::find_last_not_of
Costanti
Original:
Constants
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basic_string::npos
Non membri funzioni
Original:
Non-member functions
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operator+
operator==
operator!=
operator<
operator>
operator<=
operator>=
swap(std::basic_string)
operator<<
operator>>
getline
stoi
stol
stoll		(C++11)
(C++11)
(C++11)
stoul
stoull		(C++11)
(C++11)
stof
stod
stold		(C++11)
(C++11)
(C++11)
to_string(C++11)
to_wstring(C++11)
Helper classi
Original:
Helper classes
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hash<std::string>
hash<std::wstring>
hash<std::u32string>
hash<std::u16string>		(C++11)
 
template< class T, class Alloc >
bool operator==( basic_string<T,Alloc>& lhs, basic_string<T,Alloc>& rhs );
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template< class T, class Alloc >
bool operator!=( basic_string<T,Alloc>& lhs, basic_string<T,Alloc>& rhs );
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template< class T, class Alloc >
bool operator<( basic_string<T,Alloc>& lhs, basic_string<T,Alloc>& rhs );
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template< class T, class Alloc >
bool operator<=( basic_string<T,Alloc>& lhs, basic_string<T,Alloc>& rhs );
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template< class T, class Alloc >
bool operator>( basic_string<T,Alloc>& lhs, basic_string<T,Alloc>& rhs );
 (5)
template< class T, class Alloc >
bool operator>=( basic_string<T,Alloc>& lhs, basic_string<T,Alloc>& rhs );
 (6)
Confronta il contenuto di due stringhe.
Original:
Compares the contents of two strings.
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1-2)
Verifica se il contenuto di lhs e rhs sono uguali, cioè lhs.size() == rhs.size() e ogni carattere lhs ha carattere equivalente in rhs nella stessa posizione.
Original:
Checks if the contents of lhs and rhs are equal, that is, lhs.size() == rhs.size() and each character in lhs has equivalent character in rhs at the same position.
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3-6)
Confronta i contenuti di lhs e rhs lessicografico. Il confronto viene eseguito da una funzione equivalente a std::lexicographical_compare.
Original:
Compares the contents of lhs and rhs lexicographically. The comparison is performed by a function equivalent to std::lexicographical_compare.
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[modifica] Parametri

lhs, rhs -
stringhe il cui contenuto di confrontare
Original:
strings whose contents to compare
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[modifica] Valore di ritorno

1)
true se il contenuto delle stringhe sono equivalenti, false altrimenti
Original:
true if the contents of the strings are equivalent, false otherwise
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2)
true se il contenuto delle stringhe non sono equivalenti, false altrimenti
Original:
true if the contents of the strings are not equivalent, false otherwise
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3)
true se il contenuto del lhs sono lessicograficamente' meno rispetto ai contenuti di rhs, false altrimenti
Original:
true if the contents of the lhs are lexicographically less than the contents of rhs, false otherwise
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4)
true se il contenuto del lhs sono lessicograficamente' meno di o uguale' il contenuto di rhs, false altrimenti
Original:
true if the contents of the lhs are lexicographically less than or equal the contents of rhs, false otherwise
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5)
true se il contenuto del lhs sono lessicograficamente' maggiore rispetto ai contenuti di rhs, false altrimenti
Original:
true if the contents of the lhs are lexicographically greater than the contents of rhs, false otherwise
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6)
true se il contenuto del lhs sono lessicograficamente' maggiore di o uguale' il contenuto di rhs, false altrimenti
Original:
true if the contents of the lhs are lexicographically greater than or equal the contents of rhs, false otherwise
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[modifica] Complessità

Lineare nella dimensione delle corde.
Original:
Linear in the size of the strings.
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Estratto da "https://it.cppreference.com/mwiki/index.php?title=cpp/string/basic_string/operator_cmp&oldid=26714"