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floating point literal

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C++
 
Linguaggio C + +
Temi generali
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General topics
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Controllo del flusso
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Flow control
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Dichiarazioni esecuzione condizionale
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Conditional execution statements
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Iterazione dichiarazioni
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Iteration statements
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Vai dichiarazioni
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Jump statements
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Funzioni
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Functions
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dichiarazione di funzione
lambda funzione dichiarazione
funzione di modello
specificatore inline
eccezioni specifiche (deprecato)
noexcept specificatore (C++11)
Eccezioni
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Exceptions
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Spazi dei nomi
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Namespaces
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Tipi
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Types
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decltype specifier (C++11)
Specifiers
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Specifiers
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cv specificatori
Durata di stoccaggio specificatori
constexpr specificatore (C++11)
specificatore auto (C++11)
alignas specificatore (C++11)
Inizializzazione
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Initialization
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Letterali
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Literals
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Espressioni
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Expressions
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rappresentazioni alternative
Utilities
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Utilities
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Tipi
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Types
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typedef declaration
Tipo alias dichiarazione (C++11)
attributi (C++11)
Lancia
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Casts
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conversioni implicite
const_cast conversion
static_cast conversion
dynamic_cast conversion
reinterpret_cast conversion
Fusione C-stile e funzionale
Occupazione della memoria
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Memory allocation
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Classi
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Classes
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Specifiche per una classe di funzioni proprietà
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Class-specific function properties
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esplicito (C++11)
statico
Funzioni membro speciali
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Special member functions
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Modelli
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Templates
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classe template
funzione di modello
modello di specializzazione
parametri confezioni (C++11)
Varie
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Miscellaneous
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Montaggio in linea
 
Virgola mobile letterale definisce in fase di compilazione costante il cui valore è specificato nel file di origine.
Original:
Floating point literal defines a compile-time constant whose value is specified in the source file.
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[modifica] Sintassi

A virgola mobile letterali hanno due sintassi. Il primo è costituito dalle seguenti parti:
Original:
A floating-point literals have two syntaxes. The first one consists of the following parts:
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  • sequenza di cifre decimali non vuoto contenenti un carattere punto decimale (definisce significativo)
    Original:
    nonempty sequence of decimal digits containing a decimal point character (defines significant)
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  • (opzionale) e o E seguito con meno opzionali o segno più e la sequenza non vuota di cifre decimali (definisce esponente)
    Original:
    (opzionale) e or E followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent)
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  • (opzionale) uno specificatore di tipo suffisso come l, f, L o F
    Original:
    (opzionale) a suffix type specifier as a l, f, L or F
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La seconda è costituita dalle seguenti parti:
Original:
The second one consists of the following parts:
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  • sequenza non vuota di cifre decimali (definisce significativo)
    Original:
    nonempty sequence of decimal digits (defines significant)
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  • e o E seguito con meno opzionali o segno più e la sequenza non vuota di cifre decimali (definisce esponente)
    Original:
    e or E followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent)
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  • (opzionale) uno specificatore di tipo suffisso come l, f, L o F
    Original:
    (opzionale) a suffix type specifier as a l, f, L or F
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Il suffisso specificatore di tipo definisce il tipo effettivo della virgola mobile letterale:
Original:
The suffix type specifier defines the actual type of the floating-point literal:
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  • (Nessun suffisso) definisce double
    Original:
    (no suffix) defines double
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  • f F definisce float
    Original:
    f F defines float
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  • l L definisce long double
    Original:
    l L defines long double
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[modifica] Spiegazione

Una notazione decimale scientifica è utilizzato, il che significa che l'esponente è la potenza di 10 con la quale la multiplied.
è significativo
Original:
A decimal scientific notation is used, meaning that the exponent is the power of 10 by which the significant is multiplied.
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Il significato matematico di 123e4 è 123 × 10 4 </ sup>
Original:
The mathematical meaning of 123e4 is 123×104
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</div>

[modifica] Esempio

std::cout << 123.456e-67 << '\n'
          << .1E4f       << '\n'
          << 58.         << '\n'
          << 4e2         << '\n';

Output: 

1.23456e-65
1000
58
400
Estratto da "https://it.cppreference.com/mwiki/index.php?title=cpp/language/floating_literal&oldid=19233"