Varianti

    floating point literal

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    <metanoindex/>

     
    C++
     
    Linguaggio C + +
    Temi generali
    Original:
    General topics
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    Controllo del flusso
    Original:
    Flow control
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    Dichiarazioni esecuzione condizionale
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    Conditional execution statements
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    Iterazione dichiarazioni
    Original:
    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
    Original:
    Types
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    decltype specifier (C++11)
    Specifiers
    Original:
    Specifiers
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    cv specificatori
    Durata di stoccaggio specificatori
    constexpr specificatore (C++11)
    specificatore auto (C++11)
    alignas specificatore (C++11)
    Inizializzazione
    Original:
    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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    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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    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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    Esempio

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

    Output: 

    1.23456e-65
1000
58
400