Varianti

    std::atof

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    <metanoindex/>

     
    C++
     
    Stringhe libreria
    Null-stringhe terminate
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    Null-terminated strings
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    Byte stringhe
    Multibyte stringhe
    Stringhe larghe
    Classi
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    Classes
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    basic_string
    char_traits
     
    Null-stringhe terminate byte
    Funzioni
    Original:
    Functions
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    Carattere manipolazione
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    Character manipulation
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    Le conversioni in formati numerici
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    Conversions to numeric formats
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    Della gestione delle stringhe
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    String manipulation
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    strcpy
    strncpy
    strcat
    strncat
    strxfrm
    String esame
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    String examination
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    Memoria manipolazione
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    Memory manipulation
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    memchr
    memcmp
    memset
    memcpy
    memmove
    Varie
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    Miscellaneous
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    strerror
     
    <tbody> </tbody>
    Elemento definito nell'header <cstdlib>
    double atof( const char *str );
    Interpreta un valore in virgola mobile in una stringa di byte puntato da str.
    Original:
    Interprets an floating point value in a byte string pointed to by str.
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    Funzione scarta eventuali spazi bianchi (come determinato dal std::isspace()) fino al primo carattere non-spazio si trova. Poi ci vuole come numero possibile di caratteri in modo da formare una valida rappresentazione in virgola mobile e li converte in valore in virgola mobile. Il valore di virgola mobile valido può essere uno dei seguenti:
    Original:
    Function discards any whitespace characters (as determined by std::isspace()) until first non-whitespace character is found. Then it takes as many characters as possible to form a valid floating point representation and converts them to floating point value. The valid floating point value can be one of the following:
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    • espressione decimale in virgola mobile. Si compone delle seguenti parti:
      Original:
      decimal floating point expression. It consists of the following parts:
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    • (opzionale) più o segno meno
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      (opzionale) plus or minus sign
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    • sequenza non vuota di cifre decimali eventualmente contenenti un carattere punto decimale (definisce significante)
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      nonempty sequence of decimal digits optionally containing a decimal point character (defines significand)
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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)
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      (opzionale) e or E followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent)
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    • binario espressione virgola mobile. Si compone delle seguenti parti:
      Original:
      binary floating point expression. It consists of the following parts:
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    • (opzionale) più o segno meno
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      (opzionale) plus or minus sign
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    • 0x or 0X
    • sequenza non vuota di cifre esadecimali eventualmente contenenti un carattere punto decimale (definisce significante)
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      nonempty sequence of hexadecimal digits optionally containing a decimal point character (defines significand)
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    • (opzionale) p o P seguito con meno opzionali o segno più e la sequenza non vuota di cifre esadecimali (definisce esponente)
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      (opzionale) p or P followed with optional minus or plus sign and nonempty sequence of hexadecimal digits (defines exponent)
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    • infinito espressione. Si compone delle seguenti parti:
      Original:
      infinity expression. It consists of the following parts:
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    • (opzionale) più o segno meno
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      (opzionale) plus or minus sign
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    • INF o INFINITY ignorando caso
      Original:
      INF or INFINITY ignoring case
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    • not-a-numero di espressione. Si compone delle seguenti parti:
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      not-a-number expression. It consists of the following parts:
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    • (opzionale) più o segno meno
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      (opzionale) plus or minus sign
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    • NAN o NAN( char_sequence ) ignorando caso della parte NAN. Char_sequence' può contenere solo caratteri alfanumerici. Il risultato è un tranquillo punto di valore NaN mobile.
      Original:
      NAN or NAN(char_sequence) ignoring case of the NAN part. char_sequence can only contain alphanumeric characters. The result is a quiet NaN floating point value.
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    Parametri

    str -
    puntatore alla stringa con terminazione null byte da interpretare
    Original:
    pointer to the null-terminated byte string to be interpreted
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    Valore di ritorno

    double valore corrispondente al contenuto di str sul successo. Se il valore convertito cade nell'intervallo del tipo di ritorno, il valore restituito non è definito. Se la conversione non può essere eseguita, viene restituito 0.0.
    Original:
    double value corresponding to the contents of str on success. If the converted value falls out of range of the return type, the return value is undefined. If no conversion can be performed, 0.0 is returned.
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    Esempio

    This section is incomplete
    Reason: no example

    Vedi anche
    converte una stringa di byte in un valore in virgola mobile
    Original:
    converts a byte string to a floating point value
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    (funzione) [modifica]
    C documentation for atof