Namespace
Varianti

std::strtof, std::strtod, std::strtold

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< cpp‎ | string‎ | byte

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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
 
Null-stringhe terminate byte
Funzioni
Original:
Functions
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Carattere manipolazione
Original:
Character manipulation
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Le conversioni in formati numerici
Original:
Conversions to numeric formats
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strtoul
strtoull
strtof
strtod
strtold
Della gestione delle stringhe
Original:
String manipulation
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strcpy
strncpy
strcat
strncat
strxfrm
String esame
Original:
String examination
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Memoria manipolazione
Original:
Memory manipulation
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memchr
memcmp
memset
memcpy
memmove
Varie
Original:
Miscellaneous
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strerror
 
Elemento definito nell'header <cstdlib>
float       strtof( const char* str, char** str_end );
 (dal C++11)
double      strtod( const char* str, char** str_end );
long double strtold( const char* str, char** str_end );
 (dal C++11)
Interpreta un valore in virgola mobile in una stringa di byte puntato da str.
Original:
Interprets a 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
    Original:
    (opzionale) plus or minus sign
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  • sequenza non vuota di cifre decimali eventualmente contenenti un carattere punto decimale (definisce significante)
    Original:
    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)
    Original:
    (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
    Original:
    (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)
    Original:
    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
    Original:
    (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:
    Original:
    not-a-number expression. It consists of the following parts:
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  • (opzionale) più o segno meno
    Original:
    (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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Le funzioni imposta il puntatore puntato da str_end per puntare al carattere dopo l'ultimo carattere interpretato. Se str_end è NULL, viene ignorato.
Original:
The functions sets the pointer pointed to by str_end to point to the character past the last character interpreted. If str_end is NULL, it is ignored.
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Indice

[modifica] 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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str_end -
puntatore a un puntatore a carattere .
Original:
pointer to a pointer to character.
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[modifica] Valore di ritorno

Valore in virgola mobile che corrisponde al contenuto di str in caso di successo. Se il valore convertito cade fuori dalla portata del corrispondente tipo di ritorno, errore di campo si verifica e HUGE_VAL, HUGE_VALF o HUGE_VALL viene restituito. Se la conversione non può essere eseguita, viene restituito ​0​.
Original:
Floating point value corresponding to the contents of str on success. If the converted value falls out of range of corresponding return type, range error occurs and HUGE_VAL, HUGE_VALF or HUGE_VALL is returned. If no conversion can be performed, ​0​ is returned.
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[modifica] Esempio

This section is incomplete
Reason: no example

[modifica] 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 strtof, strtod, strtold
Estratto da "https://it.cppreference.com/mwiki/index.php?title=cpp/string/byte/strtof&oldid=26769"