std::strtof, std::strtod, std::strtold – cppreference.com

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definiert in Header `<cstdlib>`

`float strtof( const char* str, char** str_end );`		(seit C++11)

`double strtod( const char* str, char** str_end );`

`long double strtold( const char* str, char** str_end );`		(seit C++11)

Legt einen Gleitkommawert in einem Byte String, auf den str .

Original:

Interprets a floating point value in a byte string pointed to by str.

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Funktion verwirft alle Whitespace-Zeichen (wie std::isspace() bestimmt) bis zum ersten Nicht-Whitespace-Zeichen gefunden wird. Dann dauert es so viele Zeichen wie möglich, um eine gültige Gleitkomma-Darstellung bilden und wandelt sie in Fließkommazahl. Der gültige Gleitkommawert kann eine der folgenden sein:

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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Gleitpunktberechnungen Ausdruck. Es besteht aus folgenden Teilen:
Original:
decimal floating point expression. It consists of the following parts:
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(optional) Plus-oder Minuszeichen
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(optional) plus or minus sign
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nichtleere Folge von Dezimalziffern gegebenenfalls ein Dezimalzeichen (definiert Mantisse)
Original:
nonempty sequence of decimal digits optionally containing a decimal point character (defines significand)
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(optional) e oder E folgte mit optional Minus-oder Pluszeichen und nichtleere Folge von Dezimalziffern (definiert Exponent)
Original:
(optional) e or E followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent)
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binäre Fließkomma-Ausdruck. Es besteht aus folgenden Teilen:
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binary floating point expression. It consists of the following parts:
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(optional) Plus-oder Minuszeichen
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(optional) plus or minus sign
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0x or 0X
nichtleere Folge von Hexadezimalziffern gegebenenfalls ein Dezimalzeichen (definiert Mantisse)
Original:
nonempty sequence of hexadecimal digits optionally containing a decimal point character (defines significand)
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(optional) p oder P folgte mit optional Minus-oder Pluszeichen und nichtleere Folge von Hexadezimalziffern (definiert Exponent)
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(optional) p or P followed with optional minus or plus sign and nonempty sequence of hexadecimal digits (defines exponent)
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infinity Ausdruck. Es besteht aus folgenden Teilen:
Original:
infinity expression. It consists of the following parts:
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(optional) Plus-oder Minuszeichen
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(optional) plus or minus sign
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INF oder INFINITY ignorieren Fall
Original:
INF or INFINITY ignoring case
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not-a-number Ausdruck. Es besteht aus folgenden Teilen:
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not-a-number expression. It consists of the following parts:
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(optional) Plus-oder Minuszeichen
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(optional) plus or minus sign
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NAN oder NAN( char_sequence ) ignorieren Fall des NAN Teil. Char_sequence kann nur alphanumerische Zeichen enthalten. Das Ergebnis ist ein ruhiger NaN Gleitkommawert .
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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Die Funktionen setzt den Zeiger auf die durch str_end auf das Zeichen nach dem letzten Zeichen interpretiert zeigen. Wenn str_end NULL ist, wird es ignoriert .

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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Parameter

str	-	Zeiger auf die null-terminierte Byte-String interpretiert werden Original: pointer to the null-terminated byte string to be interpreted The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
str_end	-	Zeiger auf einen Zeiger auf ein Zeichen . Original: pointer to a pointer to character. The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Rückgabewert

Floating-Point-Wert, der den Inhalt der str auf Erfolg. Wenn der umgewandelte Wert fällt außerhalb der Reichweite des zugehörigen Rückgabetyp tritt Entfernungsfehlers und HUGE_VAL, HUGE_VALF oder HUGE_VALL zurückgegeben. Wenn keine Umwandlung durchgeführt werden kann, wird zurückgegeben 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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Beispiel

Siehe auch


	wandelt ein Byte String in eine Gleitkommazahl Original: converts a byte string to a floating point value The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Funktion) [edit]