tmp/tmpifjjhw5c/{from.md → to.md}
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| 1 |
+
### Primitive numeric output conversion <a id="charconv.to.chars">[[charconv.to.chars]]</a>
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All functions named `to_chars` convert `value` into a character string
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by successively filling the range \[`first`, `last`), where \[`first`,
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`last`) is required to be a valid range. If the member `ec` of the
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return value is such that the value is equal to the value of a
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value-initialized `errc`, the conversion was successful and the member
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`ptr` is the one-past-the-end pointer of the characters written.
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Otherwise, the member `ec` has the value `errc::value_too_large`, the
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member `ptr` has the value `last`, and the contents of the range
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\[`first`, `last`) are unspecified.
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The functions that take a floating-point `value` but not a `precision`
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parameter ensure that the string representation consists of the smallest
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number of characters such that there is at least one digit before the
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radix point (if present) and parsing the representation using the
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corresponding `from_chars` function recovers `value` exactly.
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[*Note 1*: This guarantee applies only if `to_chars` and `from_chars`
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are executed on the same implementation. — *end note*]
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If there are several such representations, the representation with the
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smallest difference from the floating-point argument value is chosen,
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resolving any remaining ties using rounding according to
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`round_to_nearest` [[round.style]].
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The functions taking a `chars_format` parameter determine the conversion
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specifier for `printf` as follows: The conversion specifier is `f` if
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`fmt` is `chars_format::fixed`, `e` if `fmt` is
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`chars_format::scientific`, `a` (without leading `"0x"` in the result)
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if `fmt` is `chars_format::hex`, and `g` if `fmt` is
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`chars_format::general`.
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``` cpp
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to_chars_result to_chars(char* first, char* last, see below value, int base = 10);
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```
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*Preconditions:* `base` has a value between 2 and 36 (inclusive).
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*Effects:* The value of `value` is converted to a string of digits in
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the given base (with no redundant leading zeroes). Digits in the range
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10..35 (inclusive) are represented as lowercase characters `a`..`z`. If
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`value` is less than zero, the representation starts with `’-’`.
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*Throws:* Nothing.
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*Remarks:* The implementation shall provide overloads for all signed and
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unsigned integer types and `char` as the type of the parameter `value`.
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``` cpp
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to_chars_result to_chars(char* first, char* last, float value);
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to_chars_result to_chars(char* first, char* last, double value);
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to_chars_result to_chars(char* first, char* last, long double value);
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```
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*Effects:* `value` is converted to a string in the style of `printf` in
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the `"C"` locale. The conversion specifier is `f` or `e`, chosen
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according to the requirement for a shortest representation (see above);
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a tie is resolved in favor of `f`.
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*Throws:* Nothing.
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``` cpp
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to_chars_result to_chars(char* first, char* last, float value, chars_format fmt);
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to_chars_result to_chars(char* first, char* last, double value, chars_format fmt);
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to_chars_result to_chars(char* first, char* last, long double value, chars_format fmt);
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```
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*Preconditions:* `fmt` has the value of one of the enumerators of
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`chars_format`.
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*Effects:* `value` is converted to a string in the style of `printf` in
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the `"C"` locale.
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*Throws:* Nothing.
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``` cpp
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to_chars_result to_chars(char* first, char* last, float value,
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chars_format fmt, int precision);
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to_chars_result to_chars(char* first, char* last, double value,
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chars_format fmt, int precision);
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to_chars_result to_chars(char* first, char* last, long double value,
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chars_format fmt, int precision);
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```
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*Preconditions:* `fmt` has the value of one of the enumerators of
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`chars_format`.
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*Effects:* `value` is converted to a string in the style of `printf` in
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the `"C"` locale with the given precision.
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*Throws:* Nothing.
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See also: ISO C 7.21.6.1
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