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Fixes #5746

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Updates FAQ section of documentation

[SVN r73705]
This commit is contained in:
Antony Polukhin
2011-08-12 17:04:31 +00:00
parent 9955dcce51
commit 4a4150d0be
1 changed files with 16 additions and 2 deletions
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18
doc/lexical_cast.qbk
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@ -118,17 +118,29 @@ Exception used to indicate runtime lexical_cast failure.
[section Frequently Asked Questions]
* [*Question:] Why does `lexical_cast<int8_t>("127")` throw `bad_lexical_cast`?
* [*Answer:] The type `int8_t` is a `typedef` to `char` or `signed char`. Lexical conversion to these types
is simply reading a byte from source but since the source has more than one byte, the exception is thrown.
* [*Answer:] The type `int8_t` is a `typedef` to `char` or `signed char`. Lexical conversion to these types is simply reading a byte from source but since the source has more than one byte, the exception is thrown.
Please use other integer types such as `int` or `short int`. If bounds checking is important, you can also
call __numericcast__:
`numeric_cast<int8_t>(lexical_cast<int>("127"));`
[pre
]
* [*Question:] Why does `lexical_cast<unsigned char>("127")` throw `bad_lexical_cast`?
* [*Answer:] Lexical conversion to any char type is simply reading a byte from source. But since the source has more than one byte, the exception is thrown.
Please use other integer types such as `int` or `short int`. If bounds checking is important, you can also
call __numericcast__:
`numeric_cast<int8_t>(lexical_cast<int>("127"));`
[pre
]
* [*Question:] What does `lexical_cast<std::string>` of an `int8_t` or `uint8_t` not do what I expect?
* [*Answer:] As above, note that int8_t and uint8_t are actually chars and are formatted as such. To avoid
this, cast to an integer type first: `lexical_cast<std::string>(static_cast<int>(n));`
[pre
]
* [*Question:] The implementation always resets the `ios_base::skipws` flag of an underlying stream object.
It breaks my `operator>>` that works only in presence of this flag. Can you remove code that resets the flag?
@ -138,6 +150,8 @@ remember that __proposalshort__ is not yet accepted by the committee. By the way
make your `operator>>` conform to the standard.
Read a good C++ book, study `std::sentry` and [@boost:libs/io/doc/ios_state.html `ios_state_saver`].
[pre
]
* [*Question:] Why `std::cout << boost::lexical_cast<unsigned int>("-1");` does not throw, but outputs 4294967295?
* [*Answer:] `boost::lexical_cast` has the behavior of `std::stringstream`, which uses `num_get` functions of