function
<ios> <iostream> <iostream>
std::boolalpha
ios_base& boolalpha (ios_base& str);
Alphanumerical bool values
Sets the boolalpha format flag for the str stream.
When the boolalpha format flag is set, bool values are inserted/extracted by their textual representation: either true or false, instead of integral values.
This flag can be unset with the noboolalpha manipulator.
For standard streams, the boolalpha flag is not set on initialization.
Parameters
- str
- Stream object whose format flag is affected.
Because this function is a manipulator, it is designed to be used alone with no arguments in conjunction with the insertion (<<) and extraction (>>) operations on streams (see example below).
Return Value
Argument str.
Example
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// modify boolalpha flag
#include <iostream> // std::cout, std::boolalpha, std::noboolalpha
int main () {
bool b = true;
std::cout << std::boolalpha << b << '\n';
std::cout << std::noboolalpha << b << '\n';
return 0;
}
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Output:
Data races
Modifies str. Concurrent access to the same stream object may cause data races.
Exception safety
Basic guarantee: if an exception is thrown, str is in a valid state.