value::to_number

Return the stored number cast to an arithmetic type.

Synopsis

template<
    class T>
T
to_number(
    boost::system::error_code& ec) const noexcept; (1)

template<
    class T>
T
to_number(
    std::error_code& ec) const noexcept; (2)

template<
    class T>
T
to_number() const; (3)

Description

This function attempts to return the stored value converted to the arithmetic type T which may not be bool:

  • If T is an integral type and the stored value is a number which can be losslessly converted, the conversion is performed without error and the converted number is returned.

  • If T is an integral type and the stored value is a number which cannot be losslessly converted, then the operation fails with an error.

  • If T is a floating point type and the stored value is a number, the conversion is performed without error. The converted number is returned, with a possible loss of precision.

  • Otherwise, if the stored value is not a number; that is, if is_number() returns false, then the operation fails with an error.

Constraints

std::is_arithmetic< T >::value && ! std::is_same< T, bool >::value

Complexity

Constant.

Exception Safety

  • (1), (2) no-throw guarantee.

  • (3) strong guarantee.

Return Value

The converted number.

Parameters

Name Description

ec

Set to the error, if any occurred.

Exceptions

Type Thrown On

boost::system::system_error

Overload (3) reports errors by throwing an exception.
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