grammar::lut_chars::lut_chars (3 of 3 overloads)

Constructor.

Synopsis

template<
    class Pred>
constexpr
lut_chars(
    Pred const& pred);

Description

This function constructs a character set which has as members, every value of char ch for which the expression pred(ch) returns true.

Example

struct is_digit
{
    constexpr bool
    operator()( char c ) const noexcept
    {
        return c >= '0' && c <= '9' ;
    }
};

constexpr lut_chars digits( is_digit{} );

Complexity

Linear in pred, or constant if pred(ch) is a constant expression.

Exception Safety

Throws nothing.

Parameters

Name	Description
`pred`	The function object to use for determining membership in the character set.