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Constructor.
template< class Pred> constexpr lut_chars( Pred const& pred);
This function constructs a character set which has as members, every
value of char ch
for which the expression pred(ch)
returns true
.
struct is_digit { constexpr bool operator()(char c ) const noexcept { return c >= '0' && c <= '9'; } }; constexpr lut_chars digits( is_digit{} );
Linear in pred
, or constant
if pred(ch)
is a constant expression.
Throws nothing.
Name |
Description |
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The function object to use for determining membership in the character set. |