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#include <seqan3/alphabet/alphabet_base.hpp>
#include <seqan3/alphabet/concept.hpp>
#include <seqan3/utility/char_operations/transform.hpp> // seqan3::to_lower
class ab : public seqan3::alphabet_base<ab, 2>
{
private:
// make the base class a friend so it can access the tables:
friend alphabet_base<ab, 2>;
// This function is expected by seqan3::alphabet_base
static constexpr char_type rank_to_char(rank_type const rank)
{
// via a lookup table
return rank_to_char_table[rank];
// or via an arithmetic expression
return rank == 1 ? 'B' : 'A';
}
// This function is expected by seqan3::alphabet_base
static constexpr rank_type char_to_rank(char_type const chr)
{
// via a lookup table
using index_t = std::make_unsigned_t<char_type>;
return char_to_rank_table[static_cast<index_t>(chr)];
// or via an arithmetic expression
return seqan3::to_lower(chr) == 'b' ? 1 : 0;
}
private:
// === lookup-table implementation detail ===
// map 0 -> A and 1 -> B
static constexpr std::array<char_type, alphabet_size> rank_to_char_table{'A', 'B'};
// map every letter to rank zero, except Bs
static constexpr std::array<rank_type, 256> char_to_rank_table{
// initialise with an immediately evaluated lambda expression:
[]()
{
std::array<rank_type, 256> ret{}; // initialise all values with 0 / 'A'
// only 'b' and 'B' result in rank 1
ret['b'] = 1;
ret['B'] = 1;
return ret;
}()};
};
// The class ab satisfies the alphabet concept.
static_assert(seqan3::alphabet<ab>);
static_assert(seqan3::writable_alphabet<ab>);
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