Präprozessor(?): Zeichen in Zeichenkette ersetzen

const char *leberkaes = "Leberk\x84s";

const char *knoedel = "Kn\x94del";

extern void real_write_c (char);

static char map_uml (char c)

{

    switch (c)

    {

        default: break;

        case 'ä': c = '\x12'; break;

        case 'ö': c = '\x8f'; break;

        ...

    }

    return c;

}

void write_c (char c)

{

    real_write_c (map_ump (c));

}

#include <cstddef>

#include <array>

#include <cstdio>

template <typename T, T... I>

struct IntegerSequence {

  using value_type = T;

  static constexpr size_t size () { return sizeof... (I); }

};

namespace Helper {

  template <typename T, typename S1, typename S2>

  struct ConcatSequence;

  template <typename T, T... S1, T... S2>

  struct ConcatSequence<T, IntegerSequence<T, S1...>, IntegerSequence<T, S2...>> {

    using type = IntegerSequence<T, S1..., (sizeof...(S1) + S2)...>;

  };

  template <typename T, T N, bool isZero, bool isOne>

  struct GenSeqI;

}

template <typename T, T N>

using GenSeq = typename Helper::GenSeqI<T, N, N == 0, N == 1>::type;

namespace Helper {

  template <typename T, T N>

  struct GenSeqI<T, N, false, false> {

    using type = typename ConcatSequence<T, GenSeq<T, N/2>, GenSeq<T, N-N/2>>::type;

  };

  template <typename T, T N>

  struct GenSeqI<T, N, true, false> {

    using type = IntegerSequence<T>;

  };

  template <typename T, T N>

  struct GenSeqI<T, N, false, true> {

    using type = IntegerSequence<T, 0>;

  };

}

inline constexpr char replace (char value) {

  return

    value == 'ö' ? 'o' :

    value == 'ä' ? 'a' :

    value == 'ü' ? 'u' :

    value;

}

template <size_t N, size_t... I>

inline constexpr const std::array<char, N> replace (const char (&str) [N], IntegerSequence<size_t, I...>*) {

  return {{ replace (str [I])... }};

}

template <size_t N>

inline constexpr const std::array<char, N> replace (const char (&str) [N]) {

  return replace<N> (str, static_cast<GenSeq<size_t, N>*> (nullptr));

}

/// ----------

constexpr auto myString1 = replace ("Hällö Leüte");

int main () {

  puts (myString1.data ());

}

puts (LCD_REPLACE_STR("Hällö Leüte"));