Function to_lower

test-app/runtime/src/main/cpp/ada/ada.h:1034–1034

constexpr bool is_digit(char x) noexcept { return (x >= '0') & (x <= '9'); }

constexpr char to_lower(char x) noexcept { return (x | 0x20); }

constexpr bool is_alpha(char x) noexcept {
  return (to_lower(x) >= 'a') && (to_lower(x) <= 'z');