void a()
{
  Serial.println( "a" );
}


void b()
{
  Serial.println( "b" );
}


void exec( char const * const input )
{
  struct function_t
  {
    char const * const name;
    void const (* const pointer)();
  };
  
  static const function_t functions[] =
  {
    { "a", a },
    { "b", b },
  };

  bool error = true;

  for ( const function_t function : functions )
  {
    if ( !strcmp( input, function.name ) )
    {
      function.pointer();
      error = false;
      break;
    }
  }

  if ( error == true )
  {
    Serial.println( "error" );
  }
}


void setup()
{
  Serial.begin( 115200 );

  exec( "a" );
  exec( "b" );
  exec( "c" );
}


void loop()
{
}