piromanas

switch (state) {                                case state::binary :                                         if ( i != input.end() && (*i)->type == state::value ) {                                            i1 = i ;                                            ++i ;                                            if ( i != input.end() && (*i)->type == state::operation ) {                                                o = i ;                                                ++i ;                                                if ( i != input.end() && (*i)->type == state::value ) {                                                    *o->left = *i1 ;                                                    *o->right = *i ;                                                    input.erase(i1) ;                                                    input.erase(i) ;                                                    i = input.begin() ;                                                    state = state::binary ;                                                }                                            }                                        }                                        else if ( i != input.end() ) {                                            state = state::binary ;                                            ++i ;                                        }                                        else if ( i == input.end() ) {                                            state = state::unary ;                                        }                                                                                break ;            }