original_string: public function add_prefix($field) {
          if (substr($field, 0, 2) === '!_') {
              return '-_' . $this->extraprefix . substr($field, 2);
          } else if (substr($field, 0, 1) === '-') {
              return '-' . $this->extraprefix . substr($field, 1);
          } else if (substr($field, 0, 1) === '_') {
              return '_' . $this->extraprefix . substr($field, 1);
          } else {
              return $this->extraprefix . $field;
          }
      }
code: public function add_prefix($field) {
          if (substr($field, 0, 2) === '!_') {
              return '-_' . $this->extraprefix . substr($field, 2);
          } else if (substr($field, 0, 1) === '-') {
              return '-' . $this->extraprefix . substr($field, 1);
          } else if (substr($field, 0, 1) === '_') {
              return '_' . $this->extraprefix . substr($field, 1);
          } else {
              return $this->extraprefix . $field;
          }
      }
code_tokens: public function add_prefix ( $ field ) { if ( substr ( $ field , 0 , 2 ) === '!_' ) { return '-_' . $ this -> extraprefix . substr ( $ field , 2 ) ; } else if ( substr ( $ field , 0 , 1 ) === '-' ) { return '-' . $ this -> extraprefix . substr ( $ field , 1 ) ; } else if ( substr ( $ field , 0 , 1 ) === '_' ) { return '_' . $ this -> extraprefix . substr ( $ field , 1 ) ; } else { return $ this -> extraprefix . $ field ; } }
docstring: Add the extra prefix to a field name.
  @param string $field the plain field name.
  @return string the field name with the extra bit of prefix added.
docstring_tokens: Add the extra prefix to a field name .