code: public int getFieldExprIndex(final String _expr)
      {
          int ret = -1;
          if (getAllFieldExpr().containsKey(_expr)) {
              final Integer ident = getAllFieldExpr().get(_expr);
              ret = ident.intValue();
          }
          return ret;
      }
docs: For the parameter <i>_expr</i> the index in the list of all field
  expressions is returned.
  
  @param _expr expression for which the index is searched
  @return index of the field expression
  @see #addFieldExpr
  @see #getAllFieldExpr
  @see #allFieldExpr