4.10 sdds::Page row and field transformations

• name:
  Page::matchRows, Page::filtered, Page::projected, Page::matrix
• description:
  Create immutable filtered or projected page copies and extract selected numeric columns as a contiguous row-major matrix. matchRows produces a mask by testing each value in a loaded column.
• synopsis:
  sdds::RowMask Page::matchRows(  
      std::string_view column,  
      const std::function<bool(const sdds::Scalar &)> &predicate) const;  
  template<class T, class Predicate>  
  sdds::RowMask Page::matchRows(std::string_view column,  
                                Predicate predicate) const;  
  sdds::Page Page::filtered(const sdds::RowMask &mask) const;  
  sdds::Page Page::projected(const sdds::ReadRequest &request) const;  
  template<class T>  
  sdds::DenseMatrix<T> Page::matrix(  
      const std::vector<std::string> &columns,  
      sdds::ConversionMode conversion = sdds::ConversionMode::Exact,  
      sdds::RoundingMode rounding = sdds::RoundingMode::Reject) const;

• arguments:
  • column, columns — Source column name or ordered names.
  • predicate — Callable used to select rows.
  • mask — Mask having one entry per page row.
  • request — Field and row projection.
  • conversion — Require exact types or use checked conversion.
  • rounding — Rounding policy used by checked conversion.
• return value:
  A mask, transformed page, or DenseMatrix<T>. A dense matrix exposes rows, columns, a row-major values vector, and checked operator()(row,column) access.
• exceptions:
  sdds::StateError, sdds::TypeError, or sdds::LimitError for unavailable data, incompatible types, or excessive transformation output.
• see also:
  Sections 4.6, 4.9, and 4.21.