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NAME

       sps - standard spreadsheet module

STANDARD SPREADSHEET MODULE

       The  Standard Spreadsheet module is an original implementation that provides the necessary
       objects for designing a spreadsheet. A spreasheet acts a great interface  which  structure
       data  in  the  form  of  record  and  sheets.  Once structured, these data can be indexed,
       manipulated and exported into various formats.

       Spreadsheet concepts
       The sole purpose of using a spreadsheet is to collect various data and store them in  such
       a  way  that  they can be accessed later. Unlike standard spreadsheet system, the standard
       spreadsheet module does not place restrictions on the data organization.  The  spreadsheet
       module  stores  data in a hierarchical fashion. The basic data element is called a cell. A
       set of cells is a record. A set of records is a sheet. A set of sheets and  records  is  a
       folio.

       Cell and data
       A cell is a data container. There is only one data element per cell. Eventually a name can
       be associated with a cell. The cell data can be any kind of literals.  Such  literals  are
       integer, real, boolean, character or strings.

       Record
       A  record is a vector of cells. A record can be created by adding cell or simply by adding
       data. If the record has a predefined size, the cell or data can be set by indexing.

       Sheet
       A sheet is a vector of records. A sheet can be created by adding record. Similarly, if the
       sheet  has  a  predefined  size, record cell or data can be added by indexing. A sheet can
       also be seen as a 2 dimensional  array  of  cells.  For  the  purpose  of  managing  extra
       information,  the  sheet  carry also several extra records, namely, the marker record, the
       header record and footer record as well as the tag vector and the signature.

       Folio
       A folio is a set of sheets and/or records. A folio of sheets permits to structure data  in
       the form of tables. Since cell, record and table can have a name, it is possible to create
       link between various elements, thus creating a collection of structured data.

       Storage model
       There are several ways to integrate data. In the simplest form, data are integrated  in  a
       record  list.  A  complex model can be built with a sheet. More complex models can also be
       designed by using a folio.

       Single record model
       With a single record model, the data are accumulated in a single array. This kind of  data
       storing  is  particularly adapted for single list recording. As a single record, the basic
       search and sorting algorithm can be applied. For instance, a list name can be stored as  a
       single  record.  With  this  view,  there  is no difference between a list, a vector and a
       record. The record can also be named.

       Record importation
       Data are imported into the record, either by  construction,  list  or  stream.  Since  the
       record  object  is  a  serializeable  object,  the  importation  process is also performed
       automatically in the collection. The base record importation  class  implements  a  simple
       importation  model  based  on  blank separated literals. Complex importation models can be
       devised by derivation. A special case with a cons cell is also supported where the car  is
       the cell name and the cadr is the cell object.

       # an example of file importation
       1   "a string" 'a'

       The  previous  example  shows the file structure that can be used to import cell data. The
       fist line defines a record with 3 cells. The second line defines  also  a  record  with  3
       cells. The second cell is a named cell.

       Record exportation
       A  record  is  an  object  that  can  be  serialized. It can therefore be exported easily.
       However, in the serialized form, the record is in a binary form. It is  also  possible  to
       walk through the record and exports, for each cell its literal form.

       Folio indexation
       There  are  various ways to access a folio by reference. Since a folio can contain several
       sheets, it seems natural to access them by tag. The other method is to index the cells  in
       a cross-reference album in order to access rapidly.

       Sheet access model
       The  sheet  access model uses a tag to access one or several sheets in a folio. A tag is a
       string attached to a sheet. It is possible in a folio to have several sheet with the  same
       tag.  It  is  also possible to attach several tags to a sheet. When a folio is searched by
       tag, the first sheet that matches the tag is said to be the valid one. If all sheets  that
       match  the  requested  tag  are  needed, it is possible to create a derived folio with all
       sheets that match the requested tag.

       Cell access model
       The cell access model operates with a cross-reference table built with an index. An  index
       is  a multiple entry record that stores the cell location. A cell coordinate comprises the
       cell index in the record, the record index in the sheet and the sheet index in the  folio.
       If  an  index  contains multiple entries, this indicates that several cells are indexed. A
       cell cross-reference table is a collection of index. Generally the index name is the  cell
       name.  When the cross-reference table is built, all cell of interests are scanned and if a
       cell name exists, the cell is indexed in the cross-reference table. If there  are  several
       cells with the same name, the index length associated with the name is the number of cells
       with that name.

       Search and access
       The methodology for searching is to decide whether a sheet or a cell should be accessible.
       If  a  sheet access is desired, the search by tag method is the preferred way. This method
       assumes that the requested sheet is structured in a particular way, known to the user.  If
       a  cell  access seems more appropriate, a cross-reference table should be built first, and
       the search done from it. In the case of search by tag, the method is dynamic and  operates
       well  when  sheets are added in a folio. When a cross-reference table is used, proper care
       should be taken to rebuild the cross-reference table when some sheets are added unless the
       user knows that there is no need for it.

       Folio object
       The  Folio  object  is  the  primary  object used for storing data. Although, a folio is a
       collection of sheets, it the primary object that should be created when manipulating  such
       collection.

       Creating a folio
       The  Folio object is built without argument. In this case, the folio is empty. A predicate
       is available for testing the Folio object.

       const sps (afnix:sps:Folio)
       afnix:sps:folio-p sps # true

       The constructor can operate also by name or by input stream. With a string,  a  new  folio
       those  name  is the argument is created. By stream, a new folio is created and loaded with
       the input stream data. Eventually, the folio name can be set with the set-name command and
       retrieved with the get-name command.

       const sps (afnix:sps:Folio)
       sps:set-name "planets"

       Sheet object
       The Sheet object is the primary object used to store data in a folio. Since a Folio object
       is a collection of sheets, a sheet can be manipulated either by getting  getting  it  from
       the folio or by creating it independently and adding it into the folio.

       Creating a sheet
       An  empty  sheet  can be created simply with or without name. Without argument, an unnamed
       sheet is created. Similar to the Folio class, the sheet name can be passed at construction
       or set with the set-name method. As usual a predicate is provided.

       const sht (afnix:sps:Sheet)
       afnix:sps:sheet-p sht # true

       When the sheet is created, it can be added to the folio spreadsheet with the add method.

       const sht (afnix:sps:Sheet "data")
       sps:add sht

       Adding data to the sheet
       The  process  of  adding  data to a sheet is a straightforward operation with the add-data
       method or the add method. With the add-data method, data are added as literals.  With  the
       add method, data are added with the help of a record object.

       sht:add-data "Mercury"   4840 "1407:36"
       sht:add-data "Venus"    12400 "5819:51"
       sht:add-data "Earth"    12756 "23:56"
       sht:add-data "Mars"      6800 "24:37"
       sht:add-data "Jupiter" 142800 "9:50"
       sht:add-data "Saturn"  120800 "10:14"
       sht:add-data "Uranus"   47600 "10:49"
       sht:add-data "Neptune"  44600 "15:40"
       sht:add-data "Pluto"     5850 "153:17"
       sht:add-data "Sedna"     1800 "960:00"

       Data  can  be  imported  in  a  sheet  by  importation  with  an  input stream. During the
       importation, the serialized data are decoded and placed sequentially in the stream.

       Sheet sorting
       A sheet can be sorted with the sort  method.  The  sort  method  uses  the  first  integer
       argument  as  the  column  number. The second optional argument is a boolean argument that
       selects the sorting method which can be ascending (by default) or descending if  the  flag
       is false.

       sht:sort 0
       sht:sort 1 false

       Record object
       The  Record  object  is an alternative to the sheet data filling. With the help of the add
       method, a record can be added to a sheet.

       Creating a record
       A record is a named object that acts as a vector of cells. The  record  name  can  be  set
       either by construction or with the set-name method. As usual a predicate is provided.

       const rcd (afnix:sps:Record)
       afnix:sps:record-p # true

       Filling a record
       A  record  can  be filled either with literal data or Cell objects. In the first case, the
       cell is automatically created for each literal added to the record. The add method  add  a
       cell or literal to the record.

       const rcd (Record)
       rcd:add "Mercury" 4840 "1407:36"

       For data extraction, the length method returns the record length. Data can be extracted by
       index with either the get or map method. The get method returns the record cell while  the
       map method returns the cell literal.

       Object search
       The search methodology is divided either by sheet or cells. In a folio, the search is done
       in terms of sheets while the construction of  a  cross-reference  table  is  required  for
       searching cells.

       Searching in a folio
       The  Folio  object  provides  the  primary  mean  to search for sheet. The find and lookup
       methods return a sheet by tag. The first sheet that matches the tag is returned  by  these
       methods.  The find method returns nil if the sheet cannot be found while the lookup method
       throws an exception.

       # get a sheet by tag
       const sheet (folio:lookup "the tag")

       If there are several sheets that matched the tag, the filter method is  more  appropriate.
       The  filter  method returns a new folio that contains the sheet that matches the requested
       tag.

       # get a sub-folio by tag
       const sf (folio:filter "the tag")

       Searching for a cell
       The Folio object also provides the method for building a cross-reference table. The cross-
       reference  table  is  represented  by  the Xref object. By default, a complete Xref object
       table is built with the getxref folio method. Such method, scan all cells in the folio and
       add them in the cross-reference table if the cell has a name.

       # get a default xref table
       const xref (folio:getxref)

       The  cross-reference  table  can  also be built by searching for sheet tags. With a string
       argument, the getxref search for all sheets that matches the tag and then build  a  cross-
       reference table. This method is equivalent to the operation of building a new folio by tag
       with the filter method and then building the cross-reference table.

       # get a xref table by tag
       const xref (folio:getxref "the tag")
       # another method
       const sf   (folio:filter "the tag")
       const xref (sf:getxref)

       A cross-reference table can also be built by cell index and/or record index. With  a  cell
       index, the cross-reference table is built by indexing the sheet column. With both the cell
       and record indexes, the cross-reference table is  built  by  indexing  all  cells  at  the
       coordinate for all sheets.

       # get a xref table by cell index
       const xref (folio:getxref 0)
       # get a xref table by cell and record index
       const xref (folio:getxref 0 1)

STANDARD SPREADSHEET REFERENCE

       Cell
       The  Cell class is a data container. There is only one data element per cell. Eventually a
       name can be associated with a cell. The cell data  can  be  any  kind  of  literals.  Such
       literals  are integer, real, boolean, character or strings. A cell is the basic block used
       to build a spreadsheet.

       Predicate

              cell-p

       Inheritance

              Nameable

       Constructors

              Cell (none)
              The Cell constructor create a  default  cell  with  no  name  and  no  value.  When
              evaluated, the cell returns nil.

              Cell (Literal)
              The  Cell  constructor  create  a  default cell by value. The argument is a literal
              object which can be viewed with its string representation.

              Cell (String Literal)
              The Cell constructor create a default cell by name and value. The first argument is
              the cell name. The second argument is a literal object which can be viewed with its
              string representation.

       Methods

              get -> Literal (none)
              The get method returns the cell literal value.

              set -> none (Literal)
              The set method sets the cell literal value.

              get-name -> String (none)
              The get-name method returns the cell name.

              set-name -> none (String)
              The set-name method sets the cell name.

       Persist
       The Persist class is a base class for the  AFNIX  spreadsheet module.  The  class  defines
       the  methods  that  are used to read of write a particular persistent object. When saving,
       the object name is retreived with the get name method. The saveas method does the same  as
       save but takes a file name argument.

       Predicate

              persist-p

       Inheritance

              Nameable

       Methods

              save -> none (none)
              The save method saves the current object.

              saveas -> none (String)
              The  saveas  method saves the current object into the file those name is the string
              argument.

       Record
       The Record class is a cell container. A record can be created by adding cell or simply  by
       adding data. If the record has a predefined size, the cell or data can be set by indexing.
       A name can be attached to the record. Facilities are provided to access directly the  cell
       associated with the record. A record can also be created by name.

       Predicate

              record-p

       Inheritance

              Persist

       Constructors

              Record (none)
              The Record constructor create an empty record with no name and no cell.

              Record (String)
              The  Record  constructor  create  an empty record by name name. The argument is the
              record name to use.

       Methods

              add -> none (Cell|Literal...)
              The add method adds one or several cell objects to the record. In the  first  form,
              the  argument  is  a  cell  that  is  added  in the record. In the second form, the
              argument is a literal that is used to create a cell by value.

              get -> Cell (Integer)
              The get method returns a record cell by index. The index must be within the  record
              range or an exception is raised.

              map -> Literal (Integer)
              The  map  method  map  a  record cell by index. The index must be within the record
              range or an exception is raised. The cell is mapped to a literal object.

              set -> none (Integer Cell|Literal)
              The set method sets the record cell by index. The record index  must  be  valid  in
              order  to succeed. A new cell is created prior the record update. The previous cell
              data is lost including its name.

              sort -> none (none|Boolean)
              The sort method sorts a record in place. Without argument, the record is sorted  in
              ascending order. The optional boolean argument specifies the sorting mode. If true,
              the record is sorting in ascending order and in descending order if false.

              find -> Cell (String)
              The find method finds a cell by name. If the cell is not found, the nil  object  is
              returned. This method is similar to the lookup method.

              get-index -> Integer (String)
              The  get-index  method  finds  a  cell  index by name. If the cell is not found, an
              exception is raised. The index is the cell position in the record.

              lookup -> Cell (String)
              The lookup method finds a cell by name. If the cell is not found, an  exception  is
              raised. This method is similar to the find method.

              length -> Integer (none)
              The length method returns the record length.

              get-name -> String (none)
              The get-name method returns the record name.

              reset -> none (none)
              The  reset  method  rest  the record. The record name is not changed but all record
              cells are removed.

              set-name -> none (String)
              The set-name method sets the record name.

       Sheet
       The Sheet class is a  record  container.  A  sheet  can  be  created  by  adding  records.
       Similarly,  if  the  sheet  has  a  predefined  size,  record cell or data can be added by
       indexing. A sheet can be also seen as a 2 dimensional array of cells.  Like  a  record,  a
       sheet  can be named. Without argument, a default sheet is created. With a string argument,
       the sheet is created with an initial name.

       Predicate

              sheet-p

       Inheritance

              Persist

       Constructors

              Sheet (none)
              The Sheet constructor create an empty sheet with no name and no cell.

              Sheet (String)
              The Sheet constructor create an empty sheet by name. The argument is the sheet name
              to use.

              Sheet (String String)
              The Sheet constructor create an empty sheet by name and info. The first argument is
              the sheet name to use. The second argument is the sheet information string.

       Methods

              add -> none (Record)
              The add method adds a record to the sheet.

              get -> Record (Integer)
              The get method returns a sheet record by index. The index must be within the  sheet
              range or an exception is raised.

              set -> none (Integer Record)
              The  set  method  sets  the sheet record by index. The sheet index must be valid in
              order to succeed.

              sort -> none (none|Integer|Boolean|Integer Boolean)
              The sort method sorts the sheet in place.  By  default,  the  sheet  is  sorted  in
              ascending  order  with  column 0. With one argument, the argument can be either the
              sorting mode or the column number. If the mode is true,  the  sheet  is  sorted  in
              ascending  mode. If the mode is false, the sheet is sorted in descending mode. With
              two arguments, the first argument is the  column  number  and  the  second  is  the
              sorting mode.

              length -> Integer (none)
              The length method returns the sheet length.

              convert -> PrintTable ([Integer [Integer [Boolean]]])
              The  convert  method  converts the sheet into a print-table representation. Without
              argument, the whole sheet is converted. With one argument, the sheet  is  converted
              unto  a  maximum  of  rows.  The  second  optional argument is the start index that
              default to 0. The third optional argument is the literal format.  By  default,  the
              literal  is formatted as a string. If the flag is true, the literal is formatted as
              a literal string representation.

              add-data -> none ([Cell|Literal]+)
              The add-data method adds one or several cell object to a sheet  record.  The  sheet
              record  is  initially created and the object elements are added sequentially to the
              record. In the first form, the argument is a cell that is added in the  record.  In
              the second form, the argument is a literal that is used to create a cell by value.

              add-marker -> none ([Literal]+)
              The add-marker method adds one or several literal objects to a sheet marker record.

              marker-length -> Integer (none)
              The marker-length method returns the number of markers defined for this sheet.

              get-marker -> Cell (Integer)
              The get-marker method returns a marker cell by index from the sheet marker record.

              set-marker -> none (Integer Literal)
              The set-marker method set the sheet marker record by index and literal.

              find-marker -> Integer (String)
              The  find-marker  method  find  the marker index. The argument is the marker string
              value.

              add-sign -> none ([Literal]+)
              The add-sign method adds one or several literal objects to a sheet sign record.

              signature-length -> Integer (none)
              The signature-length method returns the number of signs defined for this sheet.

              get-sign -> Cell (Integer)
              The get-sign method returns a sign cell by index from the sheet sign record.

              set-sign -> none (Integer Literal)
              The set-sign method set the sheet sign record by index and literal.

              find-sign -> Integer (String)
              The find-sign method find the sign index. The argument is the sign string value.

              add-header -> none (Cell|Literal...)
              The add-header method adds one or several cell object to a sheet header record.  In
              the  first  form, the argument is a cell that is added in the record. In the second
              form, the argument is a literal that is used to create a cell by value.

              get-header -> Cell (Integer)
              The get-header method returns a header cell by index from the sheet header record.

              map-header -> Literal (Integer)
              The map-header method maps to a literal object a header  cell  by  index  from  the
              sheet header record.

              set-header -> none (Integer Literal)
              The  set-header  method  set  the  header  record  by  index  and literal. The cell
              associated with the header record is updated with the literal value.

              add-footer -> none ([Cell|Literal]+)
              The add-footer method adds one or several cell object to a sheet footer record.  In
              the  first  form, the argument is a cell that is added in the record. In the second
              form, the argument is a literal that is used to create a cell by value.

              get-footer -> Cell (Integer)
              The get-footer method returns a footer cell by index from the sheet footer record.

              map-footer -> Literal (Integer)
              The map-footer method maps to a literal object an footer cell  by  index  from  the
              sheet footer record.

              set-footer -> none (Integer Literal)
              The  set-footer  method  set  the  footer  record  by  index  and literal. The cell
              associated with the footer record is updated with the literal value.

              get-name -> String (none)
              The get-name method returns the sheet name.

              set-name -> none (String)
              The set-name method sets the sheet name.

              get-info -> String (none)
              The get-info method returns the sheet info.

              set-info -> none (String)
              The set-info method sets the sheet info.

              add-tag -> none ([String]+)
              The add-tag method adds a tag into the tags vector. The tag can be used to  mark  a
              sheet in a folio.

              tag-p -> Boolean (string)
              The tag-p method returns true if the given tag is defined for this sheet.

              tag-length -> Integer (none)
              The tag-length method returns the number of tags defined for this sheet.

              get-tag -> String (Integer)
              The get-tag method returns a tag by index.

              set-tag -> none (Integer Literal)
              The set-tag method set the sheet tag record by index and literal.

              find-tag -> Integer (String)
              The find-tag method find the tag index. The argument is the tag string value.

              reset -> none (none)
              The  reset  method  resets  the sheet. The name and information is unchanged during
              this operation.

       Folio
       The Folio class is a sheet container. A folio  of  sheets  can  be  structured  to  handle
       various  data  organization. Since all objects are named, it is possible to index them for
       fast data search. An empty folio can be created by name or filled with an input stream.

       Predicate

              folio-p

       Inheritance

              Persist

       Constructors

              Folio (none)
              The Folio constructor create an empty folio with no name and no cell.

              Folio (String)
              The Folio constructor create an empty folio by name. The argument is the folio name
              to use.

              Folio (String String)
              The Folio constructor create an empty folio by name and info. The first argument is
              the folio name to use. The second argument is the folio information string.

              Folio (InputStream)
              The Folio constructor create an empty folio and fill it by reading  the  data  from
              the input stream. The input stream must have the data in a serialized form.

       Methods

              write -> none (OutputStream)
              The  write method write the folio contents to an output stream. The written form is
              a serialized form.

              add -> none (Sheet)
              The add method adds a sheet to the folio.

              get -> Sheet (Integer)
              The get method returns a sheet by index. The index must be within the  folio  range
              or an exception is raised.

              set -> none (Integer Sheet)
              The  set  method  sets  the  folio by index and sheet. The index must be within the
              folio range or an exception is raised.

              tag-p -> Boolean (String)
              The tag-p method returns true if a sheet with the tag argument exists in the folio.

              find -> Sheet (String)
              The find method finds a sheet by tag. The first found sheet those tag is matched is
              returned.  In the case that multiple sheet share the same tag, the filter should be
              used. If no sheet is found the method return the nil object.

              lookup -> Sheet (String)
              The lookup method finds a sheet by tag. The first found sheet those tag is  matched
              is  returned. In the case that multiple sheet share the same tag, the filter should
              be used. If no sheet is found the  method  throws  an  exception.  This  method  is
              similar to the find method.

              filter -> Folio (String)
              The filter method return a new folio with sheets that match the argument tag. If no
              sheet is found, the folio is empty.

              reset -> none (none)
              The reset method resets the folio. The name and  information  is  unchanged  during
              this operation.

              length -> Integer (none)
              The length method returns the folio length.

              get-name -> String (none)
              The get-name method returns the folio name.

              set-name -> none (String)
              The set-name method sets the folio name.

              get-info -> String (none)
              The get-info method returns the folio info.

              set-info -> none (String)
              The set-info method sets the folio info.

              get-xref -> Xref (none|Integer|String|Integer Integer)
              The  get-xref  method  returns  a  cross-reference  table  from  the folio. Without
              argument, the whole folio is scanned and all named cells are added  in  the  cross-
              reference  table.  With  an integer argument, all cells that matches the cell index
              argument are added in the cross-reference table. With a string argument, all  cells
              that  have  the  same name are added in the table. Finally, with two arguments that
              represents the cell index and the record index are used, all cells are added in the
              table with these two coordinates.

       Index
       The  Index class is a class that maintain a cell index at the folio level. A cell index is
       composed of the sheet index, the record index and the cell index. The index object can  be
       used  to  access in a generic way a particular cell. Additionally, the folio name can also
       be stored in the index. It is possible to have multiple records that represents  the  same
       cell.

       Predicate

              index-p

       Inheritance

              Object

       Constructors

              Index (none)
              The Index constructor creates an empty index.

              Index (Integer)
              The Index constructor creates an index with a cell index as its coordinate.

              Index (Integer Integer)
              The  Integer  constructor  creates  an  index with a cell and record indexes as its
              coordinate. The first argument is the cell index. The second argument is the record
              index.

              Index (Integer Integer Integer)
              The Index constructor creates an index with a cell, record and sheet indexes as its
              coordinate. The first argument is the cell index. The second argument is the record
              index. The third argument is the sheet index.

       Methods

              add -> none (Integer|Integer Integer|Integer Integer Integer)
              The  add method adds a new index coordinate in the index object. In the first form,
              the cell index is used as the coordinate. In the second form, the cell  and  record
              indexes  are  used as the coordinate. In the third form, the cell, record and sheet
              indexes are used as the coordinate.

              reset -> none (none)
              The reset method reset the index by removing all attached coordinates.

              length -> Integer (none)
              The length method returns the index length. The  index  length  is  the  number  of
              coordinate entries in the index.

              exists-p -> Boolean (Integer|Integer Integer|Integer Integer Integer)
              The  exists-p  predicate returns true if a coordinate entry exists in the index. In
              the first form, the cell index is used as the coordinate. In the second  form,  the
              cell  and  record  indexes are used as the coordinate. In the third form, the cell,
              record and sheet indexes are used as the coordinate.

              set-index-cell -> none (Integer Integer)
              The set-index-cell method sets the cell index by position. The  first  argument  is
              the coordinate position. The second argument is the cell index to use.

              update-index-cell -> none (Integer)
              The  update-index-cell  method updates the cell index for all entries in the index.
              The argument is the new cell index to use for the update process.

              get-index-cell -> Integer (Integer)
              The get-index-cell method returns the  cell  index  for  a  particular  entry.  The
              argument is the entry position.

              set-index-record -> none (Integer Integer)
              The  set-index-record  method sets the record index by position. The first argument
              is the coordinate position. The second argument is the record index to use.

              update-index-record -> none (Integer)
              The update-index-record method updates the record index  for  all  entries  in  the
              index. The argument is the new record index to use for the update process.

              get-index-record -> Integer (Integer)
              The  get-index-record  method  returns the record index for a particular entry. The
              argument is the entry position.

              set-index-sheet -> none (Integer Integer)
              The set-index-sheet method sets the sheet index by position. The first argument  is
              the coordinate position. The second argument is the cell sheet to use.

              update-index-sheet -> none (Integer)
              The update-index-sheet method updates the sheet index for all entries in the index.
              The argument is the new sheet index to use for the update process.

              get-index-sheet -> Integer (Integer)
              The get-index-sheet method returns the sheet index  for  a  particular  entry.  The
              argument is the entry position.

       Xref
       The  Xref  class is a cross-reference class. The class maintains the association between a
       name and an index. with a particular name, an index  entry  is  created  if  it  does  not
       exists. Such entry can be later used to access the cell content by index.

       Predicate

              xref-p

       Inheritance

              Object

       Constructors

              Xref (none)
              The Xref constructor creates an empty cross-reference object.

       Methods

              add -> none (String [Integer|Integer Integer|Integer Integer Integer])
              The  add method adds a new reference in the table. The first argument is always the
              index name. In the first form, the cell index is used as  the  coordinate.  In  the
              second  form,  the cell and record indexes are used as the coordinate. In the third
              form, the cell, record and sheet indexes are used as the coordinate.

              get -> Index (Integer|String)
              The get method returns an Index object either by name or position. With an  integer
              argument, the index is obtained by position. With a string argument, the index with
              the matching name is returned.

              reset -> none (none)
              The reset method resets the cross-reference table.

              length -> Integer (none)
              The length method returns the length of the cross-reference table.

              lookup -> Index (String)
              The lookup method returns an index those name is  the  matching  argument.  If  the
              index cannot be found, an exception is raised.

              exists-p -> Boolean (String)
              The exists-p predicate returns true if an index those name is the matching argument
              exists in the cross-reference table.

              get-name -> String (Integer)
              The get-name method returns the index name by position.