deferred class interface COLLECTION2[E]
   --
   -- Abstract definition of a 2 dimensional collection of elements
   -- of type E.
   --
   -- The SmartEiffel standard library (SmartEiffel/lib/base) provides two
   -- implementations of COLLECTION2[E]: ARRAY2[E] and FIXED_ARRAY2[E].
   -- All implementations have exactly the same behavior. Switching
   -- from one implementation to another only change the memory used
   -- and the execution time.
   --

feature(s) from COLLECTION2
   -- Indexing:

   lower1: INTEGER
      -- Lower index bounds.


   lower2: INTEGER
      -- Lower index bounds.


   line_minimum: INTEGER
      -- Equivalent of lower1.


   column_minimum: INTEGER
      -- Equivalent of lower2.


   upper1: INTEGER
      -- Upper index bounds.


   upper2: INTEGER
      -- Upper index bounds.


   line_maximum: INTEGER
      -- Equivalent of upper1.


   column_maximum: INTEGER
      -- Equivalent of upper2.


feature(s) from COLLECTION2
   -- Reading:

   item (line, column: INTEGER): E
      require
         valid_index(line,column)

feature(s) from COLLECTION2
   -- Writing:

   put (element: like item; line, column: INTEGER)
      require
         valid_index(line,column)
      ensure
         item(line,column) = element

   force (element: like item; line, column: INTEGER)
      -- Put element at position (line,column). Collection is
      -- resized first when (line,column) is not inside current
      -- bounds. New bounds are initialized with default values.

      require
         line >= 0;
         column >= 0
      ensure
         item(line,column) = element;
         count >= old count

feature(s) from COLLECTION2
   -- Index validity:

   valid_line (line: INTEGER): BOOLEAN
      ensure
         Result = (lower1 <= line and line <= upper1)

   valid_index1 (line: INTEGER): BOOLEAN
      ensure
         Result = (lower1 <= line and line <= upper1)

   valid_column (column: INTEGER): BOOLEAN
      ensure
         Result = (lower2 <= column and column <= upper2)

   valid_index2 (column: INTEGER): BOOLEAN
      ensure
         Result = (lower2 <= column and column <= upper2)

   valid_index (line, column: INTEGER): BOOLEAN
      ensure
         Result = (valid_line(line) and valid_column(column))

feature(s) from COLLECTION2
   -- Counting:

   count1: INTEGER
      -- Size of the first dimension.

      ensure
         Result = upper1 - lower1 + 1

   line_count: INTEGER
      -- Equivalent of count1.


   count2: INTEGER
      -- Size of the second dimension.

      ensure
         Result = upper2 - lower2 + 1

   column_count: INTEGER

   count: INTEGER
      -- Total number of elements.

      ensure
         Result = line_count * column_count

feature(s) from COLLECTION2   swap (line1, column1, line2, column2: INTEGER)
      -- Swap the element at index (line1,column1) with the
      -- the element at index (line2,column2).

      require
         valid_index(line1,column1);
         valid_index(line2,column2)
      ensure
         item(line1,column1) = old item(line2,column2);
         item(line2,column2) = old item(line1,column1);
         count = old count

   set_all_with (v: like item)
      -- Set all item with value v.

      ensure
         count = old count

   clear_all
      -- Set all items to default values.

      ensure
         count = old count;
         all_default

feature(s) from COLLECTION2
   -- Creating or initializing:

   from_collection2 (model: COLLECTION2[like item])
      --  Uses model to initialize Current.

      require
         model /= Void
      ensure
         count1 = model.count1;
         count2 = model.count2

   from_model (model: COLLECTION[COLLECTION[E]])
      -- The model is used to fill line by line Current.
      -- Assume all sub-collections of model have the same
      -- number of lines.

      require
         model /= Void
      ensure
         count1 = model.count;
         count2 > 0 implies count2 = model.first.count

feature(s) from COLLECTION2
   -- Looking and comparison:

   all_default: BOOLEAN
      -- Do all items have their type's default value?


   same_as (other: COLLECTION2[E]): BOOLEAN
      -- Unlike is_equal, this feature can be used to compare
      -- distinct implementation of COLLECTION2.

      require
         other /= Void
      ensure
         Result implies standard_same_as(other)

feature(s) from COLLECTION2
   -- Printing:

   fill_tagged_out_memory
      -- Append a viewable information in tagged_out_memory in
      -- order to affect the behavior of out, tagged_out, etc.


feature(s) from COLLECTION2
   -- Miscellaneous features:

   occurrences (elt: E): INTEGER
      -- Number of occurrences using equal.
      -- See also fast_occurrences to chose the apropriate one.

      ensure
         Result >= 0

   fast_occurrences (elt: E): INTEGER
      -- Number of occurrences using =.
      -- See also occurrences to chose the apropriate one.

      ensure
         Result >= 0

   has (x: like item): BOOLEAN
      -- Search if a element x is in the array using equal.
      -- See also fast_has to chose the apropriate one.


   fast_has (x: like item): BOOLEAN
      --  Search if a element x is in the array using =.


   replace_all (old_value, new_value: like item)
      -- Replace all occurrences of the element old_value by new_value
      -- using equal for comparison.
      -- See also fast_replace_all to choose the apropriate one.

      ensure
         count = old count;
         occurrences(old_value) = 0

   fast_replace_all (old_value, new_value: like item)
      -- Replace all occurrences of the element old_value by new_value
      -- using operator = for comparison.
      -- See also replace_all to choose the apropriate one.

      ensure
         count = old count;
         fast_occurrences(old_value) = 0

   sub_collection2 (line_min, line_max, column_min, column_max: INTEGER): like Current
      -- Create a new object using selected area of Current.

      require
         valid_index(line_min,column_min);
         valid_index(line_max,column_max)
      ensure
         Result /= Void

   set_area (element: like item; line_min, line_max, column_min, column_max: INTEGER)
      -- Set all the elements of the selected area rectangle with element.

      require
         valid_index(line_min,column_min);
         valid_index(line_max,column_max)
      ensure
         count = old count



end of deferred COLLECTION2[E]