This is a reference to a null item, such as may be returned across the COM interface to represent a null value. A null might be returned as the result of a .NET method or as the value of an empty cell in a spreadsheet
⎕NULL may be used in any context that accepts a namespace reference, in particular:
- As the argument to a defined function
- As an item of an array.
- As the argument to those primitive functions that take character data arguments, for example: =, ≠, ≡, ≢, ,, ⍴, ⊃, ⊂
Example
'EX'⎕WC'OLEClient' 'Excel.Application' WB←EX.Workbooks.Open 'simple.xls' (WB.Sheets.Item 1).UsedRange.Value2 [Null] [Null] [Null] [Null] [Null] [Null] Year [Null] [Null] [Null] [Null] 1999 2000 2001 2002 [Null] [Null] [Null] [Null] [Null] Sales 100 76 120 150 [Null] [Null] [Null] [Null] [Null] Costs 80 60 100 110 [Null] [Null] [Null] [Null] [Null] Margin 20 16 20 40
To determine which of the cells are filled, you can compare the array with ⎕NULL.
⎕NULL≢¨(WB.Sheets.Item 1).UsedRange.Value2 0 0 0 0 0 0 1 0 0 0 0 1 1 1 1 0 0 0 0 0 1 1 1 1 1 0 0 0 0 0 1 1 1 1 1 0 0 0 0 0 1 1 1 1 1