Null Item R←⎕NULL
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