Hacker’s Guide to Visual FoxPro
An irreverent look at how Visual FoxPro really works. Tells you the inside scoop on every command, function, property, event and method of Visual FoxPro.
AELEMENT(), ASUBSCRIPT()
These two functions convert between the two numbering schemes for array elements: continuous element numbering and row/column numbering. Because some array functions use one form and others need the other form, these functions are pretty useful.
AELEMENT() takes an array, a row and, optionally, a column and returns the corresponding element number. ASUBSCRIPT() takes an array and an element number and returns either the row or the column.
Usage
nElement = AELEMENT( ArrayName, nRow [, nCol ] )
|
Parameter |
Value |
Meaning |
|
ArrayName |
Array Name |
The array in which you want to convert from row, column notation to element notation. It's necessary to specify the array because the shape of the array determines the conversion. |
|
nRow |
Numeric |
The row number of the item for which the element number is desired. |
|
nCol |
Numeric |
The column number of the item for which the element number is desired. |
|
Omitted |
Treat ArrayName as a one-dimensional array and return nRow. |
|
|
nElement |
Numeric |
The element number of the specified element. If the array is one-dimensional or nCol is omitted, nRow is returned. |
Example
DIMENSION aTest[5], a2DTest[4,2]
? AELEMENT(aTest, 3) && returns 3
? AELEMENT(a2DTest, 3) && returns 3
? AELEMENT(a2DTest, 3, 2) && returns 6
Usage
nSubscript = ASUBSCRIPT( ArrayName, nElement, nSubscript )
|
Parameter |
Value |
Meaning |
|
ArrayName |
Array Name |
The array in which you want to convert from element notation to row, column notation. It's necessary to specify the array because the shape of the array determines the conversion. |
|
nElement |
Numeric |
The element number of the item for which either the row or column number is desired. |
|
nSubscript |
1 |
Return the row subscript of the element. In a one-dimensional array, this is the same as the element number. |
|
2 |
Return the column subscript of the element. In a one-dimensional array, gives an error message. |
ASUBSCRIPT() is particularly useful when working with ASCAN(), which returns an element number. We often want to get a particular element out of the same row of the array as the element found by ASCAN(). ASUBSCRIPT() gives us the row number, which we can then use to grab the relevant item.
Watch out for one thing. When nElement isn’t a valid element number for the array, you get an error. Frankly, we think we’d prefer if ASUBSCRIPT() returned 0 in that case and let us deal with it.
Example
DIMENSION aTest[5],a2DTest[4,2]
? ASUBSCRIPT(aTest, 3, 1) && returns 3
? ASUBSCRIPT(a2DTest, 3, 1) && returns 2
? ASUBSCRIPT(a2DTest, 3, 2) && returns 1
* The next example assumes SearchItem has a value
* that can be found in the array.
? ASUBSCRIPT(a2DTest, ASCAN(a2DTest, SearchItem), 1)