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EMPTY()
Determine if the result of an expression is empty
------------------------------------------------------------------------------
Syntax
EMPTY(<exp>) --> lEmpty
Arguments
<exp> is an expression of any data type.
Returns
EMPTY() returns true (.T.) if the expression results in an empty value;
otherwise, it returns false (.F.). The criteria for determining whether
a value is considered empty depends on the data type of <exp> according
to the following rules:
List of Empty Values
------------------------------------------------------------------------
Data Type Contents
------------------------------------------------------------------------
Array Zero-length
Character Spaces, tabs, CR/LF, or ("")
Numeric 0
Date Null (CTOD(""))
Logical False (.F.)
Memo Same as character
NIL NIL
------------------------------------------------------------------------
Description
The EMPTY() function has a number of uses. You can use it to determine
if a user entered a value into a Get object before committing changes to
a database file. It can also determine whether a formal parameter is
NIL or unsupplied. In addition, it can test an array for zero-length.
Notes
. Space characters: The EMPTY() function treats carriage
returns, line feeds, and tabs as space characters and removes these
as well.
Examples
. These examples illustrate use of EMPTY() against several
different data types:
? EMPTY(SPACE(5)), EMPTY("") // Result: .T. .T.
? EMPTY(0), EMPTY(CTOD("")) // Result: .T. .T.
? EMPTY(.F.), EMPTY(NIL) // Result: .T. .T.
. This example uses EMPTY() to determine whether the user
entered a value into the first Get object before writing the new
value to the database file:
LOCAL cCust := SPACE(15), nAmount := 0
USE Sales NEW
@ 10, 10 GET cCust
@ 11, 10 GET nAmount PICTURE "999.99"
READ
//
IF !EMPTY(cCust)
APPEND BLANK
REPLACE Sales->Cust WITH cCust, Sales->Amount ;
WITH nAmount
ENDIF
. This example uses EMPTY() as part of the VALID clause to force
the user to enter data into the current Get object:
LOCAL cCode := SPACE(5)
@ 2, 5 SAY "Enter code" GET cCode VALID !EMPTY(cCode)
READ
Files Library is CLIPPER.LIB.
See Also:
LEN()
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