UNASSIGNED() |
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The UNASSIGNED() function tests whether a variable is unassigned.
Format
UNASSIGNED(var)
where
All QMBasic variables except those in common blocks are initially unassigned. Any attempt to use the contents of the variable in an expression would cause a run time error until such time as a value has been stored in it. The UNASSIGNED() function allows a program to test whether a variable is unassigned, returning true (1) if it is unassigned or (0) if it is assigned.
Example
SUBROUTINE VALIDATE(ACCOUNT.CODE, ERROR) BEGIN CASE CASE UNASSIGNED(ACCOUNT.CODE) ERROR = 1 CASE ACCOUNT.CODE MATCHES '3N-5N' ERROR = 2 ...etc... CASE 1 ERROR = 0 END CASE RETURN END
This program fragment validates an account code. The use of the UNASSIGNED() function prevents an abort if the variable has not been assigned.
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