## ALP Programming Guide and Reference

[prev][next][parent][TOC]

### .ERRDEF/.ERRNDEF (Error if Symbol Defined/Not Defined)

The .ERRDEF and .ERRNDEF directives test whether a symbol has been defined.

Syntax

    . ERRDEF   Identifier
        or
    . ERRNDEF   Identifier

Remarks

If Identifier is defined as a label, a variable, or a symbol, the .ERRDEF directive produces an error. If you have not defined Identifier, .ERRNDEF produces an error. When Identifier is a forward reference, the assembler considers it undefined on the first pass and defined on the second pass.

Example

In this example, .ERRDEF ensures that SYMBOL is not defined before entering the blocks, and .ERRNDEF ensures that you defined SYMBOL somewhere within the blocks.

    . ERRDEF      SYMBOL
    IFDEF        CONFIG1
                 .
                 .     SYMBOL   EQU   0
                 .
    ENDIF
    IFDEF        CONFIG2
                 .
                 .    SYMBOL    EQU   1
                 .
    ENDIF
    . ERRNDEF      SYMBOL