.IFNDEF-.ELSE-.ENDC

Perform conditional processing

.IFNDEF data_element
   [. . .
source_1
   . . .]
[.ELSE
   . . .
[source_2
   . . .]]
.ENDC

Arguments

data_element

One of the following:

A defined macro
A data declaration in the current routine
A data declaration in a class (imported or otherwise)
A data declaration in a structure, defined at any level and visible at that moment in processing
An enumeration

source_1

(optional) One or more lines of source code.

source_2

(optional) One or more lines of source code.

Discussion

The .IFNDEF compilation control directive indicates that the statements that follow are to be compiled if the specified data element has not previously been defined.

The source_1 lines of code are compiled only if the specified variable or identifier is not defined prior to the .IFNDEF directive. If the .ELSE directive is present, the source_2 lines of code are compiled only if the specified variable or identifier is defined prior to the .IFDEF directive.

You can use one or more of the .ELSE, .IFT, .IFF, and .IFTF directives within an .IFNDEF conditional block. These conditional compilation control directives can be nested.

The .ENDC directive must always close an .IFNDEF conditional block.

Examples

The following example shows a simple conditional compilation control operation.

.define TTCHN           ,1
proc
    open(TTCHN, o, "tt:")
.ifndef NO_STATS
    writes(TTCHN, "some stats")         ;This code will be compiled.
.else

    .
    . ;Don't write stats
    .
.endc

The next example shows nesting of the .IFNDEF conditional compilation control directive.

.define TTCHN           ,1
.define SHOWTBLA
    .
    .
    .
proc
    open(TTCHN, o, "tt:")
    .
    .
    .
.ifndef NO_TABLES                               ;This code won't be compiled.
.ifndef SHOWTBLA
    writes(TTCHN,  "No information available for Table A")
.else
    writes(TTCHN, "Table A")                    ;This code will be compiled.
.endc
.endc
    .
    .
    .
end