Null object: Difference between revisions

=={{header|COBOL}}==

Works with GnuCOBOL 2.0

<lang COBOL> identification division.

program-id. null-objects.

remarks. test with cobc -x -j null-objects.cob

data division.

working-storage section.

01 thing-not-thing usage pointer.

*> call a subprogram

*> with one null pointer

*> an omitted parameter

*> and expect void return (omitted)

*> and do not touch default return-code (returning nothing)

procedure division.

call "test-null" using thing-not-thing omitted returning nothing

goback.

end program null-objects.

*> Test for pointer to null (still a real thing that takes space)

*> and an omitted parameter, (call frame has placeholder)

*> and finally, return void, (omitted)

identification division.

program-id. test-null.

data division.

linkage section.

01 thing-one usage pointer.

01 thing-two pic x.

procedure division using

thing-one

optional thing-two

returning omitted.

if thing-one equal null then

display "thing-one pointer to null" upon syserr

end-if

if thing-two omitted then

display "no thing-two was passed" upon syserr

end-if

goback.

end program test-null.</lang>

{{out}}

<pre>

prompt$ cobc -x -j null-objects.cob

thing-one pointer to null

no thing-two was passed

</pre>