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Null object: Difference between revisions
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<lang lisp>(ns-unmap *ns* 'foo)</lang>
=={{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>
=={{header|Common Lisp}}==
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