Formula:HideIfEmpty

noli hanc formulam uti; utere huius loco {{#if: ... }} et {{#ifeq: ... }}.

vide w:en:Wikipedia:HiddenStructure pro iustificatione.

quomodo huius loci uti {{#if: ... }} et {{#ifeq: ... }}:

parametrum		{{{1}}}	{{#if:{{{1}}}|A|B}}	{{#if:{{{1|}}}|A|B}}	{{#ifeq:{{{1|}}}|{{{1|-}}}|A|B}}
praesens:	{{formula|abc}}	abc	A	A	A
vacuum:	{{formula|}}		B	B	A
absens:	{{formula}}	{{{1}}}	A	B	B

plures instructiones inveniuntur in mw:Help:Extension:ParserFunctions.