+function tests for any printing character except space.
+In the ASCII character set, this includes the following characters:
+.sp
+.Bl -column \&000_``0''__ \&000_``0''__ \&000_``0''__ \&000_``0''__ \&000_``0''__
+.It \&041\ ``!'' \t042\ ``"'' \t043\ ``#'' \t044\ ``$'' \t045\ ``%''
+.It \&046\ ``&'' \t047\ ``''' \t050\ ``('' \t051\ ``)'' \t052\ ``*''
+.It \&053\ ``+'' \t054\ ``,'' \t055\ ``-'' \t056\ ``.'' \t057\ ``/''
+.It \&060\ ``0'' \t061\ ``1'' \t062\ ``2'' \t063\ ``3'' \t064\ ``4''
+.It \&065\ ``5'' \t066\ ``6'' \t067\ ``7'' \t070\ ``8'' \t071\ ``9''
+.It \&072\ ``:'' \t073\ ``;'' \t074\ ``<'' \t075\ ``='' \t076\ ``>''
+.It \&077\ ``?'' \t100\ ``@'' \t101\ ``A'' \t102\ ``B'' \t103\ ``C''
+.It \&104\ ``D'' \t105\ ``E'' \t106\ ``F'' \t107\ ``G'' \t110\ ``H''
+.It \&111\ ``I'' \t112\ ``J'' \t113\ ``K'' \t114\ ``L'' \t115\ ``M''
+.It \&116\ ``N'' \t117\ ``O'' \t120\ ``P'' \t121\ ``Q'' \t122\ ``R''
+.It \&123\ ``S'' \t124\ ``T'' \t125\ ``U'' \t126\ ``V'' \t127\ ``W''
+.It \&130\ ``X'' \t131\ ``Y'' \t132\ ``Z'' \t133\ ``['' \t134\ ``\''
+.It \&135\ ``]'' \t136\ ``^'' \t137\ ``_'' \t140\ ```'' \t141\ ``a''
+.It \&142\ ``b'' \t143\ ``c'' \t144\ ``d'' \t145\ ``e'' \t146\ ``f''
+.It \&147\ ``g'' \t150\ ``h'' \t151\ ``i'' \t152\ ``j'' \t153\ ``k''
+.It \&154\ ``l'' \t155\ ``m'' \t156\ ``n'' \t157\ ``o'' \t160\ ``p''
+.It \&161\ ``q'' \t162\ ``r'' \t163\ ``s'' \t164\ ``t'' \t165\ ``u''
+.It \&166\ ``v'' \t167\ ``w'' \t170\ ``x'' \t171\ ``y'' \t172\ ``z''
+.It \&173\ ``{'' \t174\ ``|'' \t175\ ``}'' \t176\ ``~''
+.El