[Pixel]<Imaging>SACFormulas>begaf.ecs!1

sL=BEGAF(C)
$[Begin atomic formula predicate. sL=1 if C is a legal first character
of an atomic formula, otherwise sL=0.]
safe BEGAF.
(1) if DIGIT(C) eq 1 or LETTER(C) eq 1 or C eq $=- or C eq $=+
then sL=1 else sL=0; return..