🚀 go-pugleaf

In article <6725@vtserf.cc.vt.edu>, gbol@rglnext.geol.vt.edu (Gregory Lampshire) writes...
> 
> 
>I want to set up a macro 
>	\if <argument #1 is null> do this etc.
>	\else etc.
>	\fi

There are a number of ways to do this, but the following is the best.
(Best in most senses...but not in clarity!)
There are two types of syntax to check for null parameters:
\ifnull{#1}\then ... \else...\fi
\if\naught{#1}...\else...\fi
Choose the definitions that correspond to the desired syntax.

%========================================================================
%  \ifblank --- checks if parameter is blank (Spaces count as blank)
%  \ifgiven --- checks if parameter is not blank: like \ifblank\else
%  \ifnull  --- checks if parameter is null (spaces are NOT null)
%     use \ifgiven{#1}\then   ...  \else  ...  \fi   etc
\let\then\iftrue
{\catcode`\!=8 % funny catcode so ! will be a delimiter
\long\gdef\ifgiven#1\then{\Ifbl@nk#1@@@\empty!}% negative of \ifblank
\long\gdef\ifblank#1\then{\Ifbl@nk#1@@..!}% if null or spaces
\long\gdef\Ifbl@nk#1#2@#3#4!{\ifx#3#4}
\long\gdef\ifnull#1\then{\IfN@LL#1* {#1}!}% if null
\long\gdef\IfN@LL#1 #2!{\ifblank{#2}\then}
%
%
%  or.... use \if\given, \if\blank, \if\naught (\null already exists)
%  without \then.
%
\long\gdef\given#1{\fi\Ifbl@nk#1@@@\empty!}
\long\gdef\blank#1{\fi\Ifbl@nk#1@@..!}% if null or spaces
\long\gdef\naught#1{\IfN@Ught#1* {#1}!}% if null
\long\gdef\IfN@Ught#1 #2!{\blank{#2}}
\long\gdef\Ifbl@nk#1#2@#3#4!{\ifx#3#4}
}