Using \notblank in etoolbox's \ifboolexpr statment

Question

As the title says, I am currently trying to use etoolbox's \ifboolexpr statment on \notblank conditions but I am having issues with it. The code concerned looks like this :

\ifboolexpr{%
  test {\notblank{\Temp@Temp@Text@a}} or %
  test {\notblank{\Temp@Temp@Text@b}} or %
  test {\notblank{\Temp@Temp@Text@c}}    %
}%
{}{}%

It however generates a bunch of errors. Even trying something like this does not quite seem to work any better :

\ifboolexpr{%
  test {\notblank{}} or %
  test {\notblank{}} or %
  test {\notblank{}}    %
}%
{}{}%

The maximum I am able to use without issues is (given as a MWE. To reproduce my issues, just substitute the \ifbookexpr statment) :

\documentclass[10pt,a4paper,titlepage,twoside,onecolumn]{report}
\RequirePackage{etoolbox}

\makeatletter
\def\Temp@Temp@Text@a{testa}
\def\Temp@Temp@Text@b{testb}
\def\Temp@Temp@Text@c{testc}

\makeatother

\begin{document}

\makeatletter

\ifboolexpr{%
  test {} or %
  test {} or %
  test {}    %
}%
{true}{false}%

\makeatother

\end{document}

So my question is :

• What am I doing wrong ?
• How to solve it ?

Answer 1

The documentation of etoolbox states that the argument to \ifblank and to \notblank is not expanded. Therefore \notblank{\xyz} will return "true" no matter what's the definition of \xyz.

If you want complete expansion you have to ask for it explicitly, for example

\documentclass[10pt,a4paper,titlepage,twoside,onecolumn]{report}
\usepackage{etoolbox}

\begin{document}

\makeatletter

\def\Temp@Temp@Text@a{testa}
\def\Temp@Temp@Text@b{testb}
\def\Temp@Temp@Text@c{testc}

\begingroup\edef\x{\endgroup
  \noexpand\ifboolexpr{%
    test {\noexpand\notblank{\Temp@Temp@Text@a}} or 
    test {\noexpand\notblank{\Temp@Temp@Text@b}} or 
    test {\noexpand\notblank{\Temp@Temp@Text@c}}    
  }}\x{\typeout{true}}{\typeout{false}}%

\def\Temp@Temp@Text@a{}
\def\Temp@Temp@Text@b{}
\def\Temp@Temp@Text@c{}

\begingroup\edef\x{\endgroup
  \noexpand\ifboolexpr{%
    test {\noexpand\notblank{\Temp@Temp@Text@a}} or 
    test {\noexpand\notblank{\Temp@Temp@Text@b}} or 
    test {\noexpand\notblank{\Temp@Temp@Text@c}}    
  }}\x{\typeout{true}}{\typeout{false}}%

\makeatother

\end{document}

The first instance returns true, while the second one returns false.

Answer 2

The catoptions package has exactly what you need without further code. \xifblankFT means fully expanded not blank. There is also \oifblankFT, meaning one-step expanded not blank.

\documentclass{report}
\usepackage{catoptions}
\def\vgap{\par\bigskip}

\begin{document}
\def\tempa{testa}
\def\tempb{testb}
\def\tempc{testc}

First test (true):
\ifexprTF{%
  test {\xifblankFT{\tempa}} or
  test {\xifblankFT{\tempb}} or
  test {\xifblankFT{\tempc}}
}{
  true
}{
  false
}

\vgap
\def\tempa{}
\def\tempb{}
\def\tempc{}

Second test (false):
\ifexprTF{%
  test {\xifblankFT{\tempa}} or
  test {\xifblankFT{\tempb}} or
  test {\xifblankFT{\tempc}}
}{
  true
}{
  false
}

\def\tempd{x}

\vgap
Third test (false):
\ifexprTF{%
  ( test {\xifblankTF{\tempa}} or test {\xifblankTF{\tempb}} )
  and
  ( test {\xifblankFT{\tempc}} and test {\xifblankFT{\tempd}} )
}{
  true
}{
  false
}

\vgap
\def\tempe{00}
\newif\iftestbool

Fourth test (true):
\ifexprTF{%
  ( switch {tempe} or bool {testbool} )
  and
  (  ( test {\xifblankTF{\tempc}} and not test {\xifblankTF{\tempd}} )
     or
     ( test {\xifstrcmpTF\tempa\tempb} or not test {\ifxTF\tempc\tempd} )
  )
}{
  true
}{
  false
}
\end{document}

This type of boolean calculus is expensive. You only need to look at the tracelog to confirm this assertion. 99 percent of the time you can do with a much simpler test. For example, since \xifstrcmpFT is expandable, we have an economical test:

\def\do#1{\ifx\do#1\relax\else+\xifstrcmpFT{#1}{}01\expandafter\do\fi}
\ifnum0=\numexpr0\do\tempa\tempb\tempc\tempd\do
  true
\else
  false
\fi