newcommand with parameter blank or zero

Question

i read code in other topic: definited newcommand selectTask.

IF TaskOne/TaskTwo = blank is ok.

Now i want to edit IF TaskOne/TaskTwo = blank or zero (0).

Please help update this code:

\newcommand{\selectTask}[2]{%
  \if\relax#1\relax
    \if\relax#2\relax
      \selectTaskA % 00 TaskOne = TaskTwo=blank => How if blank or zero?
    \else
      \selectTaskB % 01 TaskOne =blank,TaskTwo=!=blank
    \fi
  \else
    \if\relax#2\relax
      \selectTaskC % 10  TaskOne !=blank, TaskTwo=blank
    \else
      \selectTaskD % 11 TaskOne = TaskTwo!=blank
    \fi
  \fi
}

Please help if data = zero or blank. Thank in advance

Adding to @DavidCarlisle's first comment: A better test would be \if\relax\detokenize{#1}\relax. — Skillmon, Jun 13, 2019 at 20:29
There is also \if\empty#1\relax, but for best results use something like \def\@tempa{#1} to do comparisons. — John Kormylo, Jun 13, 2019 at 20:34
If the arguments will always be numeric (or blank), \newcommand{\selectTask}[2]{\ifnum9=#19\relax \ifnum9=#29\relax \selectTaskA \else \selectTaskB \fi \else \ifnum9=#29\relax \selectTaskC \else \selectTaskD \fi \fi } — Steven B. Segletes, Jun 13, 2019 at 20:38
A test for "blankness", i.e., only space tokens or no tokens at all, could be: \long\def\firstoftwo#1#2{#1}\long\def\secondoftwo#1#2{#2}...\if\relax\detokenize\expandafter{\firstoftwo#1{}.}\relax\expandafter\firstoftwo\else\expandafter\secondoftwo\fi{<blank>}{<not blank>} — Ulrich Diez, Jun 14, 2019 at 12:24

David Carlisle · Accepted Answer · 2019-06-14 06:52:47Z

\if\relax#1\relax would be true if the expansion of #1 results in something that starts with any non-character. \if\relax\hbox{abc}\relax for example would test as true (and typeset abc).

this uses \ifx tests which do not expand the tested tokens.

\def\tmpempty{}
\def\tmpzero{0}

\newcommand{\selectTask}[2]{%
  \def\tmp{#1}\ifx\tmp\tmpempty\let\tmp\tmpzero\fi
  \def\tmpb{#2}\ifx\tmpb\tmpempty\let\tmpb\tmpzero\fi
  \ifx\tmp\tmpzero
    \ifx\tmpb\tmpzero
      \show\selectTaskA % 00 TaskOne = TaskTwo=blank => How if blank or zero?
    \else
      \show\selectTaskB % 01 TaskOne =blank,TaskTwo=!=blank
    \fi
  \else
    \ifx\tmpb\tmpzero
      \show\selectTaskC % 10  TaskOne !=blank, TaskTwo=blank
    \else
      \show\selectTaskD % 11 TaskOne = TaskTwo!=blank
    \fi
  \fi
}



\selectTask{}{}%A
\selectTask{0}{}%A
\selectTask{}{x}%B
\selectTask{0}{x}%B
\selectTask{x}{}%C
\selectTask{x}{0}%C
\selectTask{x}{y}%D





\stop

egreg · Accepted Answer · 2019-06-13 20:45:04Z

Here's an implementation according to your idea: the first argument is tested if blank, if it is the following macro is called with 0 argument; similarly the second argument is tested. Then we do a string case choice.

\documentclass{article}
\usepackage{xparse}

\ExplSyntaxOn

\NewExpandableDocumentCommand{\selectTask}{mm}
 {
  \latexforti_select_task:nn { #1 } { #2 }
 }

\cs_new:Nn \latexforti_select_task:nn
 {
  \tl_if_blank:nTF { #1 }
   {
    \__latexforti_select_task_a:nn { 0 } { #2 }
   }
   {
    \__latexforti_select_task_a:nn { #1 } { #2 }
   }
 }
\cs_new:Nn \__latexforti_select_task_a:nn
 {
  \tl_if_blank:nTF { #2 }
   {
    \__latexforti_select_task_b:nn { #1 } { 0 }
   }
   {
    \__latexforti_select_task_b:nn { #1 } { #2 }
   }
 }
\cs_new:Nn \__latexforti_select_task_b:nn
 {
  \str_case:nn { #1#2 }
   {
    {00}{\selectTaskA}
    {01}{\selectTaskB}
    {10}{\selectTaskC}
    {11}{\selectTaskD}
   }
 }

\ExplSyntaxOff

\newcommand{\selectTaskA}{I'm task A}
\newcommand{\selectTaskB}{I'm task B}
\newcommand{\selectTaskC}{I'm task C}
\newcommand{\selectTaskD}{I'm task D}

\begin{document}

\selectTask{0}{0} --- \selectTask{}{0} -- \selectTask{0}{}

\selectTask{0}{1} --- \selectTask{}{1}

\selectTask{1}{0} --- \selectTask{1}{}

\selectTask{1}{1}

\end{document}

An implementation with more classical methods (but arguments cannot be { } as in the previous one).

\documentclass{article}

\makeatletter

\newcommand{\selectTask}[2]{%
  \expandafter\latexforti@select\expandafter
    {\number0#1\expandafter}\expandafter{\number0#2}%
}
\newcommand{\latexforti@select}[2]{%
  \ifcase\numexpr#1*2+#2\relax % the arguments are binary digits!
    \selectTaskA
  \or
    \selectTaskB
  \or
    \selectTaskC
  \or
    \selectTaskD
  \fi
}
\makeatother

\newcommand{\selectTaskA}{I'm task A}
\newcommand{\selectTaskB}{I'm task B}
\newcommand{\selectTaskC}{I'm task C}
\newcommand{\selectTaskD}{I'm task D}

\begin{document}

\selectTask{0}{0} --- \selectTask{}{0} -- \selectTask{0}{}

\selectTask{0}{1} --- \selectTask{}{1}

\selectTask{1}{0} --- \selectTask{1}{}

\selectTask{1}{1}

\end{document}

Steven B. Segletes · Accepted Answer · 2019-06-13 20:42:09Z

If the arguments are only allowed to be blank or numeric, you can use an \ifnum comparison.

\documentclass[]{scrartcl}
\def\selectTaskA{00}
\def\selectTaskB{01}
\def\selectTaskC{10}
\def\selectTaskD{11}

\newcommand{\selectTask}[2]{%
  \ifnum9=#19\relax
    \ifnum9=#29\relax
      \selectTaskA
    \else
      \selectTaskB
    \fi
  \else
    \ifnum9=#29\relax
      \selectTaskC
    \else
      \selectTaskD
    \fi
  \fi
}
\begin{document}
\selectTask{}{}\\
\selectTask{0}{}\\
\selectTask{}{0}\\
\selectTask{0}{0}\\
\selectTask{}{1}\\
\selectTask{1}{}\\
\selectTask{1}{1}
\end{document}

Ulrich Diez · Accepted Answer · 2019-06-14 13:25:29Z

This is a variant which is expansion-based, i.e., does without whatsoever temporary assignments. Besides this it does without any \if..-primitives (which avoids problems in case the arguments themselves contain unbalanced \if../\else/\fi).

\documentclass[a4paper]{article}
\usepackage{textcomp}
\makeatletter
%%----------------------------------------------------------------------
%% Check whether argument is empty:
%%......................................................................
%% \UD@CheckWhetherNull{<Argument which is to be checked>}%
%%                     {<Tokens to be delivered in case that argument
%%                       which is to be checked is empty>}%
%%                     {<Tokens to be delivered in case that argument
%%                       which is to be checked is not empty>}%
%% The gist of this macro comes from Robert R. Schneck's \ifempty-macro:
%% <https://groups.google.com/forum/#!original/comp.text.tex/kuOEIQIrElc/lUg37FmhA74J>
\newcommand\UD@CheckWhetherNull[1]{%
  \romannumeral0\expandafter\@secondoftwo\string{\expandafter
  \@secondoftwo\expandafter{\expandafter{\string#1}\expandafter
  \@secondoftwo\string}\expandafter\@firstoftwo\expandafter{\expandafter
  \@secondoftwo\string}\expandafter\expandafter\@firstoftwo{ }{}%
  \@secondoftwo}{\expandafter\expandafter\@firstoftwo{ }{}\@firstoftwo}%
}%
%%----------------------------------------------------------------------
%% Check whether argument is blank (empty or only space tokens):
%%......................................................................
%% -- Take advantage of the fact that TeX discards space tokens when
%%    "fetching" _un_delimited arguments: --
%% \UD@CheckWhetherBlank{<Argument which is to be checked>}%
%%                      {<Tokens to be delivered in case that
%%                        argument which is to be checked is blank>}%
%%                      {<Tokens to be delivered in case that argument
%%                        which is to be checked is not blank}%
\newcommand\UD@CheckWhetherBlank[1]{%
  \romannumeral\expandafter\expandafter\expandafter\@secondoftwo
  \expandafter\UD@CheckWhetherNull\expandafter{\@firstoftwo#1{}.}%
}%
%%----------------------------------------------------------------------
%% Check whether argument is blank (empty or only space tokens) or
%% consists only of a _single_ token "0" (charcode 48(dec), catcode 12(dec))
%%......................................................................
\newcommand\UD@GobbleToExclam{}\long\def\UD@GobbleToExclam#1!{}%
\newcommand\UD@forkzero{}\long\def\UD@forkzero#1!!0!#2#3!!!!{#2}%
\newcommand\UD@zerofork[3]{%
  \expandafter\UD@CheckWhetherNull\expandafter{\UD@GobbleToExclam#1!}{%
    \UD@forkzero!#1!0!{#3}%<-case #1 is empty/has no tokens
                !!#1!{#2}%<-case #1 = "0"
                !!0!{#3}%<-case #1 something else without exclamation mark
                !!!!%
  }{#3}%<-case #1 = something else with exclamation-mark.
}%
\newcommand\UD@CheckWhetherBlankOrZero[1]{%
  \romannumeral0\UD@CheckWhetherBlank{#1}{%
    \@firstoftwo{\expandafter}{} \@firstoftwo
  }{%
     \UD@zerofork{#1}%
     {\@firstoftwo{\expandafter}{} \@firstoftwo}%
     {\@firstoftwo{\expandafter}{} \@secondoftwo}%
  }%
}%
%%----------------------------------------------------------------------
%% \selectTask
%%......................................................................
\newcommand{\selectTask}[2]{%
  \UD@CheckWhetherBlankOrZero{#1}{%
    \UD@CheckWhetherBlankOrZero{#2}{% <blank or zero> = either spaces or a single "0" or no tokens at all
      \selectTaskA % #1 = #2 = <blank or zero>
    }{%
      \selectTaskB % #1 = <blank or zero>; #2 =/= <blank or zero>
    }%
  }{%
    \UD@CheckWhetherBlankOrZero{#2}{%
      \selectTaskC % #1 =/= <blank or zero>; #2 = <blank or zero>
    }{%
      \selectTaskD % #1 =/= <blank or zero>; #2 =/= <blank or zero>
    }%
  }%
}%
\newcommand{\selectTaskA}{%
  Task A---%
  \string##1 \textit{\textlangle blank or zero\textrangle } 
  and
  \string##2 \textit{\textlangle blank or zero\textrangle }%
  .%
}
\newcommand{\selectTaskB}{%
  Task B---%
  \string##1 \textit{\textlangle blank or zero\textrangle } 
  and
  \string##2 not \textit{\textlangle blank or zero\textrangle }%
  .%
}
\newcommand{\selectTaskC}{%
  Task C---%
  \string##1 not \textit{\textlangle blank or zero\textrangle } 
  and
  \string##2 \textit{\textlangle blank or zero\textrangle }%
  .%
}
\newcommand{\selectTaskD}{%
  Task D--- %
  \string##1 not \textit{\textlangle blank or zero\textrangle } 
  and
  \string##2 not \textit{\textlangle blank or zero\textrangle }%
  .%
}
\makeatother

\parindent=0pt
\parskip=\baselineskip
\addtolength\oddsidemargin{-1.5cm}
\addtolength\evensidemargin{-1.5cm}
\addtolength\textwidth{3cm}

\begin{document}

\verb*|\selectTask{0}{0}|: \selectTask{0}{0}\\
\verb*|\selectTask{  }{0}|: \selectTask{  }{0}\\
\verb*|\selectTask{0}{  }|: \selectTask{0}{  }\\
\verb*|\selectTask{  }{  }|: \selectTask{  }{  }\\
\verb*|\selectTask{}{0}|: \selectTask{}{0}\\
\verb*|\selectTask{0}{}|: \selectTask{0}{}\\
\verb*|\selectTask{}{}|: \selectTask{}{}\\
\verb*|\selectTask{}{  }|: \selectTask{}{  }\\
\verb*|\selectTask{  }{}|: \selectTask{  }{}

\verb*|\selectTask{0}{1}|: \selectTask{0}{1}\\
\verb*|\selectTask{  }{1}|: \selectTask{  }{1}\\
\verb*|\selectTask{}{1}|: \selectTask{}{1}

\verb*|\selectTask{1}{0}|: \selectTask{1}{0}\\
\verb*|\selectTask{1}{  }|: \selectTask{1}{  }\\
\verb*|\selectTask{1}{}|: \selectTask{1}{}

\verb*|\selectTask{1}{1}|: \selectTask{1}{1}

\textbf{BUT:}

\verb*|\selectTask{00}{00}|: \selectTask{00}{00}

\verb*|\selectTask{ 0 }{ 0 }|: \selectTask{ 0 }{ 0 }

\let\implicitzero=0%
\def\expandtospace{ }%
\verb*|\let\implicitzero=0|\\
\verb*|\def\myspace{ }|\\
\verb*|\selectTask{\implicitzero}{\implicitzero}|:\\ \selectTask{\implicitzero}{\implicitzero}

\verb*|\selectTask{\expandtospace}{\expandtospace}|:\\ \selectTask{\expandtospace}{\expandtospace}

\end{document}

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