LaTeX3 case inside \equal

Question

I have a LaTeX document where I have defined a switch case command using LaTeX3 syntax. I am using the case inside the \equal condition of an \ifthenelse command. However, I keep getting the wrong result; seems to me that inside the \equal, the switch case cannot be expandend.

What I am doing wrong? In the MWE below I am expecting "Function is A :)" but got "Function is B :(":

\documentclass{book}
\usepackage{xparse}
\usepackage{ifthen}

\ExplSyntaxOn
\newcommand\caseswitch[2]{
  \str_case_e:nn{#1}{#2}
}
\ExplSyntaxOff

\newcommand\mycommand[1]{
  \caseswitch{#1}{
    {A}{Aaa}
    {B}{Bbb}
  }
}

\begin{document}

% expected "Function is A :)" but got "Function is B :("
\ifthenelse{\equal{\mycommand{A}}{Aaa}}{Function is A :)}{Function is B :(}

% another version - does not work too
%\caseswitch{\mycommand{A}}{{Aaa}{Function is A :)}{Bbb}{Function is B :(}}

\end{document}

Answer 1

An interesting case of the spurious space syndrome: you're comparing Aaa with  Aaa  (with two spaces around the string).

\documentclass{book}
\usepackage{xparse}
\usepackage{ifthen}

\ExplSyntaxOn
\newcommand\caseswitch[2]{
  \str_case_e:nn{#1}{#2}
}
\ExplSyntaxOff

\newcommand\mycommand[1]{% <--- HERE
  \caseswitch{#1}{
    {A}{Aaa}
    {B}{Bbb}
  }% <--- HERE
}

\begin{document}

% expected "Function is A :)" but got "Function is B :("
\ifthenelse{\equal{\mycommand{A}}{Aaa}}{Function is A :)}{Function is B :(}

% another version - does not work too
\caseswitch{\mycommand{A}}{{Aaa}{Function is A :)}{Bbb}{Function is B :(}}

\end{document}

I'd use the simpler

\ExplSyntaxOn
\cs_set_eq:NN \caseswitch \str_case_e:nn
\ExplSyntaxOff

and also the reimplementation of \ifthenelse I proposed elsewhere on the site (see the link for examples of use).

\documentclass{book}

\ExplSyntaxOn

%%% Expandable reimplementation of \ifthenelse
\NewExpandableDocumentCommand{\xifthenelse}{mmm}
 {
  \bool_if:nTF { #1 } { #2 } { #3 }
 }

\cs_new_eq:NN \numtest     \int_compare_p:n
\cs_new_eq:NN \oddtest     \int_if_odd_p:n
\cs_new_eq:NN \fptest      \fp_compare_p:n
\cs_new_eq:NN \dimtest     \dim_compare_p:n
\cs_new_eq:NN \deftest     \cs_if_exist_p:N
\cs_new_eq:NN \namedeftest \cs_if_exist_p:c
\cs_new_eq:NN \eqdeftest   \token_if_eq_meaning_p:NN
\cs_new_eq:NN \streqtest   \str_if_eq_p:ee
\cs_new_eq:NN \emptytest   \tl_if_empty_p:n
\cs_new_eq:NN \blanktest   \tl_if_blank_p:n
\cs_new_eq:NN \boolean     \legacy_if_p:n
\cs_new:Npn \modetest #1
 {
  \str_case:nnF { #1 }
   {
    {h}{\mode_if_horizontal_p:}
    {v}{\mode_if_vertical_p:}
    {m}{\mode_if_math_p:}
    {i}{\mode_if_inner_p:}
   }
   {\c_false_bool}
 }
\cs_new:Npn \enginetest #1
 {
  \str_case:nnF { #1 }
   {
    {luatex}{\sys_if_engine_luatex_p:}
    {pdftex}{\sys_if_engine_pdftex_p:}
    {ptex}{\sys_if_engine_ptex_p:}
    {uptex}{\sys_if_engine_uptex_p:}
    {xetex}{\sys_if_engine_xetex_p:}
   }
   {\c_false_bool}
 }

% a utility command
\cs_set_eq:NN \caseswitch \str_case_e:nn

\ExplSyntaxOff

\newcommand\mycommand[1]{%
  \caseswitch{#1}{
    {A}{Aaa}
    {B}{Bbb}
  }%
}

\begin{document}

% expected "Function is A :)" but got "Function is B :("
\xifthenelse{\streqtest{\mycommand{A}}{Aaa}}{Function is A :)}{Function is B :(}

% another version - does not work too
\caseswitch{\mycommand{A}}{{Aaa}{Function is A :)}{Bbb}{Function is B :(}}

\end{document}

Answer 2

If you are not in Expl3 you need to be aware of spaces at end of line. Also you never really need \ifthenelse especially if you are already using expl3 which has far better control constructs.

\documentclass{book}


\ExplSyntaxOn
\cs_set_eq:NN \caseswitch \str_case_e:nn

\newcommand\mycommand[1]{
  \caseswitch{#1}{
    {A}{Aaa}
    {B}{Bbb}
  }
}
\ExplSyntaxOff

\begin{document}


\caseswitch{\mycommand{A}}{{Aaa}{Function is A :)}{Bbb}{Function is B :(}}

\end{document}