Adding sign + betwen lines (not math mode)

Question

I edited a function about vertical mltiplication to achieve horizontal placement of the two multipliers.

I need the sign + centered between 6942 and 4628 in black color.I tried with \begin{align} but the functions for the \multiplication doesn't work .

  \documentclass{article}
\usepackage{fp,intcalc}
\begin{document}
    \def\multiplication#1#2{
        \def\answer{\FPmul\temp{#1}{#2}
            \parindent=0pt
            \FPround\temp{\temp}{0}\temp}
        \def\lineFirst{#1.#2}
        \def\linez##1##2##3{
            \intcalcMul{#1}{##2}##3}
        \def\Rule{\rule{1.3cm}{0.3pt}}
        \begin{minipage}[t]{1.5cm}
            \begin{flushright}
                \lineFirst \vspace{-3mm}
                \Rule \\
                \def\Z{\phantom{0}}
                \linez{#1}{2}\\
                \linez{#1}{1}{\Z}\\[-8pt]
                \Rule
                \answer
            \end{flushright}
    \end{minipage}}
    \multiplication{2314}{12}
    $\; \;$ 
    \multiplication{2314}{12}

\end{document}  

Answer 1

I'd use expl3 for the job. Do you really use a period for denoting multiplication?

\documentclass{article}
\usepackage{xparse,booktabs}

\ExplSyntaxOn
\NewDocumentCommand{\multiplication}{sO{c}mm}
 {
  \IfBooleanTF { #1 }
   {
    \ensuremath{ #3.#4=\int_eval:n { #3 * #4 } }
   }
   {
    \simeon_multiplication:nnn { #2 } { #3 } { #4 }
   }
 }

\seq_new:N \l__simeon_multiplication_b_seq
\seq_new:N \l__simeon_multiplication_c_seq
\int_new:N \l__simeon_multiplication_step_int

\cs_new_protected:Nn \simeon_multiplication:nnn
 {
  % store the second factor in reverse order
  \seq_set_split:Nnn \l__simeon_multiplication_b_seq { } { #3 }
  \seq_reverse:N \l__simeon_multiplication_b_seq
  % store the partial products with a padding
  \seq_clear:N \l__simeon_multiplication_c_seq
  \int_zero:N \l__simeon_multiplication_step_int
  \seq_map_inline:Nn \l__simeon_multiplication_b_seq
   {
    \seq_put_right:Nx \l__simeon_multiplication_c_seq
     {
      &\int_eval:n { #2 * ##1 }
      \prg_replicate:nn { \l__simeon_multiplication_step_int } { \__simeon_zero: }
     }
    \int_incr:N \l__simeon_multiplication_step_int
   }
  \begin{tabular}[#1]{@{}r@{}r@{}}
  \multicolumn{2}{@{}r@{}}{#2.#3} \\
  \midrule
  \seq_use:Nn \l__simeon_multiplication_c_seq { \__simeon_plus: } \\
  \midrule
  & \int_eval:n { #2 * #3 }
  \end{tabular}
 }

\cs_new_protected:Nn \__simeon_zero: { \hphantom{0} }
\cs_new_protected:Nn \__simeon_plus:
 {
  \\
  \raisebox{0.6667\normalbaselineskip}[0pt][0pt]{+\,}
  \\[-\normalbaselineskip]
 }
\ExplSyntaxOff

\begin{document}

% center align
\multiplication{2314}{12}
\multiplication{9999}{99}
\multiplication{9999}{9999}

\bigskip

% top align
\multiplication[t]{2314}{12}
\multiplication[t]{9999}{99}
\multiplication[t]{9999}{9999}

\bigskip

% bottom align
\multiplication[b]{2314}{12}
\multiplication[b]{9999}{99}
\multiplication[b]{9999}{9999}

\bigskip

% only multiplication
\multiplication*{2314}{12}\par
\multiplication*{9999}{99}\par
\multiplication*{9999}{9999}

\end{document}

A version that swaps the numbers for doing the computation, if the first is less than the second. It also works with floating point numbers (the alignment is not perfect, in this case, though, at the moment.

\documentclass{article}
\usepackage{xparse,siunitx,booktabs,multirow}

\sisetup{output-decimal-marker={,}}

\ExplSyntaxOn
\NewDocumentCommand{\multiplication}{sO{c}mm}
 {
  \group_begin:
  \sisetup { group-separator = {} }
  \tl_set:Nn \l__simeon_multiplication_do_tl { \num{#3}.\num{#4} }
  \IfBooleanTF { #1 }
   {
    \simeon_multiplication_inline:nn { #3 } { #4 }
   }
   {
    \simeon_multiplication:nnn { #2 } { #3 } { #4 }
   }
  \group_end:
 }

\tl_new:N \l__simeon_multiplication_do_tl
\tl_new:N \l__simeon_multiplication_a_tl
\tl_new:N \l__simeon_multiplication_b_tl
\seq_new:N \l__simeon_multiplication_b_seq
\seq_new:N \l__simeon_multiplication_c_seq
\int_new:N \l__simeon_multiplication_step_int
\fp_new:N \l__simeon_multiplication_result_fp

\cs_new_protected:Nn \simeon_multiplication_inline:nn
 {
  \tl_set:Nn \l__simeon_multiplication_a_tl { #1 }
  \tl_set:Nn \l__simeon_multiplication_b_tl { #2 }
  \tl_replace_once:Nnn \l__simeon_multiplication_a_tl { , } { . }
  \tl_replace_once:Nnn \l__simeon_multiplication_b_tl { , } { . }
  \ensuremath
   {
    \l__simeon_multiplication_do_tl =
    \num
     {
      \fp_eval:n
       {
        \l__simeon_multiplication_a_tl * \l__simeon_multiplication_b_tl
       }
     }
   }
 }


\cs_new_protected:Nn \simeon_multiplication:nnn
 {
  % store the second factor in reverse order
  \tl_set:Nn \l__simeon_multiplication_a_tl { #2 }
  \tl_set:Nn \l__simeon_multiplication_b_tl { #3 }
  \tl_replace_once:Nnn \l__simeon_multiplication_a_tl { , } { . }
  \tl_replace_once:Nnn \l__simeon_multiplication_b_tl { , } { . }
  \fp_set:Nn \l__simeon_multiplication_result_fp
   {
    \l__simeon_multiplication_a_tl * \l__simeon_multiplication_b_tl
   }
  \fp_compare:nTF { \l__simeon_multiplication_a_tl > \l__simeon_multiplication_b_tl }
   {
    \__simeon_multiplication:nNN { #1 } \l__simeon_multiplication_a_tl \l__simeon_multiplication_b_tl
   }
   {
    \__simeon_multiplication:nNN { #1 } \l__simeon_multiplication_b_tl \l__simeon_multiplication_a_tl
   }
 }

\cs_new_protected:Nn \__simeon_multiplication:nNN
 {
  % find the number of final zeros
  \tl_clear:N \l__simeon_multiplication_zeros_tl
  \__simeon_multiplication_zeros:NN #2 #3
  % remove the decimal separator
  \tl_remove_once:Nn #2 { . }
  \tl_remove_once:Nn #3 { . }
  % store the second factor in reverse order
  \seq_set_split:NnV \l__simeon_multiplication_b_seq { } #3
  \seq_reverse:N \l__simeon_multiplication_b_seq
  % store the partial products with a padding
  \seq_clear:N \l__simeon_multiplication_c_seq
  \int_zero:N \l__simeon_multiplication_step_int
  \seq_map_inline:Nn \l__simeon_multiplication_b_seq
   {
    \seq_put_right:Nx \l__simeon_multiplication_c_seq
     {
      &\int_eval:n { #2 * ##1 }
      \prg_replicate:nn { \l__simeon_multiplication_step_int } { \__simeon_zero: }
     }
    \int_incr:N \l__simeon_multiplication_step_int
   }
  \begin{tabular}[#1]{@{}r@{}r@{}}
  \multicolumn{2}{@{}r@{}}{\l__simeon_multiplication_do_tl} \\
  \midrule
  \multirow{\tl_count:N #3}{*}{\raisebox{\depth}{+}\,}
  \seq_use:Nn \l__simeon_multiplication_c_seq { \\ } \\
  \midrule
  & \num{ \fp_use:N \l__simeon_multiplication_result_fp }
    \l__simeon_multiplication_zeros_tl
  \end{tabular}
 }

\cs_new_protected:Nn \__simeon_zero: { \hphantom{0} }
\cs_new_protected:Nn \__simeon_plus:
 {
  \\
  \raisebox{0.66667\normalbaselineskip}[0pt][0pt]{+\,}
  \\[-\normalbaselineskip]
 }

\cs_new_protected:Nn \__simeon_multiplication_zeros:NN
 {
  \seq_set_split:NnV \l_tmpa_seq { . } #1
  \seq_set_split:NnV \l_tmpb_seq { . } #2
  \tl_set:Nx \l_tmpa_tl
   {
    \seq_item:Nn \l_tmpa_seq { 2 }
    \seq_item:Nn \l_tmpb_seq { 2 }
   }
  \tl_set:Nx \l_tmpb_tl { \fp_eval:n { #1 * #2 } }
  \seq_set_split:NnV \l_tmpa_seq { . } \l_tmpb_tl
  \tl_set:Nx \l_tmpb_tl { \seq_item:Nn \l_tmpa_seq { 2 } }
  \tl_set:Nx \l__simeon_multiplication_zeros_tl
   {
    \prg_replicate:nn { \tl_count:N \l_tmpa_tl - \tl_count:N \l_tmpb_tl } { 0 }
   }
 }

\ExplSyntaxOff

\begin{document}

% center align
\multiplication{2314}{12}\quad
\multiplication{12}{2314}\quad
\multiplication{9999}{99}\quad
\multiplication{9999}{9999}\quad
\multiplication{23,14}{1,2}\quad
\multiplication{235}{388}\quad
\multiplication{2,35}{38,8}

\bigskip

% top align
\multiplication[t]{2314}{12}\quad
\multiplication[t]{12}{2314}\quad
\multiplication[t]{9999}{99}\quad
\multiplication[t]{9999}{9999}\quad
\multiplication[t]{23,14}{1,2}

\bigskip

% bottom align
\multiplication[b]{2314}{12}\quad
\multiplication[b]{12}{2314}\quad
\multiplication[b]{9999}{99}\quad
\multiplication[b]{9999}{9999}\quad
\multiplication[b]{23,14}{1,2}

\bigskip

% only multiplication
\multiplication*{2314}{12}\par
\multiplication*{12}{2314}\par
\multiplication*{9999}{99}\par
\multiplication*{9999}{9999}\par
\multiplication*{23,14}{1,2}

\end{document}