Importing Tabular Cells from Text File

Question

Suppose I want to build a table which looks as follows:

\begin{tabular}{ccc}  
 1.23 & 2.98 & Apple \\  
-3.78 & 4.01 & Banana \\  
\end{tabular}

However, the numbers in the table are given in a separate text file, say "file.txt", with the content

1.23 & 2.98
-3.78 & 4.01

Is there a simple way to input the cells from "file.txt" into a larger table? I tried

\begin{tabular}{ccc}
\input{file.txt} & \multirow{2}{*}{Apple \\ Banana} \\
\end{tabular}

but this fails (unsurprisingly). I also tried to use minipages - this works in the above toy example but fails in more realistic ones (most importantly, I could not align inputs from different files).

Any comments/suggestions welcome!

EDIT Here's a MWE. The file "file.txt" is as mentioned above. "file2.txt" has the following contents:

1.23 & 2.98 \\
-3.78 & 4.01 \\

(obviously, both "file.txt" and "file2.txt" should be saved in the directory of the tex file). Code for MWE:

\documentclass{article}
\usepackage{multirow}

\begin{document}

% Approach using minipage (works, but looks ugly)
\begin{minipage}{0.4\textwidth}
\begin{tabular}{cc}
\input{file2.txt} 
\end{tabular}
\end{minipage}
\begin{minipage}{0.2\textwidth}
\begin{tabular}{c}
Apple \\ Banana
\end{tabular}
\end{minipage}

% Approach mentioned above (fails)
\begin{tabular}{ccc}
\input{file.txt} & \multirow{2}{*}{Apple \\ Banana} \\
\end{tabular}

\end{document}

Answer 1

You can define \preparetable macro which prepares data for the table:

\preparetable {file.txt} {Apple, Banana}

and then use this in the table environment:

\begin{tabular}{ccc} \usetable \end{tabular}

The whole example follows:

\documentclass{article}      

\newread\infile
\def\preparetable#1#2{\bgroup \openin\infile=#1
   \let\\=\relax \gdef\usetable{}\preparetableA #2,,}
\def\preparetableA #1,{\if,#1,\egroup \closein\infile \else \read\infile to\tmp
  \xdef\usetable{\usetable \tmp & #1 \\}\expandafter\preparetableA\fi}

\begin{document}

\preparetable {file.txt} {Apple, Banana}
\begin{tabular}{ccc} \usetable \end{tabular}

\end{document}

Answer 2

A solution similar to wipet's, but using expl3. Longer, but quite readable once one has gotten some practice.

\begin{filecontents*}{\jobname.dat}
 1.23 & 2.98
-3.78 & 4.01
\end{filecontents*}

\documentclass{article}
\usepackage{xparse}
\usepackage{array}
\newcolumntype{C}{>{$}c<{$}}

\ExplSyntaxOn
\NewDocumentCommand{\addcolumn}{mm}
 {
  % #1 is the file to read, #2 the list of items to add, separated by \\
  \fabian_addcolumn:nn { #1 } { #2 }
 }

% some variables
\seq_new:N \l__fabian_additions_seq
\tl_new:N \l__fabian_table_body_tl
\tl_new:N \l__fabian_item_tl
\ior_new:N \g_fabian_import_stream

\cs_new_protected:Npn \fabian_addcolumn:nn #1 #2
 {
  % clear the variable containing the table body
  \tl_clear:N \l__fabian_table_body_tl
  % create a sequence from the second argument
  \seq_set_split:Nnn \l__fabian_additions_seq { \\ } { #2 }
  % start reading the file
  \ior_open:Nn \g_fabian_import_stream { #1 }
  % at each line ...
  \ior_map_inline:Nn \g_fabian_import_stream
   {
    % 1. detach the leftmost item from the sequence
    \seq_pop_left:NN \l__fabian_additions_seq \l__fabian_item_tl
    % 2. add the line and a trailing &
    \tl_put_right:Nn \l__fabian_table_body_tl { ##1 & }
    % 3. add the current item
    \tl_put_right:NV \l__fabian_table_body_tl \l__fabian_item_tl
    % 4. add the trailing \\
    \tl_put_right:Nn \l__fabian_table_body_tl { \\ }
   }
  % deliver the result
  \tl_use:N \l__fabian_table_body_tl
 }

\ExplSyntaxOff

\begin{document}

\begin{tabular}{CCl}
\addcolumn{\jobname.dat}{Apple\\Banana}
\end{tabular}

\end{document}

Here's the version for the case the data file has trailing \\ on each line; instead of adding directly the read line, we first store it into a token list and replace \\ by &.

\begin{filecontents*}{\jobname.dat}
 1.23 & 2.98 \\
-3.78 & 4.01 \\
\end{filecontents*}

\documentclass{article}
\usepackage{xparse}
\usepackage{array}
\newcolumntype{C}{>{$}c<{$}}

\ExplSyntaxOn
\NewDocumentCommand{\addcolumn}{mm}
 {
  \fabian_addcolumn:nn { #1 } { #2 }
 }

\seq_new:N \l__fabian_additions_seq
\tl_new:N \l__fabian_table_body_tl
\tl_new:N \l__fabian_item_tl
\tl_new:N \l__fabian_temp_tl
\ior_new:N \g_fabian_import_stream

\cs_new_protected:Npn \fabian_addcolumn:nn #1 #2
 {
  \tl_clear:N \l__fabian_table_body_tl
  \seq_set_split:Nnn \l__fabian_additions_seq { \\ } { #2 }
  \ior_open:Nn \g_fabian_import_stream { #1 }
  \ior_map_inline:Nn \g_fabian_import_stream
   {
    \seq_pop_left:NN \l__fabian_additions_seq \l__fabian_item_tl
    \tl_set:Nn \l__fabian_temp_tl { ##1 }
    \tl_replace_once:Nnn \l__fabian_temp_tl { \\ } { & }
    \tl_put_right:NV \l__fabian_table_body_tl \l__fabian_temp_tl
    \tl_put_right:NV \l__fabian_table_body_tl \l__fabian_item_tl
    \tl_put_right:Nn \l__fabian_table_body_tl { \\ }
   }
  \tl_use:N \l__fabian_table_body_tl
 }

\ExplSyntaxOff

\begin{document}

\begin{tabular}{CCl}
\addcolumn{\jobname.dat}{Apple\\Banana}
\end{tabular}

\end{document}