TeXForm on table, how to make empty cells?

Question

I have the code:

l = {{1, 2, 3}, {1, 2, 3}};
l = Append[l, PadLeft[{1}, 3, Null]];
TeXForm[TableForm[l]]

Returns

\begin{array}{ccc}
 1 & 2 & 3 \\
 1 & 2 & 3 \\
 \text{Null} & \text{Null} & 1 \\
\end{array}

But I am looking to get the last row as

  & & 1 \\

What is the way to do that, I was hoping that Null would be removed. I tried empty string, but it still leads having \text{} in the output.

Answer 1

You can create an object that TeXForm will treat as an empty string:

MakeBoxes[foo, TraditionalForm] ^:= RowBox[{}]

Then:

TeXForm[TableForm[{{1, 2, 3}, {1, 2, 3}, {foo, foo, 1}}]]

produces:

\begin{array}{ccc}
 1 & 2 & 3 \\
 1 & 2 & 3 \\
  &  & 1 \\
\end{array}

which renders as:

\begin{array}{ccc} 1 & 2 & 3 \\ 1 & 2 & 3 \\ & & 1 \\ \end{array}

Answer 2

Since the invention of 0 by the Indians to save the place between to ciphers in decimal strings against neclection or overwriting, there has to be something in TeX to hold the place

l = {{1, 2, 3}, {1, 2, 3}};
l = Append[l, PadLeft[{1}, 3, Esc sq Esc]];

TeXForm[TableForm[l]]

\begin{array}{ccc}
 1 & 2 & 3 \\
 1 & 2 & 3 \\
 \square  & \square  & 1 \\
\end{array}

l

I justwas remembering there are other invisible characters treated as symbols, that don'produce \text in TeX. But now the browser interface here is clueless with naked unicode, so that I have it deliver as string.

In[82]:= 
TeXForm[ {{1,2,4},{a,b,c},{\[LetterSpace],\[LetterSpace],1}}//TableForm]


  "\begin{array}{ccc}  1 & 2 & 4 \\  a & b & c \\  \unicode{f754} &
  \unicode{f754} & 1 \\ \end{array}"