putting spaces within text block

Question

I have a block of text that I would like to automatically break in blocks of equal length. Something like what \num does with numbers.

What I need is a definition for what I called \makeBlocks. The MWE below should output: aaaaa bbbbb ccccc ddddd followed by abc def ghi

\documentclass{article}

\newcommand{\makeBlocks}[1]{???}

\begin{document}
\makeBlocks{5}{aaaaabbbbbcccccddddd} 
followed by
\makeBlocks{3}{abcdefghi}
\end{document}

Answer 1

Here's an implementation with l3regex:

\documentclass{article}
\usepackage{xparse,l3regex}
\ExplSyntaxOn

\NewDocumentCommand\makeBlocks{mm}
 {
  \geoff_makeblocks:nn { #1 } { #2 }
 }

\tl_new:N \l_geoff_blocks_input_tl

\cs_new_protected:Npn \geoff_makeblocks:nn #1 #2
 {
  \tl_set:Nn \l_geoff_blocks_input_tl { #2 }
  %\tl_reverse:N \l_geoff_blocks_input_tl
  \regex_replace_all:nnN { (.{0,#1}) } { \1 \c{,} } \l_geoff_blocks_input_tl
  \regex_replace_once:nnN { \c{,} \c{,} \Z } { } \l_geoff_blocks_input_tl
  %\tl_reverse:N \l_geoff_blocks_input_tl
  \tl_use:N \l_geoff_blocks_input_tl
 }

\ExplSyntaxOff

\begin{document}

\makeBlocks{3}{abcdef}

\makeBlocks{3}{abcdefg}

\makeBlocks{3}{abcdefghi}

\makeBlocks{5}{aaaaabbbbbccccc}

\end{document}

This counts starting from the left. If you want to start counting from the right, just reverse twice the token list, by uncommenting the two \tl_reverse:N lines. Here's what you'd get:

If you want a normal space between blocks, just change the two \regex lines into

\regex_replace_all:nnN { (.{0,#1}) } { \1 \cS\  } \l_geoff_blocks_input_tl
\regex_replace_once:nnN { \cS. \cS. \Z } { } \l_geoff_blocks_input_tl

---

A “full featured” macro that starts either from left or from right (this with the *-variant) and accepts the separator as optional argument (default a space).

\documentclass{article}
\usepackage{xparse,l3regex}
\ExplSyntaxOn

\NewDocumentCommand\makeBlocks{s O{~} m m }
 {
  \IfBooleanTF{#1}
   {
    \geoff_makeblocks:nnnn { #2 } { #3 } { #4 } { \__geoff_from_right: }
   }
   {
    \geoff_makeblocks:nnnn { #2 } { #3 } { #4 } { }
   }
 }

\tl_new:N \l_geoff_blocks_input_tl
\tl_new:N \l_geoff_block_separator_tl

\cs_new_protected:Npn \geoff_makeblocks:nnnn #1 #2 #3 #4
 {
  \tl_set:Nn \l_geoff_block_separator_tl { #1 }
  \tl_set:Nn \l_geoff_blocks_input_tl { #3 }

  #4 % this will be nothing or \tl_reverse:N \l_geoff_blocks_input_tl

  % search blocks of #2 tokens and put the separator after them
  \regex_replace_all:nnN
   { (.{#2}) } % search
   { \1 \u{l_geoff_block_separator_tl} } % replace
   \l_geoff_blocks_input_tl % in this list

  % if the number of tokens is a multiple of #2, one too much
  % separator is inserted, remove it
  \regex_replace_once:nnN
   { \u{l_geoff_block_separator_tl} \Z } % search
   { } % replace
   \l_geoff_blocks_input_tl % in this list

  #4

  \tl_use:N \l_geoff_blocks_input_tl
 }

\cs_new:Npn \__geoff_from_right:
 {
  \tl_reverse:N \l_geoff_blocks_input_tl
 }

\ExplSyntaxOff

\begin{document}

From left: \makeBlocks{3}{abcdef}

From left: \makeBlocks{3}{abcdefg}

From right: \makeBlocks*{3}{abcdefgh}

With different separator: \makeBlocks[ x ]{3}{abcdefghi}

With different number: \makeBlocks{5}{aaaaabbbbbccccc}

\end{document}

Answer 2

You could use the xstring package:

Notes:

• This is an enhanced version of the solution at Using \newcommand to format numbers/strings according to a pattern.
• There is a limit in this code of 400 characters, so please adjust the ending value of the \foreach as desired.
• By default the split is done from the left. If you desire the split to be from the right, you need to pass in the first optional parameter with something other than L.
• The separator is defined in \Separator so a simple \renewcommand would allow you to change that.

Code:

\documentclass{article}
\usepackage{xstring}
\usepackage{pgf,pgffor}

\newcommand*{\StringLength}{}%
\newcommand*{\FirstOutputStringLength}{}%
\newcommand*{\TempStringA}{}%
\newcommand*{\TempStringB}{}%
\newcommand*{\Separator}{\,}%
\newcommand*{\makeBlocks}[3][L]{%
    \edef\TempStringA{#3}%
    \IfStrEq{#1}{L}{%
        \foreach \x in {1,...,100} {%
            \StrLeft{\TempStringA}{#2}%
            \StrGobbleLeft{\TempStringA}{#2}[\TempStringB]%
            \xdef\TempStringA{\TempStringB}%
            \IfStrEq{\TempStringA}{}{\breakforeach}{\Separator}%
        }%
    }{%
        \StrLen{\TempStringA}[\StringLength]%
        \IfEq{\StringLength}{0}{}{%
            \pgfmathtruncatemacro{\FirstOutputStringLength}{mod(\StringLength,#2)}%
            \IfEq{\FirstOutputStringLength}{0}{%
                \xdef\TempStringB{\TempStringA}%
            }{%
                \StrLeft{\TempStringA}{\FirstOutputStringLength}\Separator%
                \StrGobbleLeft{\TempStringA}{\FirstOutputStringLength}[\TempStringB]%
            }%
        }%
        \makeBlocks[L]{#2}{\TempStringB}%
    }%
}
\begin{document}
\begin{tabular}{cll}
    Num of Char    & \multicolumn{1}{c}{Left} & \multicolumn{1}{c}{Right} \\
    5 & \makeBlocks{5}{AB1234567890}   & \makeBlocks[R]{5}{AB1234567890}\\
    5 & \makeBlocks{5}{AB123456789}    & \makeBlocks[R]{5}{AB123456789}\\
    5 & \makeBlocks{5}{AB12345678}     & \makeBlocks[R]{5}{AB12345678}\\
    5 & \makeBlocks{5}{AB1234567}      & \makeBlocks[R]{5}{AB1234567}\\
    5 & \makeBlocks{5}{AB12}           & \makeBlocks[R]{5}{AB12}\\
    5 & \makeBlocks{5}{AB}             & \makeBlocks[R]{5}{AB}\\
    5 & \makeBlocks{5}{A}              & \makeBlocks[R]{5}{A}\\ [2.0ex]
    4 & \makeBlocks{4}{AB1234567890}   & \makeBlocks[R]{4}{AB1234567890}\\
    3 & \makeBlocks{3}{AB123456789}    & \makeBlocks[R]{3}{AB123456789}\\
    2 & \makeBlocks{2}{AB12345678}     & \makeBlocks[R]{2}{AB12345678}\\
    1 & \makeBlocks{1}{AB1234567}      & \makeBlocks[R]{1}{AB1234567}\\
\end{tabular}

\bigskip
\renewcommand{\Separator}{-}%
With different separator: 

\makeBlocks{4}{AB1234567890}

\makeBlocks{1}{AB1234567890}

\end{document}