[Tex/LaTex] How to sort a list numerically

#enumeratedescriptionlistssorting

Basically, I want to create a summary for a history class. Therefore a lot of years occur throughout the lectures.

Does LaTeX allow to sort a list if I set it up like in the following example?

\begin{description}
  \item[1912] Something good happened
  \item[1923] Something bad happened
  \item[1901] Something terrible happened
\end{description}

Is it possible that LaTeX recognizes the number and reorders it correctly?

Desired output:

1901 Something terrible happened

1912 Something good happened

1923 Something bad happened

LaTeX is able to do so in the bib, so can it be extended somehow?

Best Answer

This approach automatically orders the items by year or any other number, by using an external list on an .csv file.

\documentclass{article}
\usepackage{filecontents} % To create an external .csv file
\begin{filecontents}{\jobname.csv}
Order, Text
1912, Something good happened.
1923, Something bad happened.
1901, Something terrible happened.
\end{filecontents}

\usepackage{datatool}
\DTLloaddb{externalcsv}{\jobname.csv}

\begin{document}

\begin{enumerate}
\DTLsort{Order=ascending}{externalcsv}%
\DTLforeach{externalcsv}{\myorder=Order, \mytext=Text}{\item[\myorder.]\mytext}
\end{enumerate}

\end{document}

Output

Related Solutions

[Tex/LaTex] How to sort an alphanumeric list

I didn't look at Charles's code because I wanted to see how difficult it would be to implement a generic sorting macro that was expandable. It turns out that it's more or less straight-forward to do in a continuation-passing style.

\documentclass{article}
\usepackage{etoolbox}
\makeatletter
% #1 - comparator
% #2 - token list to sort
\newcommand\sort[2]{%
        \ifstrempty{#2}
        {}% else
        {%
                \sort@begin#1{}#2\sort@s\sort@begin
        }%
}

% helpers
\def\sort@s{\sort@s}
\def\ifsort@s#1{%
        \ifx\sort@s#1%
                \expandafter\@firstoftwo
        \else
                \expandafter\@secondoftwo
        \fi
}

% #1 - comparator
% #2 - tokens processed so far
% #3 - smallest token so far
% #4 - rest of the list
\def\sort@begin#1#2#3#4\sort@begin{%
        \ifsort@s{#4}
        {%
                \sortend{#3}%
                \sort#1{#2}%
        }% else
        {%
                \sort@go#1{#2}{#3}#4\sort@go
        }%
}

% #1 - comparator
% #2 - tokens processed so far
% #3 - smallest token so far
% #4 - token under consideration
% #5 - rest of the list
\def\sort@go#1#2#3#4#5\sort@go{%
        #1{#3}{#4}{\sort@output#1{#2}{#5}}%
}
% #1 - comparator
% #2 - tokens processed so far
% #3 - rest of the list
% #4 - smaller of the two tokens
% #5 - larger of the two tokens
\def\sort@output#1#2#3#4#5{%
        \ifsort@s{#3}
        {%
                \sortoutput{#4}%
                \sort#1{#2{#5}}%
        }% else
        {%
                \sort@begin#1{#2{#5}}{#4}#3\sort@begin
        }%
}

\def\sort@numlt#1#2#3{%
        \ifnumcomp{#1}<{#2}
        {#3{#1}{#2}}% else
        {#3{#2}{#1}}%
}

\def\sort@numgt#1#2#3{%
        \ifnumcomp{#1}>{#2}
        {#3{#1}{#2}}% else
        {#3{#2}{#1}}%
}

\def\sort@alpha#1#2#3{%
        \ifnumcomp{\pdfstrcmp{#1}{#2}}<{0}
        {#3{#1}{#2}}% else
        {#3{#2}{#1}}%
}

\newcommand*\sortnumlt{\sort\sort@numlt}
\newcommand*\sortnumgt{\sort\sort@numgt}
\newcommand*\sortalpha{\sort\sort@alpha}
\makeatother

% Change these to change out the sort outputs.
\newcommand*\sortoutput[1]{#1, }
\newcommand*\sortend[1]{#1.}
\begin{document}
\sortnumgt{87632147{55}9{8/2}}

\sortalpha{{Goodbye}{Cruel}{World}}

\renewcommand*\sortoutput[1]{#1}
\renewcommand*\sortend[1]{#1}
\edef\temp{\sortnumlt{87632147{55}9}}
\texttt{\meaning\temp}
\end{document}

I hope the code is readable. I tried to document the arguments to each function. In particular, the first argument to \sort is a comparator control sequence that must take three arguments. The first two are the two elements of the following list to compare and the third is the continuation. Basically, the comparator should expand to either #3{#1}{#2} or #3{#2}{#1} depending on #1 being "less than" #2.

I've implemented three such comparators. The first two compare lists of numbers whereas the third does alphanumeric string comparison using \pdfstrcmp. Since the number comparisons use \ifnumcomp from etoolbox, you can use arbitrary arithmetic expressions for the elements, hence {8/2} in the list.

Finally, to show that this is expandable (at least it is whenever the comparator, \sortoutput, and \sortend are), \temp is defined using \edef and its meaning is typeset to ensure that it has been set to the appropriate value: macro:->12346778955.

Note that it would also be straight-forward to thread \sortoutput and \sortend through all of these macros so that multiple \sorts could be used in the same expansion. I just didn't think about adding those until I had written all of the rest of the code (more or less).

Note further that this is selection sort and thus would take Θ(n²) time, even in the best case. However, this being TeX and it having to construct the token lists for each argument each time, I think this implementation is actually Θ(n³) time. So don't try it on large lists.

[Tex/LaTex] Enumerated description list

EDIT

Comment of Ben:

Could I also have a separate listclass, say enumdescript, such that I don't have to apply the settings manually everytime I want to use one of those lists?

The package enumitem provides a simple way to define you own list environments. The command \newlist in combination with setlist are the relavant commands. With \newlist you can define you own list and via \setlist set the settings. In the following example I define the environment enumdescript with the depth 2. Both commands are well explained in the documentation.

\documentclass{scrbook}

\usepackage{enumitem}
\newcounter{descriptcount}
\newlist{enumdescript}{description}{2}
\setlist[enumdescript,1]{%
  before={\setcounter{descriptcount}{0}%
          \renewcommand*\thedescriptcount{\alph{descriptcount}}}
  ,font=\bfseries\stepcounter{descriptcount}\thedescriptcount~
}
\setlist[enumdescript,2]{%
  before={\setcounter{descriptcount}{0}%
          \renewcommand*\thedescriptcount{\roman{descriptcount}}}
  ,font=\bfseries\stepcounter{descriptcount}\thedescriptcount~
}
\begin{document}

\begin{enumdescript}
   \item item one
   \item item two
   \item[Some Text] item three
   \begin{enumdescript}
      \item item one
      \item item two
      \item[Some Text] item three
   \end{enumdescript}
   \item item four
   \item item five
\end{enumdescript}
\end{document}

ORIGNIAL Answer:

Use the package enumitem in the newest version:

\documentclass{scrbook}

\usepackage{enumitem}
\newcounter{descriptcount}
\renewcommand*\thedescriptcount{\alph{descriptcount}}
\begin{document}

\begin{description}[%
  before={\setcounter{descriptcount}{0}},%
  ,font=\bfseries\stepcounter{descriptcount}\thedescriptcount~]
   \item item one
   \item item two
   \item[Some Text] item three
\end{description}

\end{document}

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] How to sort an alphanumeric list

[Tex/LaTex] Enumerated description list

Related Question