How can I align indents for condition statements in AucTex algorithm section?

Question

If possible, I want to align condition statements like: \If, \Else, \For statements in between \begin{algorithmic} ... \end{algorithmic} section.

example:

\begin{algorithmic}[1]
\For{a for statement}                | for a for stament
    \If{some coding}                 |     if some coding    
        \State do something          |         do something  
    \EndIf                           |
\EndFor                              | 
\If{some coding}                     | if some coding
    \State do something              |      do something  
\EndIf 
\end{algorithmic}

---

Following example latex code taken from: https://tex.stackexchange.com/a/615852/127048. When I select all lines in the buffer an press (TAB indent-for-tab-command) it aligns all if else statements in the same vertical line. In python-mode indent-for-tab-command successfully align indents.

\documentclass{article}
\usepackage{algorithm}
\usepackage[noend]{algpseudocode}
\begin{document}
\begin{algorithm}
\caption{Main D Algorithm}\label{alg:cap}
\begin{algorithmic}[1]
\For{a for statement}
    \If{some coding}
    \State do something
    \ElsIf{another condition}
        \For{some condition}
            \If{another statement}
                \State do something
            \EndIf
        \EndFor
    \ElsIf{problem is here}
        \State whatever
    \EndIf
\EndFor
\end{algorithmic}
\end{algorithm}
\end{document}

After TAB indent-for-tab-command the buffer is converted into:

\documentclass{article}
\usepackage{algorithm}
\usepackage[noend]{algpseudocode}
\begin{document}
\begin{algorithm}
\caption{Main D Algorithm}\label{alg:cap}
\begin{algorithmic}[1]
    \For{a for statement}
    \If{some coding}
    \State do something
    \ElsIf{another condition}
    \For{some condition}
    \If{another statement}
    \State do something
    \EndIf
    \EndFor
    \ElsIf{problem is here}
    \State whatever
    \EndIf
    \EndFor
\end{algorithmic}
\end{algorithm}
\end{document}

Answer 1

Add the following to your init file:

(with-eval-after-load 'latex
    (add-to-list 'LaTeX-indent-environment-list '("algorithmic" current-indentation)))

That's the equivalent of the customization, but maybe you got the customization wrong somehow.

You should check the value of LaTeX-indent-environment-list and make sure that there is an algorithmic entry in it:

Value:
(("algorithmic" current-indentation)
 ("verbatim" current-indentation)
 ("verbatim*" current-indentation)
 ("filecontents" current-indentation)
 ("filecontents*" current-indentation)
 ("tabular" LaTeX-indent-tabular)
 ("tabular*" LaTeX-indent-tabular)
 ("align" LaTeX-indent-tabular)
 ("align*" LaTeX-indent-tabular)
 ("array" LaTeX-indent-tabular)
 ("eqnarray" LaTeX-indent-tabular)
 ("eqnarray*" LaTeX-indent-tabular)
 ("displaymath")
 ("equation")
 ("equation*")
 ("picture")
 ("tabbing"))

You should also check that LaTeX-indent-environment-check is set to t. That is the default, but you never know. In fact, you should probably do both of these checks in your current setup and maybe that will point out what you did wrong in the customization.

After restarting Emacs and opening the file, the indentation of the contents of an algorithmic environment should not be affected by TAB.

I have a feeling that even though this answers the current question, it is not going to be satisfactory in the long run, but I'll let you experiment and ask more questions about it later.

Answer 2

AUCTeX is able to indent conditionals better with this change. At the same time, the code in algpseudocode.el was adjusted to take advantage of this feature.

If I take your example, indent the line with \caption and \begin{algorithmic}[1] manually by hitting TAB, then put point before \For and hit M-q, I get this:

\documentclass{article}
\usepackage{algorithm}
\usepackage[noend]{algpseudocode}
\begin{document}
\begin{algorithm}
  \caption{Main D Algorithm}\label{alg:cap}
  \begin{algorithmic}[1]
    \For{a for statement}
      \If{some coding}
        \State do something
      \ElsIf{another condition}
        \For{some condition}
          \If{another statement}
            \State do something
          \EndIf
        \EndFor
      \ElsIf{problem is here}
        \State whatever
      \EndIf
    \EndFor
  \end{algorithmic}
\end{algorithm}
\end{document}

Just wait for next AUCTeX release from ELPA which should happen soon, and you don't need to rely on external tools anymore.

Answer 3

I found a solution using https://github.com/raxod502/apheleia and latexindent.pl together.

localSettings.yaml for latexindent.pl its issue:

defaultIndent: "    "
specialBeginEnd:
  If:
    begin: '\\If'
    middle: '\\ElsIf'
    end: '\\EndIf'
    lookForThis: 1
  specialBeforeCommand: 1

Installing latexindent.pl:

mkdir ~/bin && cd ~/bin
git clone https://github.com/cmhughes/latexindent.pl.git
chmod +x latexindent.pl/latexindent.pl
export PATH=~/bin:$PATH

latexindent: should be executable and its path exist in PATH

#!/bin/bash
cp $HOME/localSettings.yaml .
~/bin/latexindent.pl/latexindent.pl -l $1

---

apheleia will run latexindent automatically when a .tex file is opened.