[Tex/LaTex] Code is a mess because I cannot indent inside a for loop in the algorithm

algorithmicxalgorithmsindentation

I have a for loop in my algorithm and I can't get latex to properly indent the pseudocode inside it. It's just a mess at the moment, it won't even put the code in the for loop on separate lines.

\documentclass[a4paper,12pt,times,numbered,print,index]{Classes/PhDThesisPSnPDF}

\RequirePackage[left=37mm,right=30mm,top=35mm,bottom=30mm]{geometry}
\RequirePackage{libertine} 
\RequirePackage[small,bf]{caption}
\RequirePackage[labelsep=space,tableposition=top]{caption} 
\usepackage{subfig}  
\usepackage{amsfonts}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{braket}
\usepackage{algorithm}% http://ctan.org/pkg/algorithms
\usepackage{algpseudocode}% http://ctan.org/pkg/algorithmicx
\usepackage{algorithm}% http://ctan.org/pkg/algorithms
\usepackage{algpseudocode}% http://ctan.org/pkg/algorithmicx

\begin{document}
\begin{algorithm}
\caption{Generate transition matrix for one-dimensional quantum walk}\label{tran_mat_1d_qw}
\begin{algorithmic}[1]
\Procedure{generateTransitionMatrix}{$steps$}
    \State $numElements \gets steps * 4 + 2$
    \State $transitionMat \gets numElements \times numElements$ MATRIX

    \BlankLine
    \State $col \gets 0$
    \For {$i = 1 \to (steps * 2) - 1$}
        \State row \gets i * 2$
        \STATE\hspace{\algorithmicindent} transitionMat[row,      col]        \gets $1$
        \STATE\hspace{\algorithmicindent} transitionMat[row,      col + 1]    \gets $1$
        \STATE\hspace{\algorithmicindent} transitionMat[row + 5,  col]        \gets $1$
        \STATE\hspace{\algorithmicindent} transitionMat[row + 5,   col + 1]   \gets $-1$
    \ENDFOR
\end{algorithmic}
\end{algorithm}
\end{document}

Best Answer

I don't know how \BlankLines is defined, so I've removed that. If you want an unnumbered, empty line use \Statex.

There are numerous problems with your code.

\gets must be placed in math mode, i.e. it needs to be within a pair of dollar signs. When outside math mode it generates the missing $ inserted error.
In the first \State in the for loop you have forgotten the opening $, there is just the one at the end of the line.
Macros are case sensitive, this means that \State is not the same as \STATE. The algorithmicx package defines the former, so change all \STATE to \State. Similarly, \ENDFOR should be \EndFor (read the documentation for algorithmicx/algpseudocode).

These mistakes generate Undefined control sequence errors.
You have to close the \Procedure with an \EndProcedure. This generates an error from algorithmicx saying Some blocks are not closed!!!.

Other comments:

When writing words (as opposed to variables, such as x), use either \text{the word(s)} or \mathrm{the word(s)}, which typesets them in a roman font.
You use \times one place, and * other places, use \times consistently.
Concerning your preamble: You load caption twice, with different arguments, why? Add all the arguments to a single call of caption. You also load both algorithm and algpseudocode twice, which is pointless.

Finally, the convention is to use \usepackage and not \RequirePackage in preambles, though they do the same thing. See e.g. https://tex.stackexchange.com/a/19933/586

In the code below I removed the unused packages.

enter image description here

\documentclass{article}
\usepackage{algorithm}% http://ctan.org/pkg/algorithms
\usepackage{algpseudocode}% http://ctan.org/pkg/algorithmicx

\begin{document}
\begin{algorithm}
\caption{Generate transition matrix for one-dimensional quantum walk}\label{tran_mat_1d_qw}
\begin{algorithmic}[1]
\Procedure{generateTransitionMatrix}{$\mathrm{steps}$}
    \State $\mathrm{numElements} \gets \mathrm{steps} \times 4 + 2$
    \State $\mathrm{transitionMat} \gets \mathrm{numElements} \times \mathrm{numElements}$ MATRIX
    \State $\mathrm{col} \gets 0$
    \For {$i = 1 \to (\mathrm{steps} \times 2) - 1$}
        \State $\mathrm{row} \gets i \times 2$
        \State\hspace{\algorithmicindent} $\mathrm{transitionMat[row,      col]       } \gets 1$
        \State\hspace{\algorithmicindent} $\mathrm{transitionMat[row,      col + 1]}    \gets 1$
        \State\hspace{\algorithmicindent} $\mathrm{transitionMat[row + 5,  col]       } \gets 1$
        \State\hspace{\algorithmicindent} $\mathrm{transitionMat[row + 5,   col + 1]}   \gets -1$
    \EndFor
\EndProcedure
\end{algorithmic}
\end{algorithm}
\end{document}

Related Solutions

[Tex/LaTex] How to decrease algorithm indent for package algpseudocode

Your provided example code has some mistakes. The example given in your previous question How to put an algorithm and a tikz drawing (objects of different type) side-by-side in the same float environment? had no mistakes.

I will start with a short analysis of your errors.

First of all it seems that you haven't read any documentation. Sorry for the hard words.
The argument of the environment subfigure is the width. You want to have two subfigure environments besides each other. A simple calculation shows that .5\linewidth+\quad+.5\linewidth is greater than \textwidth. (quad=\hspace{1em}). The result is an overfull hbox
You set the following combination
```
\fbox{
  \begin{environment}
```
and this results in an extra horizontal space because you didn't comment the extra space. The correct form is
```
\fbox{%
  \begin{environment}
```
You can't encapsule subfigure within a \fbox. Inside subfigure you can use the environment adjustbox to frame the algorithmic environment with the correct width calculation. (Used in the example.)
The algorithmic environment has no direct solution avoiding the indentation. In the example I redefined the environment itself by adding the length definition:
```
\labelwidth0pt\labelsep0pt %%ADDED
```
To the ifequal test. In this way you can use the optional argument of algorithmic as usual. (Thanks to Werner)

A second approach (recommened) is to use the command patchmd provided by the package etoolbox. (For more information see the documentation). Normally the command patchcmd doesn't work with optional arguments. By a suggest trick (Thanks egreg) we can use the following combination:
```
\expandafter\patchcmd\csname\string\algorithmic\endcsname%
  {\labelwidth 0.5em}{\labelwidth0pt\labelsep0pt}{}{}
```
An explanation is given in the threat How can I use \patchcmd with commands with optional arguments?

Here is the example:

\documentclass{article}
\usepackage{algorithm}% http://ctan.org/pkg/algorithm
\usepackage{algpseudocode}% http://ctan.org/pkg/algorithmicx

\usepackage{caption}
\usepackage{subcaption}
\usepackage{tikz}
\usepackage{adjustbox}
\usepackage{etoolbox}

\makeatletter
\expandafter\patchcmd\csname\string\algorithmic\endcsname%
      {\labelwidth 0.5em}{\labelwidth0pt\labelsep0pt}{}{}
%\renewenvironment{algorithmic}[1][0]%
%   {%
%   \edef\ALG@numberfreq{#1}%
%   \def\@currentlabel{\theALG@line}%
%   %
%   \setcounter{ALG@line}{0}%
%   \setcounter{ALG@rem}{0}%
%   %
%   \let\\\algbreak%
%   %
%   \expandafter\edef\csname ALG@currentblock@\theALG@nested\endcsname{0}%
%   \expandafter\let\csname ALG@currentlifetime@\theALG@nested\endcsname\relax%
%   %
%   \begin{list}%
%      {\ALG@step}%
%      {%
%      \rightmargin\z@%
%      \itemsep\z@ \itemindent\z@ \listparindent2em%
%      \partopsep\z@ \parskip\z@ \parsep\z@%
%      \labelsep 0.5em \topsep 0.2em%\skip 1.2em 
%      \ifthenelse{\equal{#1}{0}}%
%         {\labelwidth0pt\labelsep0pt}% %%ADDED / CHANGED
%         {\labelwidth 1.2em}%
%      \leftmargin\labelwidth \addtolength{\leftmargin}{\labelsep}% Ok. the perfect leftmargin :-))
%      \ALG@tlm\z@%
%      }%
%   \setcounter{ALG@nested}{0}%
%   \ALG@beginalgorithmic%
%   }%
%   {% end{algorithmic}
%   % check if all blocks are closed
%   \ALG@closeloops%
%   \expandafter\ifnum\csname ALG@currentblock@\theALG@nested\endcsname=0\relax%
%   \else%
%      \PackageError{algorithmicx}{Some blocks are not closed!!!}{}%
%   \fi%
%   \ALG@endalgorithmic%
%   \end{list}%
%   }%
\begin{document}
\section{foo}
Text

\setlength\fboxsep{0pt}
\renewcommand\algorithmicindent{.5em}

\begin{figure}[!ht]

  \begin{subfigure}[b]{.5\linewidth}
  \begin{adjustbox}{minipage=\linewidth,frame}
    \begin{algorithmic}
      \Procedure{Euclid}{$a,b$}\Comment{The g.c.d. of a and b}
        \State $r\gets a\bmod b$
        \While{$r\not=0$}\Comment{We have the answer if r is 0}
          \State $a\gets b$
          \State $b\gets r$
          \State $r\gets a\bmod b$
        \EndWhile\label{euclidendwhile}
        \State \textbf{return} $b$\Comment{The gcd is b}
      \EndProcedure
    \end{algorithmic}
   \end{adjustbox}
    \caption{Algorithm}\label{fig:alg}
  \end{subfigure}%
  \begin{subfigure}[b]{.5\linewidth}
    \centering
    \tikz\draw [fill=red!20] (0,0) rectangle (3,2);
    \caption{tikz}\label{fig:tikz}
  \end{subfigure}
  \caption{Both}\label{fig:both}
\end{figure}

Text \ref{fig:alg} and \ref{fig:tikz} and \ref{fig:both}

\end{document}

[Tex/LaTex] Indenting lines of code in algorithm

In the following example code I defined two new commands allowing you to change the indentation; simply enclose the desired fragment using \bindent, \eindent; the length \myindent controls the indent amount:

\documentclass{article}
\usepackage{algorithm,algorithmic}
\usepackage{caption}

\newlength\myindent
\setlength\myindent{2em}
\newcommand\bindent{%
  \begingroup
  \setlength{\itemindent}{\myindent}
  \addtolength{\algorithmicindent}{\myindent}
}
\newcommand\eindent{\endgroup}

\begin{document}

\begin{algorithm}[H]
\caption*{my algorithm}
\begin{algorithmic}
    \STATE \textbf{Stage one:} this is stage one
    \bindent
    \FORALL{i}
        \STATE do something
    \ENDFOR
    \eindent
    \STATE \textbf{Stage two:} this is stage two
    \bindent
    \STATE Update the trie: 
    \FORALL{j}
    \STATE do something
    \ENDFOR
    \eindent
\end{algorithmic}
\end{algorithm}

\end{document}

enter image description here

Some comments to the code:

\newlength\myindent % define a new length \myindent
\setlength\myindent{6em} % assign the length 2em to \myindet
\newcommand\bindent{%
  \begingroup % starts a group (to keep changes local)
  \setlength{\itemindent}{\myindent} % set itemindent (algorithmic internally uses a list) to the value of \mylength
  \addtolength{\algorithmicindent}{\myindent} % adds \mylength to the default indentation used by algorithmic
}
\newcommand\eindent{\endgroup} % closes a group

Best Answer

Related Solutions

[Tex/LaTex] How to decrease algorithm indent for package algpseudocode

[Tex/LaTex] Indenting lines of code in algorithm

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