Include a line break in algorithmic while maintaining indentation

Question

I have this code:

\DeclareCaptionFormat{algor}{%
  \hrulefill\par\offinterlineskip\vskip1pt%
    \textbf{#1#2}#3\offinterlineskip\hrulefill}
\DeclareCaptionStyle{algori}{singlelinecheck=off,format=algor,labelsep=space}
\captionsetup[algorithm]{style=algori}

\begin{document}
    \section{Struttura dati}
    \begin{floatleft}
        \captionof{algorithm}{Leggi file .gpx}\label{getgpx}
        \begin{algorithmic}[1]
                  \State $speed \gets computeSpeed(\linebreak gpx.track(i).segment(j).delta\_s(q), \linebreak gpx.track(i).segment(j).delta\_t(q));$
            \end{algorithmic}
    \end{floatleft}
\end{document}

This is how code is shown:

I want the lines gpx.track....delta_s(q),, gpx.track....delta_t(q), and ); to be indented exactly as the beginning of line 27 is. I've tried using the \indent command but the indentation space is not the same as in the rest of the document and the final result is chaotic.

Answer 1

The default indent for each block in the algorithmic environment (from the algorithmicx package) is \algorithmicindent. As such, you can place the entire line of code in a top-aligned \parbox[t] of adequate width or use the varwidth environment from the varwidth package, and indent as needed:

\documentclass{article}
\usepackage{algorithm}% http://ctan.org/pkg/algorithm
\usepackage{algpseudocode}% http://ctan.org/pkg/algorithmicx
\usepackage{varwidth}% http://ctan.org/pkg/varwidth
\begin{document}
\section{Struttura dati}
\begin{algorithm}
  \caption{Leggi file .gpx}\label{getgpx}
  \begin{algorithmic}[1]
    \State \begin{varwidth}[t]{\linewidth}
      speed~$\gets$~computeSpeed(\par
        \hskip\algorithmicindent gpx.track(i).segment(j).delta\_s(q),\par
        \hskip\algorithmicindent gpx.track(i).segment(j).delta\_t(q));
      \end{varwidth}
  \end{algorithmic}
\end{algorithm}
\end{document}​

Here is another alternative that could be used instead. It utilized the a modified version of \Statex, also supplied by algorithmicx. It now takes an optional argument indicating the number of indents to apply to the specific line, without numbering it (default for \Statex).

\documentclass{article}
\usepackage{algorithm}% http://ctan.org/pkg/algorithm
\usepackage{algpseudocode}% http://ctan.org/pkg/algorithmicx
\makeatletter
\let\OldStatex\Statex
\renewcommand{\Statex}[1][3]{%
  \setlength\@tempdima{\algorithmicindent}%
  \OldStatex\hskip\dimexpr#1\@tempdima\relax}
\makeatother
\begin{document}
\section{Struttura dati}
\begin{algorithm}
  \caption{Leggi file .gpx}\label{getgpx}
  \begin{algorithmic}[1]
    \State speed~$\gets$~computeSpeed(
    \Statex gpx.track(i).segment(j).delta\_s(q),
    \Statex[2] gpx.track(i).segment(j).delta\_t(q));
  \end{algorithmic}
\end{algorithm}
\end{document}

---

Note that I've stripped the unnecessary preamble content from the minimal working example (MWE) posted above. This is encouraged when posting problems/question - something that can compile that reproduces the problem.

Answer 2

If all the other solutions seem too complicated, try using a combination of \newline with \hspace*{}:

\documentclass{article}
\usepackage{algorithm}
\usepackage{algpseudocode}

\begin{document}
\section{Struttura dati}

\begin{algorithm}
  \caption{Leggi file .gpx}\label{getgpx}
  \begin{algorithmic}[1]
    \State speed~$\gets$~computeSpeed(\newline
        \hspace*{5em} gpx.track(i).segment(j).delta\_s(q), \newline
        \hspace*{5em} gpx.track(i).segment(j).delta\_t(q));
  \end{algorithmic}
\end{algorithm}

\end{document}

This produces

Answer 3

This is an addition to Werner's answer. As noted in the comments, that solution does not work with \For and \While loops since they include a "do" at the end. One can define alternative versions of \For and \While as in the example below

\documentclass{article}
\usepackage{algorithm,algpseudocode}
\makeatletter
\newcommand{\StatexIndent}[1][3]{%
  \setlength\@tempdima{\algorithmicindent}%
  \Statex\hskip\dimexpr#1\@tempdima\relax}
\algdef{S}[WHILE]{WhileNoDo}[1]{\algorithmicwhile\ #1}%
\makeatother
\begin{document}
\begin{algorithm}[H]
  \caption{Cool algorithm}
  \begin{algorithmic}[1]
    \WhileNoDo{everything is all right, and}
    \StatexIndent[2] the sun is shining bright \algorithmicdo
       \State Sing and dance
    \EndWhile
  \end{algorithmic}
\end{algorithm}
\end{document}

I hope it is helpful to someone else too.

Answer 4

I had the same issue with the If block. For me, it turned out, that using \phantom was the solution. Just insert letters and characters until the indent and the wrapping is OK. Then put \phantom before these artificial letters.

\documentclass{article}
\usepackage{algpseudocode}

\begin{document}

\begin{algorithmic}[1]
\Procedure{Demo}{}
\If{This is a very long condition with a long natural text $\mathsf{but\ math\ can\ be\ used,\ too}$ \phantom a \phantom . \phantom . \phantom . and the indent should be right}
\State Statement
\EndIf
\EndProcedure
\end{algorithmic}

\end{document}

Answer 5

I had a similar problem, except that my long expression was the condition of an If statement. I fixed it by using a LaTeX array environment for my expression, the output looks a little strange because it does not look like idomatic pesudocode.

\If{$\left(
    \begin{array}{l}
    (current\_context \neq \text{NULL})\, \vee \\
    (MR\_num\_outstanding\_contexts < MR\_max\_contexts) \\
    \end{array}
    \right)$}

If the math-style output is acceptable then this is pretty easy.