[Tex/LaTex] Comment on the same line as \If in algorithm introduces a vertical whitespace

algorithm2ealgorithmscomments

I am using the algorithm2e package to write a pseudo code algorithm. I would like to add a comment with \tcp, on the same line as an \If statement. I managed to do so by putting the \tcp command between parenthesis right after the \If, but it introduces a vertical space between the If and the following line.

\usepackage[titlenumbered,ruled,noend,algo2e]{algorithm2e}
\usepackage{algorithm}

\begin{document}
    \begin{algorithm}[t]
        \If(\tcp*[l]{comment}){$k = K$}{do stuff}
        \If{$k \neq K$}{do other stuff}
    \end{algorithm}
\end{document}

Results in:

Anyone knows how to fix that?

Best Answer

You should use the [h] specification of \tcp*, as explained here at page 32.

\documentclass{article}
\usepackage[titlenumbered,ruled,noend,algo2e]{algorithm2e}
\usepackage{algorithm}

\begin{document}
    \begin{algorithm}[t]
        \If(\tcp*[h]{comment}){$k = K$}{do stuff}
        \If{$k \neq K$}{do other stuff}
    \end{algorithm}
\end{document}

Explanation

To match your first two requests, I've redefined the behavior of for to have an end statement by adding the lines:

\algdef{SE}{For}{End}[2]{%
  \textkeyword{for} \(#1\) \textkeyword{to} \(#2\) \textkeyword{do begin}}{%
  \textkeyword{end}}

To match your last request, it suffices to add the line:
```
\algrenewcommand\textkeyword{\textrm}
```
which redefines the font for keywords to be \textrm instead of \textbf.
In regards of your 3rd request, there are two ways.
- If you want the algorithm to behave as an algorithm, simply load the algorithm package with the option plain as in the above MWE:
```
\usepackage[plain]{algorithm}
```
- If you want the algorithm to behave as a figure, there is no need to load the algorithm package, simply insert the algorithmic environment inside a figure, i.e. replace the lines
```
\begin{algorithm}
\begin{algorithmic}[1]
...
\end{algorithmic}
\caption{Paull's algorithm}
\end{algorithm}
```
  with
```
\begin{figure}
\begin{algorithmic}[1]
...
\end{algorithmic}
\caption{Paull's algorithm}
\end{figure}
```
  and you will have

Addendum

This is the complete implementation of the algorithm in the figure:

\documentclass{article}
\usepackage[plain]{algorithm}
\usepackage{algpascal}

\begin{document}

\algrenewcommand\textkeyword{\textrm}
\algdef{SE}{For}{End}[2]{%
  \textkeyword{for} \(#1\) \textkeyword{to} \(#2\) \textkeyword{do begin}}{%
  \textkeyword{end}}
\algdef{SE}{ForEach}{End}[1]{%
  \textkeyword{for each} #1 \textkeyword{do begin}}{%
  \textkeyword{end}}

\begin{algorithm}
\begin{algorithmic}[1]
\State Assign an ordering $A_{1}, \dots, A_{n}$ to the nonterminals of the grammar.
\For{i := 1}{n}
    \For{j := 1}{i-1}
        \ForEach{production of the form $A_{i} \rightarrow A_{j} \alpha$}
            \State remove $A_{i} \rightarrow A_{j} \alpha$ from the grammar
            \ForEach{production of the form $A_{j} \rightarrow \beta$}
                \State add $A_{i} \rightarrow \beta\alpha$ to the grammar
            \End
        \End
    \End
    \State transform the $A_{i}$-productions to eliminate direct left recursion
\End
\end{algorithmic}
\caption{Paull's algorithm}
\end{algorithm}

\end{document}

enter image description here

There is the need to define a new command \ForEach:

\algdef{SE}{ForEach}{End}[1]{%
  \textkeyword{for each} #1 \textkeyword{do begin}}{%
  \textkeyword{end}}

Note that I've defined \ForEach so to take one "text" argument, because it seemed to me the best way to define it.

If you want it to take a "math" argument, then define it as

\algdef{SE}{ForEach}{End}[1]{%
  \textkeyword{for each} \(#1\) \textkeyword{do begin}}{%
  \textkeyword{end}}

and use it as follows (amsmath is needed for the command \text):

\ForEach{\text{production of the form }A_{i} \rightarrow A_{j} \alpha}

[Tex/LaTex] Customizing some aspect of algorithmic environment

To restart line numbering from 1, you have to reset the counter ALG@line, so we define a new command \resetline to be issued when you want that change:

\makeatletter
\newcommand{\resetline}{\setcounter{ALG@line}{0}}
\makeatother

In regards of the spacing between two functions, you can use a normal skip instead of issuing a \Statex (\smallskip, \medskip, \bigskip).

MWE

\documentclass{article}
\usepackage{algorithm}
\usepackage[noend]{algpseudocode}

\makeatletter
\newcommand{\resetline}{\setcounter{ALG@line}{0}}
\makeatother

\begin{document}

\begin{algorithm}[H]
    \caption{Calcola il grado di ogni vertice del grafo $G = (V,E)$}
    \label{degree}
    \begin{algorithmic}[1]
        \Function{\textsc{Map}$( \left \langle u;v \right \rangle )$}{}
            \State \textbf{emit} $\left \langle u;v \right \rangle$
        \EndFunction
        \medskip\resetline
        \Function{\textsc{Reduce}$( \left \langle u;\Gamma(u) \right \rangle )$}{}
            \State $d(u) \gets 0$
            \ForAll{$v \in \Gamma(u)$}
                \State $d(u) \gets d(u) + 1$
            \EndFor
            \State \textbf{emit} $\left \langle u;d(u) \right \rangle$
        \EndFunction
    \end{algorithmic}
\end{algorithm}

\end{document}

Output:

enter image description here

The little gap related to the noend option is to indicate the end of the function, so I'll leave it as is, but if you really want to remove it, you can add these lines in your preamble (require the etoolbox package):

\patchcmd{\ALG@doentity}
  {\item[]\nointerlineskip}
  {\relax}
  {}
  {}

Complete code:

\documentclass{article}
\usepackage{algorithm}
\usepackage[noend]{algpseudocode}
\usepackage{etoolbox}

\makeatletter
\newcommand{\resetline}{\setcounter{ALG@line}{0}}
\patchcmd{\ALG@doentity}
  {\item[]\nointerlineskip}
  {\relax}
  {}
  {}
\makeatother

\begin{document}

\begin{algorithm}[H]
    \caption{Calcola il grado di ogni vertice del grafo $G = (V,E)$}
    \label{degree}
    \begin{algorithmic}[1]
        \Function{\textsc{Map}$( \left \langle u;v \right \rangle )$}{}
            \State \textbf{emit} $\left \langle u;v \right \rangle$
        \EndFunction
        \medskip\resetline
        \Function{\textsc{Reduce}$( \left \langle u;\Gamma(u) \right \rangle )$}{}
            \State $d(u) \gets 0$
            \ForAll{$v \in \Gamma(u)$}
                \State $d(u) \gets d(u) + 1$
            \EndFor
            \State \textbf{emit} $\left \langle u;d(u) \right \rangle$
        \EndFunction
    \end{algorithmic}
\end{algorithm}

\end{document}

Output:

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] Algorithm as figure and without italic and bold formatting

Explanation

Addendum

[Tex/LaTex] Customizing some aspect of algorithmic environment

Related Question