Cfrgtkky

In a pseudocode, I would like to assign varnothing to a variable.

My code goes like this:

documentclass[runningheads]{llncs} 

usepackage{graphicx} 

usepackage{algpseudocode} 

usepackage{algorithm}

usepackage{amsmath}

begin{document}

begin{algorithm} 

caption{Find...} 

begin{algorithmic}[1] State $RS$ $leftarrow$ $varnothing$ end{algorithmic} 

end{algorithm} 

end{document}

Unfortunately this doesn't work. The error message I got is the following:

State $RS$ $leftarrow varnothing $ The control sequence at the end

of the top line of your error message was never def'ed. If you have

misspelled it (e.g., `hobx'), type `I' and the correct spelling

(e.g., `Ihbox'). Otherwise just continue, and I'll forget about

whatever was undefined. ! Undefined control sequence. 

varnothing l.103 ...quad quad $R$ $leftarrow$ $varnothing $

Comment{$R$ is the set ... The control sequence at the end of the top

line of your error message was never def'ed. If you have misspelled

it (e.g., `hobx'), type `I' and the correct spelling (e.g.,

`Ihbox'). Otherwise just continue, and I'll forget about whatever was

undefined.

Do you have any ides on how this can be resolved?

FYI, I've already installed amsmath from texlive-latex-base in debian 9.

Thanks,

Pavlos

varnothing belongs to the set of symbols in the package amssymb. So include it in your preamble as usepackage{amssymb} and you are good to go.

documentclass{article} 

usepackage{graphicx} 

usepackage{algpseudocode} 

usepackage{algorithm}

usepackage{amsmath}

usepackage{amssymb}

begin{document}

    begin{algorithm} 

        caption{Find...} 

        begin{algorithmic}[1] State $RS$ $leftarrow$ $varnothing$ end{algorithmic} 

    end{algorithm} 

end{document}

with which you will get: