How to make footnotes span multiple columns?

Question

I am preparing a scientific paper for IEEE using the IEEEtran style that gives a two column layout. However, URLs are not references and should be put in footnotes. Some of my URLs are long, too long to fit into one column, but short enough to make a single line across both columns. I know how to put floats and long tables and equations spanning both columns, but I have not been able to find any way to make the footnote span both columns. Any ideas?

The bigfoot package may be able to do this, but the documentation mainly reference the manyfoot package, which seems not able to do this. The ftnright package is not a solutions since it puts all footnotes in the right hand column. There are two related questions about the same issue in the ACM format and for the memoir document class, but both are largely unanswered, hence this post.

A code fragment illustrating the problem

\documentclass[10pt,conference,a4paper,twocolumn]{IEEEtran}
\usepackage[colorlinks,urlcolor=blue]{hyperref}
\begin{document}
Some random text\footnote{\url{
http://ec.europa.eu/digital-agenda/interoperability-standardisation-connecting-ehealth-services}}
\end{document}

Answer 1

The big problem with your idea is the way, LaTeX is building the page.

If you have two colums on the page, LaTeX has to calculate it. You want to end the "two column mode", change to one column to add your footnote or footnotes. There are a lot of things influencing the result, like the length of the paragraphs, the length of the footnotes, that causes an changing of the length of the column etc. That is not easy to calculate!

If you argue but there is the possibilty to have an abstract in one column please see that the situation is an other there. It is much more easier to insert an box for the complete textwidth at the beginning than at the end.

My english is not so good, so please have a look for example to this question and see the accepted answer. perhaps it is today possible, to do the recalculation with expl3 as mentiond by Frank Mittelbach, but I can't do that.

So I suggest you to use the following MWE to get hyphenated urls placed in the column they belong to:

\documentclass[10pt,conference,a4paper,twocolumn]{IEEEtran}

\usepackage{showframe} % <======================== shows the typing area
\usepackage{blindtext} % <========================= to create blind text
\usepackage[hyphens]{url} % <================ allows hyphenating of urls

\usepackage[colorlinks,urlcolor=blue]{hyperref}


\begin{document}
\Blindtext
Some random text\footnote{\url{
http://ec.europa.eu/digital-agenda/interoperability-standardisation-connecting-ehealth-services}}
\Blindtext
Some random text\footnote{\url{
http://ec.europa.eu/digital-agenda/interoperability-standardisation-connecting-ehealth-services}}
\Blindtext
\end{document}

and the resulting first page:

showing clickable blue urls.

Answer 2

In my case the problem was not "getting the footnote to span two columns" -- it was quite willing to do that without any help from me.

its own API, so rengas can also be generated on demand.\footnote{{\tt
curl --data
"ws\_token=6B6JHXiKUAJ9VXTBymeGMWgvvpQMZ8uU\&cid=214\&t1=great\&t2=snakes"
http://ccg.doc.gold.ac.uk/research/flowr/flowrweb/}}

(NB. Long footnotes are not necessarily URLs.)

But of course this looks horrible. Hence, the following hack, which solves the problem:

Regarding beauty: Modelling the complexity and
\newpage
\noindent
coherence of a poem could be a large task, but one simple method would
be to use the pairwise word similarity of words in the poem as a
proxy.

Resulting in new output:

Answer 3

This might help you. You are required not to use the \url environment. If you are not using it, then it span across single column. The screenshot of the output has been attached here with.

\documentclass[10pt,conference,a4paper,twocolumn]{IEEEtran}
\usepackage[colorlinks,urlcolor=blue]{hyperref}
\begin{document}
Some random text\footnote{http://ec.europa.eu/digital-agenda/interoperability-standardisation-connecting-ehealth-services}
\end{document}