Have a default pre value in a multicite

Question

I am using the biblatex package and I am trying to modify the \cites command.

The \cites command is defined as

\cites(<pre>)(<post>)[<pre>][<post>]{<key>}...[<pre>][<post>]{<key>}

I'll add some indexes to clarifiy what I'm trying to do.

\cites(<pre_0>)(<post_0>)[<pre_1>][<post_1>]{<key_1>}...[<pre_n>][<post_n>]{<key_n>}

pre_0 will be shown preceding the multicite and post_0 will be shown at the end.

I am trying to write a new command, that behaves exactly like \cites does, with the difference that pre_1 to pre_n are filled with a default value.

All I achieved until now is to use a default value for pre_0 using

\newcommand{\compares}{\cites[Cf. ]}

but I don't need to use pre_0. If it were an optional paramter to my new command, it would be nice, but it's not a must.

I was able to do this for the \cite command like this(Cf. is the default):

\newcommand{\compare}[2][]{\cite[Cf.][#1]{#2}}

Now I'd like to have the same behaviour for the \cites command. How can I achieve this?

Answer 1

I am only starting to learn how to beat on biblatex. In general, you are trying to declare a new multicite command. For the numeric style the \cites is defined by

\DeclareMultiCiteCommand{\cites}[\mkbibbrackets]{\cite}{\multicitedelim}

so we want

\DeclareMultiCiteCommand{\mycites}[\mkbibbrackets]{\mycite}{\multicitedelim}

We now need to define \mycite to do what we want. Again starting from teh original numeric style

\DeclareCiteCommand{\cite}[\mkbibbrackets]
  {\usebibmacro{prenote}}
  {\usebibmacro{citeindex}%
   \usebibmacro{cite}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

we can go to

\DeclareCiteCommand{\mycite}[\mkbibbrackets]
  {\usebibmacro{myprenote}}
  {\usebibmacro{citeindex}%
   \usebibmacro{cite}}
  {\multicitedelim}
  {\usebibmacro{mypostnote}}

leaving us to define \myprenote and \mypostnote. The originals are defined in biblatex.def as

\newbibmacro*{prenote}{%
  \iffieldundef{prenote}
    {}
    {\printfield{prenote}%
     \setunit{\prenotedelim}}}

\newbibmacro*{postnote}{%
  \iffieldundef{postnote}
    {}
    {\setunit{\postnotedelim}%
     \printfield{postnote}}}

This is where I am not exactly sure what is best. One solution is

\newbibmacro*{myprenote}{x\space}
\newbibmacro*{mypostnote}{, y}

where x and y are whatever you want them to be. I don't think this is really the bibltex way and I think slightly better is

\newbibmacro*{myprenote}{\printtext{x}\setunit{\prenotedelim}}
\newbibmacro*{mypostnote}{\printtext{\addcomma\space y}\setunit{\postnotedelim}}

but I don't really understand what this is doing and I think we should be using field formatting. Putting it all together

\documentclass{article}
\usepackage{biblatex}
\addbibresource{biblatex-examples.bib}
\newbibmacro*{myprenote}{\printtext[prenote]{x}\setunit{\prenotedelim}}
\newbibmacro*{mypostnote}{\printtext[postnote]{\addcomma\space y}\setunit{\postnotedelim}}
\DeclareCiteCommand{\mycite}[\mkbibbrackets]
  {\usebibmacro{myprenote}}
  {\usebibmacro{citeindex}%
   \usebibmacro{cite}}
  {\multicitedelim}
  {\usebibmacro{mypostnote}}
\DeclareMultiCiteCommand{\mycites}[\mkbibbrackets]{\mycite}{\multicitedelim}

\begin{document}
\cites(a)(b)[x][y]{angenendt}[x][y]{bertram}

\mycites(a)(b){angenendt}{bertram}
\end{document}

Answer 2

The \AtNextCite hook allows you to easily define variants of existing citation commands.

\newrobustcmd*{\mycite}{\AtNextCite{<code>}\cite}

In <code> you can modify biblatex counters, generic commands, bibliography macros or formatting directives. These changes are applied only to the following \cite. Citation argument parsing can be left to biblatex. A mulitcite variant of \mycite can be defined similarly:

\newrobustcmd*{\mycites}{\AtNextCite{<code>}\cites}

Here's an example addressing your question. In the new citation commands you can override the default prenote \bibstring{confer} by providing a non-empty prenote argument.

\documentclass{article}
\usepackage[style=verbose,maxnames=1]{biblatex}

\newrobustcmd*{\cfautocite}{\cfcitehook\autocite}
\newrobustcmd*{\Cftextcite}{\cfcitehook\Textcite}
\newrobustcmd*{\cfautocites}{\cfcitehook\autocites}
\newrobustcmd*{\Cftextcites}{\cfcitehook\Textcites}

\newrobustcmd*{\cfcitehook}{%
  \AtNextCite{\renewbibmacro*{prenote}{\usebibmacro{prenote:confer}}}}

\newbibmacro*{prenote:confer}{%
  \iffieldundef{prenote}
    {\bibstring{confer}}
    {\printfield{prenote}}%
  \setunit{\prenotedelim}}

\newcommand{\cmd}[1]{\texttt{\textbackslash #1}}
\addbibresource{biblatex-examples.bib}

\begin{document}
\null\vfill\noindent
\cmd{Textcite}: \Textcite[e.g.][10]{companion} showed that... \\
\cmd{autocite}: Filler text \autocite[10]{companion,knuth:ct:a}. \\
\cmd{Textcites}: \Textcites[10]{companion}[e.g.][]{knuth:ct:a}{glashow} showed that... \\
\cmd{autocites}: Filler text \autocites[10]{companion}[e.g.][]{knuth:ct:a}{glashow}. \\\\
\cmd{Cfextcite}: \Cftextcite[e.g.][10]{companion} showed that... \\
\cmd{cfautocite}: Filler text \cfautocite[10]{companion,knuth:ct:a}. \\
\cmd{Cftextcites}: \Cftextcites[10]{companion}[e.g.][]{knuth:ct:a}{glashow} showed that...\\
\cmd{cfautocites}: Filler text \cfautocites[10]{companion}[e.g.][]{knuth:ct:a}{glashow}.
\end{document}

The same approach works for multiprenote - a field that can't be accessed via \DeclareCiteCommand or \DeclareMultiCiteCommand.

\newrobustcmd*{\cfmulticitehook}{%
  \AtNextCite{\renewbibmacro*{multiprenote}{\usebibmacro{multiprenote:confer}}}}

\renewbibmacro*{multiprenote:confer}{%
  \iffieldundef{multiprenote}
    {\bibstring{confer}}
    {\printfield{multiprenote}}%
  \setunit{\prenotedelim}}