Previous: \protect, Up: Definitions [Contents][Index]
\ignorespaces & \ignorespacesafterend
Synopsis:
\ignorespaces
or
\ignorespacesafterend
Both commands cause LaTeX to ignore spaces after the end of the command up until the first non-space character. The first is a command from Plain TeX, and the second is LaTeX-specific.
The ignorespaces
is often used when defining commands via
\newcommand
, or \newenvironment
, or \def
. The
example below illustrates. It allows a user to show the points values
for quiz questions in the margin but it is inconvenient because, as
shown in the enumerate
list, users must not put any space between
the command and the question text.
\newcommand{\points}[1]{\makebox[0pt]{\makebox[10em][l]{#1~pts}} \begin{enumerate} \item\points{10}no extra space output here \item\points{15} extra space between the number and the `extra' \end{enumerate}
The solution is to change to this.
\newcommand{\points}[1]{% \makebox[0pt]{\makebox[10em][l]{#1~pts}}\ignorespaces}
A second example shows spaces being removed from the front of text. The
commands below allow a user to uniformly attach a title to names. But,
as given, if a title accidentally starts with a space then
\fullname
will reproduce that.
\makeatletter \newcommand{\honorific}[1]{\def\@honorific{#1}} % remember title \newcommand{\fullname}[1]{\@honorific~#1} % put title before name \makeatother \begin{tabular}{|l|} \honorific{Mr/Ms} \fullname{Jones} \\ % no extra space here \honorific{ Mr/Ms} \fullname{Jones} % extra space before title \end{tabular}
To fix this, change to
\newcommand{\fullname}[1]{\ignorespaces\@honorific~#1}
.
The \ignorespaces
is also often used in a \newenvironment
at the end of the begin clause, that is, as part of the second
argument, as in \begin{newenvironment}{env
name}{... \ignorespaces}{...}
.
To strip spaces off the end of an environment use
\ignorespacesafterend
. An example is that this will show a much
larger vertical space between the first and second environments than
between the second and third.
\newenvironment{eq}{\begin{equation}}{\end{equation}} \begin{eq} e=mc^2 \end{eq} \begin{equation} F=ma \end{equation} \begin{equation} E=IR \end{equation}
Putting a comment character %
immediately after the
\end{eq}
will make the vertical space disappear, but that is
inconvenient. The solution is to change to
\newenvironment{eq}{\begin{equation}}{\end{equation}\ignorespacesafterend}
.