LaTeX: Avoid new paragraph?

Question

I use the \todo command from the \todonotes package. I'd like to layout my source to put \todos separately from the previous paragraph:

Some text.

\todo{make note}

But I don't want \todo to start a new paragraph, or it screws up the spacing of the document.

Is there a command to avoid this?

If there were a command/package to consume the whitespace up to it, then I could redefine \todo to use it.

Edit: Adding a % between everything is obviously very irritating. Anything else?

Answer 1

I have to agree with everybody else that you should probably just add the %, but I do find this question interesting. The problem is that as soon as LaTeX reads the empty line, it gets converted into the \par command, which ends the previous paragraph. At the beginning of \todo, that \par command has already been executed, and it's impossible to undo it (I think). So your only hope is to keep that \par from being inserted or from behaving like it normally does. If you want to prevent it from being inserted, you could try reading Chapter 8 of "The TeXbook", which should tell you how an empty line is converted to \par. Alternatively, you could try to make a solution based on the following kind of idea:

Some text.{\let\par\relax

\todo{make note}}

But watch out! You definitely don't want to globally change the behavior of \par, which is why I added an extra pair of curly braces (LaTeX commands are scoped, so the new definition of \par only takes effect within the group where the definition was made). Good luck.

Answer 2

When the macro precedes the unwanted space, the % is not necessary if you make use of \@ifnextchar and \@gobble.

Consider something like (in the preamble, of course):

\makeatletter
\let\oldtodo\todo
\renewcommand\todo[1]{%
\oldtodo{#1}%
\@ifnextchar\par{\@gobble}{}}
\makeatother

That way, if you have something like:

\todo{Stuff}

Things

it will act the same as

\todo{Stuff}
%
Things

or

\todo{Stuff}
Things

You can generalize such things with a macro like

\makeatletter
\newcommand\gobblepars{%
    \@ifnextchar\par%
        {\expandafter\gobblepars\@gobble}%
        {}}
\makeatother

You can then use \gobblepars wherever you want to eat space (like after the todo). You can also re-define todo (as shown above) to automatically place a \gobblepars after it.

To handle the leading empty space. you can use \gobblepars too, but you have to be explicit. For example:

Some text\gobblepars

\todo{Stuff}

will prevent a \par from showing up between the two lines.