Spaces added to occurrences of "{}" in the TeX code

Question

Can anyone explain how to get rid of spaces that are automatically added around arguments provided in curly braces in the main part of a text? Here's a minimal example:

\documentclass{article}
\usepackage[normalem]{ulem}

\newcommand{\oldtext}[1]{}
% \newcommand{\oldtext}[1]{\sout{#1}}

\begin{document}
There is absolute no doubt {} {} {} {} that the difference between $x=3$ and $x=4$ shall 
not be ignored. After all, $3$ and $4$ are different numbers. 
So why in the world would \oldtext{anybody} \oldtext{somebody} anyone argue for that?

\end{document}

The result is:

As it can be seen, the repeated occurrences of "{}" add spaces. The "\oldtext" macro shows why this can be problematic in practice. It is used here to denote old text for which it should be possible to be made visible when needed later (by exchanging the definition of the oldtext macro). Of course, the last line of the main part of the text could be written as:

So why in the world would\oldtext{anybody}\oldtext{somebody} anyone argue for that?

but this is hard to read in the code, confuses the version control software, and would require to add a space inside the macro oldtext to avoid the old texts being stitched together, which is kind-of-ugly. Also, spaces before or after \oldtext can easily be overlooked during proof-reading of a document.

Ideally, I would like to replace the command "\newcommand{\oldtext}[1]{}" by some expression that behaves like "\relax" rather than "{\relax}".

Answer 1

Another general answer that solves the problem:

\makeatletter
\newcommand{\oldtext}[1]{\@bsphack\@esphack}
\makeatother

while \ignorespaces always eats up all the spaces \@bsphack\@esphack check if a space is needed in some cases: when there is a space after the command but not before

hi\oldtext{bla} there.

In this case the \ignorespaces solution would give

hithere.

while the \@bsphack one would correctly insert the space between the two words:

hi there.

This is the solution used by LaTeX's macros that do not typeset stuff like \label.

Answer 2

Use \ignorespaces inside of the empty {} pair. The difference between using and not using it is shown by the two macros \oldtext and \evenoldertext

\documentclass{article}

\usepackage[normalem]{ulem}


\newcommand{\oldtext}[1]{\ignorespaces}

\newcommand{\evenoldertext}[1]{}


% \newcommand{\oldtext}[1]{\sout{#1}}

\begin{document}
There is absolute no doubt {} {} {} {} that the difference between $x=3$ and $x=4$ shall 
not be ignored. After all, $3$ and $4$ are different numbers. 
So why in the world would \oldtext{anybody} \oldtext{somebody} anyone \evenoldertext{Hello} argue for that?

\end{document}