I want \newcommand to replace something in a document by something else

Question

I want to define \newcommand{\B} in 2 different ways and switch between them in the simplest way – just using a comment mark, %. Let's look at the example:

\documentclass[a4paper,9pt]{article}
\usepackage[utf8]{inputenc}

% My 1st definition 
\newcommand{\B}[1]{\textbf{#1}}
% My 2nd definition (it’s wrong that’s way I’m asing)
\newcommand{\B}{$\ldots$}

\begin{document}
Let \B{1.345} be 

\end{document}

Using first definition the value 1.345 is bolded. If I use second definition I should always get only $\ldots$ so value 1.345 should be removed. I tried to add spaces (crude solution) but value skipped line below. Any suggestion?

Answer 1

You need to “gobble” the argument {1.345} in the \ldots case. (Specify \B with one argument but do not use #1.)

Reference for “gobbling”

• Why does \@gobble take one argument

Code

\documentclass[a4paper,9pt]{article}
\usepackage[utf8]{inputenc}

% My 1st definition 
% \newcommand{\B}[1]{\textbf{#1}}
% My 2nd definition
\newcommand{\B}[1]{$\ldots$}% (do’nt use #1 here but specify [1])

\begin{document}
Let \B{1.345} be 

\end{document}

Output

Let … be