Why is there extra space prefixing the first case

Question

I don't understand why there is extra space before the mod in this formula. How can I force the m and the 0 to be aligned vertically?

Here is the LaTeX code I'm using.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}
  f(x)&=\begin{cases}
  \mod(x  , 3) &\text{; if } x \neq 0\
  0&\text{; if } x = 0
  \end{cases}
\end{align}
\end{document}

Here's a link to a similar question with the suggested \bmod macro in comments. — Celdor, Oct 19 '22 at 09:59
As Celdor mentions there are several constructions for mod, the one you're using here always assumes it comes after something, which is not the case here. — daleif, Oct 19 '22 at 10:16
Why you don't use \text{mod}? I think it's useful in this case. — manh3, Oct 19 '22 at 13:26

score 2 · Answer 1 · answered Oct 19 '22 at 12:07

For such usage you want to do

\DeclareMathOperator{\opmod}{mod}% mod as operator

Full example:

\documentclass{article}
\usepackage{amsmath}
\DeclareMathOperator{\opmod}{mod}% mod as operator
\begin{document}
\begin{align}
  f(x)&=\begin{cases}
  \opmod(x, 3) &\text{; if } x \neq 0\
  0            &\text{; if } x = 0
  \end{cases}
\end{align}
\end{document}

I'd remove the semicolons.

Why not \bmod? Compare the result of

6\bmod(x,3)

with

6\opmod(x,3)

score 1 · Answer 2 · edited Oct 22 '22 at 18:41

1

Using \bmod does the trick. as pointed out by daleif, \mod assumes there is space before it.

edited Oct 22 '22 at 18:41

Sebastiano

54,118

answered Oct 19 '22 at 11:59

Jim Newton

479

Why is there extra space prefixing the first case

2 Answers2