I have a problem. The following code runs

 X \ar[d] \ar[r] & Y \ar[d]\\
 T                 & S\\} \]

Even the following runs

 X \ar[r] & Y \ar[d]\\
         & S\\} \]

But not this:

 X \ar[dr] \ar[r] & Y \ar[d]\\
                  & S\\} \]

My code is:


X   \ar[dr] \ar[r] & Y \ar[d]\\
             & S\\} \]
  • I have Windows 10. I use Overleaf.
    – Grobber
    Aug 6, 2017 at 5:44
  • It seems there is a problem with my macros. I am trying to narrow it down.
    – Grobber
    Aug 6, 2017 at 6:11
  • Oh my! I had redefined \char to say char. This seems similar to some other earlier post. Could you please tell me the reason for such mishap?
    – Grobber
    Aug 6, 2017 at 6:19
  • Could you please tell me why \renewcommand{\char}{char} causes the problem?
    – Grobber
    Aug 6, 2017 at 6:31
  • I have added my error-prone code above.
    – Grobber
    Aug 6, 2017 at 6:39

1 Answer 1


\char is a TeX primitive. Redefining it is bound to break almost every LaTeX document.

This is like redefining \box or \fi or \uppercase (I remember of a class which did the latter).

Never do \renewcommand if you never heard about the command you'd like to redefine.

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