Illegal parameter number in definition of \test and other errors in Beamer Poster

Question

I need help troubleshooting errors in my Beamer Poster (accessible on Overleaf). Most of the errors are of the following forms:

Illegal parameter number in definition of \test.
Illegal parameter number in definition of \iterate.
Illegal parameter number in definition of \beamer@doifinframe.

Oddly the code compiles and produces the desired output, but I can't get rid of these errors. My code was adapted from this poster, which doesn't have said errors. I have tried looking at the deltas between the two posters to find the source of the errors with no success.

Answer 1

When TeX complains about an "Illegal parameter number in definition", it has just read a macro parameter character # that either isn't followed by 1, 2, ... 9, or the used number is outside of the parameter range of the current definiton. (In your document this definition is hidden somwhere in the block environment.)

As you are trying to typeset a literal # character in this case, e.g. in #zhu, just escape it as \#.

Answer 2

If you came here looking for a potential cause to the error message ! Illegal parameter number in definition of \iterate and you are using beamer and knitr, then chances are that you forgot to declare the relevant frame as [fragile].

Simply replace \frame or \begin{frame} by \frame[fragile] or \begin{frame}[fragile] respectively.