Collection of knitr Hooks

ext-env.tex

% Full Screen Environment for Beamer Slides
\newenvironment{changemargin}[2]{%
\begin{list}{}{%
  \setlength{\topsep}{0pt}%
  \setlength{\leftmargin}{#1}%
  \setlength{\rightmargin}{#2}%
  \setlength{\listparindent}{\parindent}%
  \setlength{\itemindent}{\parindent}%
  \setlength{\parsep}{\parskip}%
}%
\item[]}{\end{list}}

ext-hooks.R

# Wraps chunk in a fragile frame environment for beamer
fragile = function(before, options, envir){
  if (before) {
    return('\\begin{frame}[fragile]\n')
  } else {
    return('\\end{frame}')
  }
}

# Wraps figures inside a full figure environment for beamer
fullfig = function(before, options, envir) {
  if (before) {
    return('\\begin{changemargin}{-1cm}{-1cm}\n')
  } else {
    return('\n\\end{changemargin}')
  } 
}

wrap-env.R

# Higher Order Functions for Latex Hooks

wrap_in_env <- function(begin, end = begin){
  function(x, options){
    str_c("\n\\begin{", begin, "}\n", x, "\n\\end{", end, "}")
  }
}

# Example Usage
frame_hook <- wrap_in_env('frame')

So instead of print(x), I could just do return(x) ? Is there any advantage to doing it this way?

yes you can return(x); in this case, print(x) is equivalent to return(print(x)) and the function both prints x and returns x, because print(x) returns x

in short, print(x) brings the side effect of printing, which is not necessary here

Got it. Makes sense. I have updated the gist based on your comment.