Post-process markdown code to paste into Wordpress

postprocess_markdown.R

change_tex_delimiters <- function(x) 
{
  # replace latex equation delimiters ($$) if present
  eq <- which(x == "$$")   # find positions of equations
  if (length(eq) > 0) {
    eq.begin <- eq[c(T,F)]    
    eq.end <- eq[c(F,T)]
    for (i in eq.begin)
      x[[i]] <- "$latex \\displaystyle"
    for (i in eq.end)
      x[[i]] <- "$"
  }
  
  # replace inline latex $ delimiters
  ptn <- "\\$(.*?)\\$"              # find non-greedy between delimiters
  replacement <- "$latex \\1$"      # \\1 = back-reference
  str_replace_all(x, ptn, replacement)
}


change_backticks_to_italics <- function(x)
{
  # change backticks (`) to simple italics (*)
  ptn <- "`([^\\`]+?)`"           # do not replace ```r or ```
  replacement <- "\\*\\1\\*"      # \\1 = back-reference
  str_replace_all(x, ptn, replacement)
}


md_for_wp <- function(f, f.out=NULL)
{
  x <- readLines(f)
  xn <- change_tex_delimiters(x)
  xn <- change_backticks_to_italics(xn)
  if (is.null(f.out))
    f.out <- str_replace(f, "\\.md$", "-wp.md")
  writeLines(xn, f.out)  
}