21.4 Named Components

li("What is the ", b("derivative"),  "of $f(x) = 1 + 2\cos(3\pi x + 4)$?")

• aiming to classify li and b as named components

dots_partition <- function(...) {
  dots <- list2(...)
  
 if (is.null(names(dots))) {
  is_named <- rep(FALSE, length(dots))
} else {
  is_named <- names(dots) != ""
}
  
  list(
    named = dots[is_named],
    unnamed = dots[!is_named]
  )
}

21.4.1 Check

str(dots_partition(company = "Posit",
                   software = "RStudio",
                   "DSLC",
                   "Cohort 9"))
#> List of 2
#>  $ named  :List of 2
#>   ..$ company : chr "Posit"
#>   ..$ software: chr "RStudio"
#>  $ unnamed:List of 2
#>   ..$ : chr "DSLC"
#>   ..$ : chr "Cohort 9"

HTML Attributes

Found among the textbook’s source code

html_attributes <- function(list) {
  if (length(list) == 0) return("")

  attr <- map2_chr(names(list), list, html_attribute)
  paste0(" ", unlist(attr), collapse = "")
}
html_attribute <- function(name, value = NULL) {
  if (length(value) == 0) return(name) # for attributes with no value
  if (length(value) != 1) stop("`value` must be NULL or length 1")

  if (is.logical(value)) {
    # Convert T and F to true and false
    value <- tolower(value)
  } else {
    value <- escape_attr(value)
  }
  paste0(name, "='", value, "'")
}
escape_attr <- function(x) {
  x <- escape.character(x)
  x <- gsub("\'", '&#39;', x)
  x <- gsub("\"", '&quot;', x)
  x <- gsub("\r", '&#13;', x)
  x <- gsub("\n", '&#10;', x)
  x
}