R Markdown with Alternate Languages

The purpose of this document is to demonstrate that an R Markdown document can display syntax highlighting for languages that are not supported natively by R Markdown. Highlighting is actually supported by pandoc and the skylighting Haskell library. A full list of languages supported by pandoc can be found here.

The original reason for working through this was to enable SAS syntax highlighting within an R Markdown html document.

For a full description of how this is accomplished and stitched together, refer to my blog post.

Requirements

The following R packages are required for the proposed solution.

In addition, one will need access to the internet as the solution makes use of <script> tags to read in Javascript libraries from a CDN.

Languages

SAS

Below is an example of highlighting SAS code. The code was taken from the CodeMirror example page.

Crystal

Below is an example of highlighting Crystal code. The code was taken from the CodeMirror example page.

# Features of Crystal
# - Ruby-inspired syntax.
# - Statically type-checked but without having to specify the type of variables or method arguments.
# - Be able to call C code by writing bindings to it in Crystal.
# - Have compile-time evaluation and generation of code, to avoid boilerplate code.
# - Compile to efficient native code.

# A very basic HTTP server
require "http/server"

server = HTTP::Server.new(8080) do |request|
  HTTP::Response.ok "text/plain", "Hello world, got #{request.path}!"
end

puts "Listening on http://0.0.0.0:8080"
server.listen

module Foo
  abstract def abstract_method : String

@[AlwaysInline]
  def with_foofoo
    with Foo.new(self) yield
  end

struct Foo
    def initialize(@foo : ::Foo)
    end

def hello_world
      @foo.abstract_method
    end
  end
end

class Bar
  include Foo

@@foobar = 12345

def initialize(@bar : Int32)
  end

macro alias_method(name, method)
    def {{ name }}(*args)
      {{ method }}(*args)
    end
  end

def a_method
    "Hello, World"
  end

alias_method abstract_method, a_method

def show_instance_vars : Nil
    {% for var in @type.instance_vars %}
      puts "@{{ var }} = #{ @{{ var }} }"
    {% end %}
  end
end

class Baz < Bar; end

lib LibC
  fun c_puts = "puts"(str : Char*) : Int
end

baz = Baz.new(100)
baz.show_instance_vars
baz.with_foofoo do
  LibC.c_puts hello_world
end

R Markdown with Alternate Languages

Curtis Alexander

Requirements

Languages

SAS

Crystal