Make the syntax for updating variables common.

Stream: Is there code for X?

[Asei Inoue]

This is a part of my code in mdgen:

/-- new notaion to represent `x := x ++ e`. -/
syntax ident "++=" term : doElem

macro_rules
  | `(doElem| $x:ident ++= $e:term) => `(doElem| ($x) := ($x) ++ ($e))

/-- A chunk of grouped code for conversion to markdown. -/
structure Block where
  content : String
  toCodeBlock : Bool
  deriving Repr

private def buildBlocks (lines : List String) : List Block := Id.run do
  let mut toCodeBlock := true
  let mut blocks : List Block := []
  let mut content := ""
  for line in lines do
    if line.endsWith "--#" then
      continue

    if line.startsWith "/-" && ! line.startsWith "/--" then
      blocks ++= [{content := content.trim, toCodeBlock := toCodeBlock}]
      toCodeBlock := ! toCodeBlock
      content := line ++ "\n"

      if line.endsWith "-/" then
        blocks ++= [{content := content.trim, toCodeBlock := toCodeBlock}]
        toCodeBlock := ! toCodeBlock
        content := ""

    else if line.endsWith "-/" && ! toCodeBlock then
      content ++= line
      blocks ++= [{content := content.trim, toCodeBlock := toCodeBlock}]
      toCodeBlock := ! toCodeBlock
      content := ""
    else
      content ++= line ++ "\n"

  if content != "" then
    blocks ++= [{content := content.trim, toCodeBlock := toCodeBlock}]
  return blocks

The following codes appear repeatedly in the above code:

      blocks ++= [{content := content.trim, toCodeBlock := toCodeBlock}]
      toCodeBlock := ! toCodeBlock

Could this be made common? Obviously this can be done using macros, but I want to make it common as a function rather than a macro.
Thank you.