Contents:

1. Introduction

Introduction to be written.

2. Overview

〈Overview〉 ≡

macro: func [spec body] [
 spec: use spec reduce [spec]
 reduce ['macro spec body]
]
expand-macros: func [code] [
 either function? :code [
  func third :code expand-macros second :code
 ] [
  collect/into [
   parse code code-rule
  ] make code 0
 ]
]
value: none
code-rule: [
 some [
  set value word! (
   either all [
    value? value
    block? m: get value
    not empty? m
    m/1 = 'macro
   ] [
    next-rule: macro-args-rule
    nargs: length? m/2
   ] [
    next-rule: none
    keep value
   ]
  )
  next-rule
  |
  set value [block! | paren!] (keep/only expand-macros value)
  |
  set value skip (keep/only :value)
 ]
]
macro-args-rule: [
 copy value nargs skip (
  expand-macro value m
 )
 |
 (make error! "not enough arguments!")
]
expand-macro: func [args macro /local value argument here] [
 if block? args [
  parse args [
   some [
    here: paren! (here/1: expand-macros here/1)
    |
    skip
   ]
  ]
 ]
 either empty? macro/2 [
  argument: [end skip]
  args: none
 ] [
  set macro/2 args
  args: bind? macro/2/1
  argument: collect [
   keep to lit-word! first macro/2
   foreach w next macro/2 [
    keep '| keep to lit-word! w
   ]
  ]
 ]
 expand-macro* macro/3 argument args
]
expand-macro*: func [block argument args] [
 parse block [
  some [
   set value argument (
    keep get in args value
   )
   |
   value: path! :value into [set value argument 'only] (
    keep/only get in args value
   )
   |
   /lit set value [block! | paren!] (keep/only value)
   |
   /paren set value paren! (keep/only collect/into [expand-macro* value argument args] make paren! 0)
   |
   /only set value paren! (keep/only do either args [bind to block! value args] [value])
   |
   set value paren! (keep do either args [bind to block! value args] [value])
   |
   set value block! (
    keep/only collect [expand-macro* value argument args]
   )
   |
   set value skip (keep/only :value)
  ]
 ]
]