Class: Rewrite::DefVar

Inherits:
Object
  • Object
show all
Defined in:
lib/rewrite/def_var.rb

Overview

Hygienically define a variable to be used in a chunk of code.

Defvar.new(:name, definition).process(exp)
  => lambda { |name|
       exp
     }.call(definition)

This is useful when you want to wrap some code in a let.

There’s an olptimization so that you can nest it without penalty:

Defvar.new(:name1, definition1).process(
  Defvar.new(:name2, definition2).process(exp)
) => lambda { |name1, name2|
       exp
     }.call(definition1, definition2)

Instance Method Summary collapse

Constructor Details

#initialize(sym, sexp) ⇒ DefVar

Returns a new instance of DefVar.



29
30
31
 
# File 'lib/rewrite/def_var.rb', line 29

def initialize(sym, sexp)
  @sym, @sexp = sym, sexp
end

Instance Method Details

#process(sexp) ⇒ Object 



33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
 
# File 'lib/rewrite/def_var.rb', line 33

def process(sexp)
  if sexp.length >= 3 && sexp[0] == :call && sexp[2] == :call &&
      (callee = sexp[1]) && callee.length >= 4 && callee[0] == :iter && callee[1].to_a == [:fcall, :lambda]
    parameters = callee[2]
    if parameters.nil?
      callee[2] = s(:dasgn_curr, @sym)
      s(:call,
        callee,
        :call,
        s(:array, @sexp)
      )
    elsif parameters[0] == :dasgn || parameters[0] == :dasgn_curr
      callee[2] = s(:masgn,
        s(:array,
          s(:dasgn_curr, parameters[1]),
          s(:dasgn_curr, @sym)
        )
      )
      s(:call,
        callee,
        :call,
        sexp[3] + [ @sexp ]
      )
    elsif parameters[0] == :masgn
      callee[2][1] << s(:dasgn_curr, @sym)
      s(:call,
        callee,
        :call,
        sexp[3] + [ @sexp ]
      )
    else
      raise "Confused by #{Ruby2Ruby.new.process(parameters)}"
    end
  else
    s(:call,
      s(:iter,
        s(:fcall, :lambda),
        s(:dasgn_curr, @sym),
        sexp
      ),
      :call,
      s(:array, @sexp)
    )
  end
end