Class: VirtualKeywords::IfRewriter

Inherits:
SexpProcessor
  • Object
show all
Defined in:
lib/virtual_keywords/keyword_rewriter.rb

Overview

SexpProcessor subclass that rewrites “if” expressions. Calls VirtualKeywords::REWRITTEN_KEYWORDS.call_if and lets it pick a virtual implementation.

Instance Method Summary collapse

Constructor Details

#initialize ⇒ IfRewriter

Initialize an IfRewriter (self.strict is false)



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# File 'lib/virtual_keywords/keyword_rewriter.rb', line 7

def initialize
  super
  self.strict = false
end

Instance Method Details

#rewrite_if(expression) ⇒ Object

Rewrite an :if sexp. SexpProcessor#process is a template method that will call this method every time it encounters an :if.

Arguments:

expression: (Sexp) the :if sexp to be rewritten.

Returns:

(Sexp) A rewritten sexp that calls
VirtualKeywords::REWRITTEN_KEYWORDS.call_if with the condition,
then clause, and else clause as arguments, all wrapped in lambdas.
It must also pass self to call_if, so REWRITTEN_KEYWORDS can decide
which of the lambdas registered with it should be called.



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# File 'lib/virtual_keywords/keyword_rewriter.rb', line 24

def rewrite_if(expression)
  # The sexp for the condition passed to if is inside expression[1]
  # We can further process this sexp if it has and/or in it.
  condition = expression[1]
  then_do = expression[2]
  else_do = expression[3]

  # This ugly sexp turns into the following Ruby code:
  # VirtualKeywords::REWRITTEN_KEYWORDS.call_if(
  #     self, lambda { condition }, lambda { then_do }, lambda { else_do })
  s(:call,
    s(:colon2,
      s(:const, :VirtualKeywords),
      :REWRITTEN_KEYWORDS
    ), :call_if,
    s(:array,
      s(:self),
      s(:iter, s(:fcall, :lambda), nil, condition),
      s(:iter, s(:fcall, :lambda), nil, then_do),
      s(:iter, s(:fcall, :lambda), nil, else_do)
    )
  )
end