Class: CodeGsubInstruction

Inherits:
Instruction show all
Defined in:
lib/instructions/code/code_gsub.rb

Overview

pops three items from the :code stack: the “host”, the “old_subtree” and the “new_subtree”; pushes a new :code item which contants the host, with every occurrence of the old_subtree (if any) replaced by the new_subtree

note: the order of arguments counts; the top :code stack item is the host, the second is the old_subtree, and the third is the new_subtree

needs: 3 :code

pushes: 1 :code

Instance Attribute Summary

Attributes inherited from Instruction

#context

Instance Method Summary collapse

Methods inherited from Instruction

all_instructions, #go, inherited, #initialize, #needs, #pushes, to_nudgecode

Constructor Details

This class inherits a constructor from Instruction

Instance Method Details

#cleanup ⇒ Object 



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# File 'lib/instructions/code/code_gsub.rb', line 40

def cleanup
  pushes :code, @result
end

#derive ⇒ Object

Raises:



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# File 'lib/instructions/code/code_gsub.rb', line 22

def derive
  new_tree = NudgeProgram.new(@new_subtree)
  raise InstructionMethodError,
    "#{self.class.to_nudgecode} cannot work with unparseable code" unless new_tree.parses?
  old_tree = NudgeProgram.new(@old_subtree)
  raise InstructionMethodError,
    "#{self.class.to_nudgecode} cannot work with unparseable code" unless old_tree.parses?
  host = NudgeProgram.new(@host_tree)
  raise InstructionMethodError,
    "#{self.class.to_nudgecode} cannot work with unparseable code" unless host.parses?
  
  found_at = [] # need to iterate through the tree the slow way to capture the indices (I think)
  host.linked_code.each_with_index do |point, index|
    found_at << (index+1) if point.blueprint == old_tree.blueprint
  end
  found_at.reverse.each {|index| host = host.replace_point(index, new_tree.linked_code)}
  @result = ValuePoint.new("code", host.blueprint)
end

#preconditions? ⇒ Boolean

was CODE.SUBST in Push3

Returns:

  • (Boolean) 


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# File 'lib/instructions/code/code_gsub.rb', line 14

def preconditions?
  needs :code, 3
end

#setup ⇒ Object 



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# File 'lib/instructions/code/code_gsub.rb', line 17

def setup
  @host_tree = @context.pop_value(:code)
  @old_subtree = @context.pop_value(:code)
  @new_subtree = @context.pop_value(:code)
end