Class: Oppen::ScanStack

Inherits:
Object
  • Object
show all
Extended by:
Mixins
Defined in:
lib/oppen/scan_stack.rb

Overview

A fixed-size stack that can be popped from top and bottom.

Instance Method Summary collapse

Methods included from Mixins

tokens_to_wadler, upsize_circular_array

Constructor Details

#initialize(size, config) ⇒ ScanStack

Returns a new instance of ScanStack.



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# File 'lib/oppen/scan_stack.rb', line 11

def initialize(size, config)
  @bottom = 0
  @config = config
  @empty = true
  @stack = Array.new(size)
  @top = 0
end

Instance Method Details

#bottom ⇒ Object

Returns:

  • (Object) 


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# File 'lib/oppen/scan_stack.rb', line 39

def bottom
  if empty?
    raise 'Accessing empty stack from bottom'
  end

  @stack[@bottom]
end

#decrement(index) ⇒ Integer

Decrement index (no overflow).

Parameters:

  • index (Integer)

Returns:

  • (Integer) 


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# File 'lib/oppen/scan_stack.rb', line 61

def decrement(index)
  (index - 1) % length
end

#empty? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/oppen/scan_stack.rb', line 20

def empty?
  @empty
end

#increment(index) ⇒ Integer

Increment index (no overflow).

Parameters:

  • index (Integer)

Returns:

  • (Integer) 


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# File 'lib/oppen/scan_stack.rb', line 52

def increment(index)
  (index + 1) % length
end

#length ⇒ Integer

Returns:

  • (Integer) 


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# File 'lib/oppen/scan_stack.rb', line 25

def length
  @stack.length
end

#pop ⇒ Nil

Pop a value from the top.

Returns:

  • (Nil) 


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# File 'lib/oppen/scan_stack.rb', line 87

def pop
  if empty?
    raise 'Popping empty stack from top'
  end

  res = top
  if @top == @bottom
    @empty = true
  else
    @top = decrement(@top)
  end
  res
end

#pop_bottom ⇒ Nil

Pop a value from the bottom.

Returns:

  • (Nil) 


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# File 'lib/oppen/scan_stack.rb', line 104

def pop_bottom
  if empty?
    raise 'Popping empty stack from bottom'
  end

  res = bottom
  if @top == @bottom
    @empty = true
  else
    @bottom = increment(@bottom)
  end
  res
end

#push(value) ⇒ Nil

Push a value to the top.

Parameters:

  • value (Object)

Returns:

  • (Nil) 


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# File 'lib/oppen/scan_stack.rb', line 70

def push(value)
  if empty?
    @empty = false
  else
    @top = increment(@top)
    if @top == @bottom
      raise 'Stack full' if !@config.upsize_stack?

      @stack, @bottom, @top = ScanStack.upsize_circular_array(@stack, @bottom)
    end
  end
  @stack[@top] = value
end

#top ⇒ Object

Returns:

  • (Object) 


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# File 'lib/oppen/scan_stack.rb', line 30

def top
  if empty?
    raise 'Accessing empty stack from top'
  end

  @stack[@top]
end

#update_indexes(offset) ⇒ Array[Integer]

Offset the values of the stack.

Parameters:

  • offset (Integer)

Returns:

  • (Array[Integer]) 


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# File 'lib/oppen/scan_stack.rb', line 123

def update_indexes(offset)
  @stack = @stack.map { |val|
    (val + offset) % length if val
  }
end