Class: Diff::LCS::SDiffCallbacks

Inherits:
Object
  • Object
show all
Defined in:
lib/diff/lcs/callbacks.rb

Overview

This will produce a simple array of diff change objects. Each element in the #diffs array is a single ContextChange. In the set of #diffs provided by SDiffCallbacks, both old and new objects will be presented for both changed and unchanged objects. nil will be substituted for a discarded object.

The diffset produced by this callback, when provided to Diff::LCS#sdiff, will compute and display the necessary components to show two sequences and their minimized differences side by side, just like the Unix utility sdiff.

# same             same
# before     |     after
# old        <     -
# -          >     new

seq1 = %w(a b c e h j l m n p)
seq2 = %w(b c d e f j k l m r s t)

diffs = Diff::LCS.sdiff(seq1, seq2)
# This example shows a simplified array format.
# [ [ "-", [  0, "a"], [  0, nil ] ],
#   [ "=", [  1, "b"], [  0, "b" ] ],
#   [ "=", [  2, "c"], [  1, "c" ] ],
#   [ "+", [  3, nil], [  2, "d" ] ],
#   [ "=", [  3, "e"], [  3, "e" ] ],
#   [ "!", [  4, "h"], [  4, "f" ] ],
#   [ "=", [  5, "j"], [  5, "j" ] ],
#   [ "+", [  6, nil], [  6, "k" ] ],
#   [ "=", [  6, "l"], [  7, "l" ] ],
#   [ "=", [  7, "m"], [  8, "m" ] ],
#   [ "!", [  8, "n"], [  9, "r" ] ],
#   [ "!", [  9, "p"], [ 10, "s" ] ],
#   [ "+", [ 10, nil], [ 11, "t" ] ] ]

The result of this operation is similar to that of Diff::LCS::ContextDiffCallbacks. They may be compared as:

s = Diff::LCS.sdiff(seq1, seq2).reject { |e| e.action == "=" }
c = Diff::LCS.sdiff(seq1, seq2, Diff::LCS::ContextDiffCallbacks).flatten(1)

s == c # => true

Use

This callback object must be initialised and is used by the Diff::LCS#sdiff method.

cbo = Diff::LCS::SDiffCallbacks.new
Diff::LCS.lcs(seq1, seq2, cbo)

This callback also supports initialization with a block, but as there is no "finishing" to be done, this has no effect on the state of the object.

result = Diff::LCS::SDiffCallbacks.new { |cbo| Diff::LCS.lcs(seq1, seq2, cbo) }

Simplified Array Format

The simplified array format used in the example above can be obtained with:

require 'pp'
pp diffs.map { |e| e.to_a }

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize {|_self| ... } ⇒ SDiffCallbacks

:yields: self

Yields:

  • (_self)

Yield Parameters:



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# File 'lib/diff/lcs/callbacks.rb', line 305

def initialize # :yields: self
  @diffs = []
  yield self if block_given?
end

Instance Attribute Details

#diffs ⇒ Object (readonly)

Returns the difference set collected during the diff process.



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# File 'lib/diff/lcs/callbacks.rb', line 303

def diffs
  @diffs
end

Instance Method Details

#change(event) ⇒ Object 



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# File 'lib/diff/lcs/callbacks.rb', line 322

def change(event)
  @diffs << Diff::LCS::ContextChange.simplify(event)
end

#discard_a(event) ⇒ Object 



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# File 'lib/diff/lcs/callbacks.rb', line 314

def discard_a(event)
  @diffs << Diff::LCS::ContextChange.simplify(event)
end

#discard_b(event) ⇒ Object 



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# File 'lib/diff/lcs/callbacks.rb', line 318

def discard_b(event)
  @diffs << Diff::LCS::ContextChange.simplify(event)
end

#match(event) ⇒ Object 



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# File 'lib/diff/lcs/callbacks.rb', line 310

def match(event)
  @diffs << Diff::LCS::ContextChange.simplify(event)
end