Class Diff::LCS::SDiffCallbacks
In: lib/diff/lcs/callbacks.rb
Parent: Object

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

    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)

As with the other initialisable callback objects, Diff::LCS::SDiffCallbacks can be initialised with a block. As there is no “fininishing” to be done, this has no effect on the state of the object.

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

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 }

Methods

change   discard_a   discard_b   match   new  

Attributes

diffs  [R]  Returns the difference set collected during the diff process.

Public Class methods

Public Instance methods

[Validate]