Object
This will produce a compound array of simple diff change objects. Each element in the diffs array is a hunk or hunk array, where each element in each hunk array is a single Change object representing the addition or removal of a single element from one of the two tested sequences. The hunk provides the full context for the changes.
diffs = Diff::LCS.diff(seq1, seq2) # This example shows a simplified array format. # [ [ [ '-', 0, 'a' ] ], # 1 # [ [ '+', 2, 'd' ] ], # 2 # [ [ '-', 4, 'h' ], # 3 # [ '+', 4, 'f' ] ], # [ [ '+', 6, 'k' ] ], # 4 # [ [ '-', 8, 'n' ], # 5 # [ '-', 9, 'p' ], # [ '+', 9, 'r' ], # [ '+', 10, 's' ], # [ '+', 11, 't' ] ] ]
There are five hunks here. The first hunk says that the a at position 0 of the first sequence should be deleted ('-'). The second hunk says that the d at position 2 of the second sequence should be inserted ('+'). The third hunk says that the h at position 4 of the first sequence should be removed and replaced with the f from position 4 of the second sequence. The other two hunks are described similarly.
This callback object must be initialised and is used by the Diff::LCS#diff method.
cbo = Diff::LCS::DiffCallbacks.new Diff::LCS.LCS(seq1, seq2, cbo) cbo.finish
Note that the call to finish is absolutely necessary, or the last set of changes will not be visible. Alternatively, can be used as:
cbo = Diff::LCS::DiffCallbacks.new { |tcbo| Diff::LCS.LCS(seq1, seq2, tcbo) }
The necessary finish call will be made.
The simplified array format used in the example above can be obtained with:
require 'pp' pp diffs.map { |e| e.map { |f| f.to_a } }
# File lib/diff/lcs/callbacks.rb, line 134 def discard_a(event) @hunk << Diff::LCS::Change.new('-', event.old_position, event.old_element) end
# File lib/diff/lcs/callbacks.rb, line 138 def discard_b(event) @hunk << Diff::LCS::Change.new('+', event.new_position, event.new_element) end
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