# Module: Diff::LCS

Included in:
Array, String
Defined in:
lib/diff/lcs.rb,
lib/diff/lcs.rb,
lib/diff/lcs/callbacks.rb

## How Diff Works (by Mark-Jason Dominus)

I once read an article written by the authors of `diff`; they said that they hard worked very hard on the algorithm until they found the right one.

I think what they ended up using (and I hope someone will correct me, because I am not very confident about this) was the `longest common subsequence' method. In the LCS problem, you have two sequences of items:

``````a b c d f g h j q z
a b c d e f g i j k r x y z
``````

and you want to find the longest sequence of items that is present in both original sequences in the same order. That is, you want to find a new sequence S which can be obtained from the first sequence by deleting some items, and from the second sequence by deleting other items. You also want S to be as long as possible. In this case S is:

``````a b c d f g j z
``````

From there it's only a small step to get diff-like output:

``````e   h i   k   q r x y
+   - +   +   - + + +
``````

This module solves the LCS problem. It also includes a canned function to generate `diff`-like output.

It might seem from the example above that the LCS of two sequences is always pretty obvious, but that's not always the case, especially when the two sequences have many repeated elements. For example, consider

``````a x b y c z p d q
a b c a x b y c z
``````

A naive approach might start by matching up the `a` and `b` that appear at the beginning of each sequence, like this:

``````a x b y c         z p d q
a   b   c a b y c z
``````

This finds the common subsequence a b c z. But actually, the LCS is a x b y c z:

``````      a x b y c z p d q
a b c a x b y c z
``````

## Constant Summary collapse

VERSION =
`"1.5.0"`
PATCH_MAP =

standard:disable Style/HashSyntax

```{ # :nodoc:
:patch => {"+" => "+", "-" => "-", "!" => "!", "=" => "="}.freeze,
:unpatch => {"+" => "-", "-" => "+", "!" => "!", "=" => "="}.freeze
}.freeze```
SequenceCallbacks =

An alias for DefaultCallbacks that is used in Diff::LCS#traverse_sequences.

``````Diff::LCS.LCS(seq1, seq2, Diff::LCS::SequenceCallbacks)
``````
`DefaultCallbacks`
BalancedCallbacks =

An alias for DefaultCallbacks that is used in Diff::LCS#traverse_balanced.

``````Diff::LCS.LCS(seq1, seq2, Diff::LCS::BalancedCallbacks)
``````
`DefaultCallbacks`

## Class Method Summary collapse

• #diff computes the smallest set of additions and deletions necessary to turn the first sequence into the second, and returns a description of these changes.

• .lcs(seq1, seq2, &block) ⇒ Object (also: LCS)

:yields: seq1 for each matched.

• Applies a `patchset` to the sequence `src` according to the `direction` (`:patch` or `:unpatch`), producing a new sequence.

• Given a set of patchset, convert the current version to the next version.

• #sdiff computes all necessary components to show two sequences and their minimized differences side by side, just like the Unix utility sdiff does:.

• #traverse_balanced is an alternative to #traverse_sequences.

• #traverse_sequences is the most general facility provided by this module; #diff and #lcs are implemented as calls to it.

• Given a set of patchset, convert the current version to the prior version.

## Instance Method Summary collapse

• Returns the difference set between `self` and `other`.

• Returns an Array containing the longest common subsequence(s) between `self` and `other`.

• Attempts to patch `self` with the provided `patchset`.

• Attempts to patch `self` with the provided `patchset`.

• Attempts to patch `self` with the provided `patchset`, using #patch!.

• Returns the balanced (“side-by-side”) difference set between `self` and `other`.

• Traverses the discovered longest common subsequences between `self` and `other` using the alternate, balanced algorithm.

• Traverses the discovered longest common subsequences between `self` and `other`.

• Attempts to patch `self` with the provided `patchset`.

• Attempts to unpatch `self` with the provided `patchset`.

• Attempts to unpatch `self` with the provided `patchset`, using #unpatch!.

## Class Method Details

### .callbacks_for(callbacks) ⇒ Object

 ``` 52 53 54 55 56``` ```# File 'lib/diff/lcs/callbacks.rb', line 52 def self.callbacks_for(callbacks) callbacks.new rescue callbacks end```

### .diff(seq1, seq2, callbacks = nil, &block) ⇒ Object

#diff computes the smallest set of additions and deletions necessary to turn the first sequence into the second, and returns a description of these changes.

See Diff::LCS::DiffCallbacks for the default behaviour. An alternate behaviour may be implemented with Diff::LCS::ContextDiffCallbacks. If a Class argument is provided for `callbacks`, #diff will attempt to initialise it. If the `callbacks` object (possibly initialised) responds to #finish, it will be called.

 ``` 168 169 170``` ```# File 'lib/diff/lcs.rb', line 168 def diff(seq1, seq2, callbacks = nil, &block) # :yields: diff changes diff_traversal(:diff, seq1, seq2, callbacks || Diff::LCS::DiffCallbacks, &block) end```

### .diff_traversal(method, seq1, seq2, callbacks, &block) ⇒ Object

 ``` 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25``` ```# File 'lib/diff/lcs/internals.rb', line 4 def diff_traversal(method, seq1, seq2, callbacks, &block) callbacks = callbacks_for(callbacks) case method when :diff traverse_sequences(seq1, seq2, callbacks) when :sdiff traverse_balanced(seq1, seq2, callbacks) end callbacks.finish if callbacks.respond_to? :finish if block callbacks.diffs.map do |hunk| if hunk.is_a? Array hunk.map { |hunk_block| block[hunk_block] } else block[hunk] end end else callbacks.diffs end end```

### .lcs(seq1, seq2, &block) ⇒ ObjectAlso known as: LCS

:yields: seq1 for each matched

 ``` 144 145 146 147 148 149 150 151 152 153 154 155 156``` ```# File 'lib/diff/lcs.rb', line 144 def lcs(seq1, seq2, &block) # :yields: seq1[i] for each matched matches = Diff::LCS::Internals.lcs(seq1, seq2) ret = [] string = seq1.is_a? String matches.each_index do |i| next if matches[i].nil? v = string ? seq1[i, 1] : seq1[i] v = block[v] if block ret << v end ret end```

### .patch(src, patchset, direction = nil) ⇒ Object

Applies a `patchset` to the sequence `src` according to the `direction` (`:patch` or `:unpatch`), producing a new sequence.

If the `direction` is not specified, Diff::LCS::patch will attempt to discover the direction of the `patchset`.

A `patchset` can be considered to apply forward (`:patch`) if the following expression is true:

``````patch(s1, diff(s1, s2)) -> s2
``````

A `patchset` can be considered to apply backward (`:unpatch`) if the following expression is true:

``````patch(s2, diff(s1, s2)) -> s1
``````

If the `patchset` contains no changes, the `src` value will be returned as either `src.dup` or `src`. A `patchset` can be deemed as having no changes if the following predicate returns true:

``````patchset.empty? or
patchset.flatten(1).all? { |change| change.unchanged? }
``````

### Patchsets

A `patchset` is always an enumerable sequence of changes, hunks of changes, or a mix of the two. A hunk of changes is an enumerable sequence of changes:

``````[ # patchset
# change
[ # hunk
# change
]
]
``````

The `patch` method accepts `patchset`s that are enumerable sequences containing either Diff::LCS::Change objects (or a subclass) or the array representations of those objects. Prior to application, array representations of Diff::LCS::Change objects will be reified.

 ``` 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726``` ```# File 'lib/diff/lcs.rb', line 626 def patch(src, patchset, direction = nil) # Normalize the patchset. has_changes, patchset = Diff::LCS::Internals.analyze_patchset(patchset) return src.respond_to?(:dup) ? src.dup : src unless has_changes string = src.is_a?(String) # Start with a new empty type of the source's class res = src.class.new direction ||= Diff::LCS::Internals.intuit_diff_direction(src, patchset) ai = bj = 0 patch_map = PATCH_MAP[direction] patchset.each do |change| # Both Change and ContextChange support #action action = patch_map[change.action] case change when Diff::LCS::ContextChange case direction when :patch el = change.new_element op = change.old_position np = change.new_position when :unpatch el = change.old_element op = change.new_position np = change.old_position end case action when "-" # Remove details from the old string while ai < op res << (string ? src[ai, 1] : src[ai]) ai += 1 bj += 1 end ai += 1 when "+" while bj < np res << (string ? src[ai, 1] : src[ai]) ai += 1 bj += 1 end res << el bj += 1 when "=" # This only appears in sdiff output with the SDiff callback. # Therefore, we only need to worry about dealing with a single # element. res << el ai += 1 bj += 1 when "!" while ai < op res << (string ? src[ai, 1] : src[ai]) ai += 1 bj += 1 end bj += 1 ai += 1 res << el end when Diff::LCS::Change case action when "-" while ai < change.position res << (string ? src[ai, 1] : src[ai]) ai += 1 bj += 1 end ai += 1 when "+" while bj < change.position res << (string ? src[ai, 1] : src[ai]) ai += 1 bj += 1 end bj += 1 res << change.element end end end while ai < src.size res << (string ? src[ai, 1] : src[ai]) ai += 1 bj += 1 end res end```

### .patch!(src, patchset) ⇒ Object

Given a set of patchset, convert the current version to the next version. Does no auto-discovery.

 ``` 736 737 738``` ```# File 'lib/diff/lcs.rb', line 736 def patch!(src, patchset) patch(src, patchset, :patch) end```

### .sdiff(seq1, seq2, callbacks = nil, &block) ⇒ Object

#sdiff computes all necessary components to show two sequences and their minimized differences side by side, just like the Unix utility sdiff does:

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

See Diff::LCS::SDiffCallbacks for the default behaviour. An alternate behaviour may be implemented with Diff::LCS::ContextDiffCallbacks. If a Class argument is provided for `callbacks`, #diff will attempt to initialise it. If the `callbacks` object (possibly initialised) responds to #finish, it will be called.

Each element of a returned array is a Diff::LCS::ContextChange object, which can be implicitly converted to an array.

``````Diff::LCS.sdiff(a, b).each do |action, (old_pos, old_element), (new_pos, new_element)|
case action
when '!'
# replace
when '-'
# delete
when '+'
# insert
end
end
``````
 ``` 200 201 202``` ```# File 'lib/diff/lcs.rb', line 200 def sdiff(seq1, seq2, callbacks = nil, &block) # :yields: diff changes diff_traversal(:sdiff, seq1, seq2, callbacks || Diff::LCS::SDiffCallbacks, &block) end```

### .traverse_balanced(seq1, seq2, callbacks = Diff::LCS::BalancedCallbacks) ⇒ Object

#traverse_balanced is an alternative to #traverse_sequences. It uses a different algorithm to iterate through the entries in the computed longest common subsequence. Instead of viewing the changes as insertions or deletions from one of the sequences, #traverse_balanced will report changes between the sequences.

The arguments to #traverse_balanced are the two sequences to traverse and a callback object, like this:

``````traverse_balanced(seq1, seq2, Diff::LCS::ContextDiffCallbacks.new)
``````

#sdiff is implemented with #traverse_balanced.

## Callback Methods

Optional callback methods are emphasized.

callbacks#match

Called when `a` and `b` are pointing to common elements in `A` and `B`.

Called when `a` is pointing to an element not in `B`.

Called when `b` is pointing to an element not in `A`.

callbacks#change

Called when `a` and `b` are pointing to the same relative position, but `A[a]` and `B[b]` are not the same; a change has occurred.

#traverse_balanced might be a bit slower than #traverse_sequences, noticable only while processing huge amounts of data.

## Algorithm

``````a---+
v
A = a b c e h j l m n p
B = b c d e f j k l m r s t
^
b---+
``````

### Matches

If there are two arrows (`a` and `b`) pointing to elements of sequences `A` and `B`, the arrows will initially point to the first elements of their respective sequences. #traverse_sequences will advance the arrows through the sequences one element at a time, calling a method on the user-specified callback object before each advance. It will advance the arrows in such a way that if there are elements `A[i]` and `B[j]` which are both equal and part of the longest common subsequence, there will be some moment during the execution of #traverse_sequences when arrow `a` is pointing to `A[i]` and arrow `b` is pointing to `B[j]`. When this happens, #traverse_sequences will call `callbacks#match` and then it will advance both arrows.

Otherwise, one of the arrows is pointing to an element of its sequence that is not part of the longest common subsequence. #traverse_sequences will advance that arrow and will call `callbacks#discard_a` or `callbacks#discard_b`, depending on which arrow it advanced.

### Changes

If both `a` and `b` point to elements that are not part of the longest common subsequence, then #traverse_sequences will try to call `callbacks#change` and advance both arrows. If `callbacks#change` is not implemented, then `callbacks#discard_a` and `callbacks#discard_b` will be called in turn.

The methods for `callbacks#match`, `callbacks#discard_a`, `callbacks#discard_b`, and `callbacks#change` are invoked with an event comprising the action (“=”, “+”, “-”, or “!”, respectively), the indicies `i` and `j`, and the elements `A[i]` and `B[j]`. Return values are discarded by #traverse_balanced.

### Context

Note that `i` and `j` may not be the same index position, even if `a` and `b` are considered to be pointing to matching or changed elements.

 ``` 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577``` ```# File 'lib/diff/lcs.rb', line 475 def traverse_balanced(seq1, seq2, callbacks = Diff::LCS::BalancedCallbacks) matches = Diff::LCS::Internals.lcs(seq1, seq2) a_size = seq1.size b_size = seq2.size ai = bj = mb = 0 ma = -1 string = seq1.is_a?(String) # Process all the lines in the match vector. loop do # Find next match indices +ma+ and +mb+ loop do ma += 1 break unless ma < matches.size && matches[ma].nil? end break if ma >= matches.size # end of matches? mb = matches[ma] # Change(seq2) while (ai < ma) || (bj < mb) ax = string ? seq1[ai, 1] : seq1[ai] bx = string ? seq2[bj, 1] : seq2[bj] case [(ai < ma), (bj < mb)] when [true, true] if callbacks.respond_to?(:change) event = Diff::LCS::ContextChange.new("!", ai, ax, bj, bx) event = yield event if block_given? callbacks.change(event) ai += 1 else event = Diff::LCS::ContextChange.new("-", ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_a(event) ai += 1 ax = string ? seq1[ai, 1] : seq1[ai] event = Diff::LCS::ContextChange.new("+", ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_b(event) end bj += 1 when [true, false] event = Diff::LCS::ContextChange.new("-", ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_a(event) ai += 1 when [false, true] event = Diff::LCS::ContextChange.new("+", ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_b(event) bj += 1 end end # Match ax = string ? seq1[ai, 1] : seq1[ai] bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new("=", ai, ax, bj, bx) event = yield event if block_given? callbacks.match(event) ai += 1 bj += 1 end while (ai < a_size) || (bj < b_size) ax = string ? seq1[ai, 1] : seq1[ai] bx = string ? seq2[bj, 1] : seq2[bj] case [(ai < a_size), (bj < b_size)] when [true, true] if callbacks.respond_to?(:change) event = Diff::LCS::ContextChange.new("!", ai, ax, bj, bx) event = yield event if block_given? callbacks.change(event) ai += 1 else event = Diff::LCS::ContextChange.new("-", ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_a(event) ai += 1 ax = string ? seq1[ai, 1] : seq1[ai] event = Diff::LCS::ContextChange.new("+", ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_b(event) end bj += 1 when [true, false] event = Diff::LCS::ContextChange.new("-", ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_a(event) ai += 1 when [false, true] event = Diff::LCS::ContextChange.new("+", ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_b(event) bj += 1 end end end```

### .traverse_sequences(seq1, seq2, callbacks = Diff::LCS::SequenceCallbacks) ⇒ Object

#traverse_sequences is the most general facility provided by this module; #diff and #lcs are implemented as calls to it.

The arguments to #traverse_sequences are the two sequences to traverse, and a callback object, like this:

``````traverse_sequences(seq1, seq2, Diff::LCS::ContextDiffCallbacks.new)
``````

## Callback Methods

Optional callback methods are emphasized.

callbacks#match

Called when `a` and `b` are pointing to common elements in `A` and `B`.

Called when `a` is pointing to an element not in `B`.

Called when `b` is pointing to an element not in `A`.

callbacks#finished_a

Called when `a` has reached the end of sequence `A`.

callbacks#finished_b

Called when `b` has reached the end of sequence `B`.

## Algorithm

``````a---+
v
A = a b c e h j l m n p
B = b c d e f j k l m r s t
^
b---+
``````

If there are two arrows (`a` and `b`) pointing to elements of sequences `A` and `B`, the arrows will initially point to the first elements of their respective sequences. #traverse_sequences will advance the arrows through the sequences one element at a time, calling a method on the user-specified callback object before each advance. It will advance the arrows in such a way that if there are elements `A[i]` and `B[j]` which are both equal and part of the longest common subsequence, there will be some moment during the execution of #traverse_sequences when arrow `a` is pointing to `A[i]` and arrow `b` is pointing to `B[j]`. When this happens, #traverse_sequences will call `callbacks#match` and then it will advance both arrows.

Otherwise, one of the arrows is pointing to an element of its sequence that is not part of the longest common subsequence. #traverse_sequences will advance that arrow and will call `callbacks#discard_a` or `callbacks#discard_b`, depending on which arrow it advanced. If both arrows point to elements that are not part of the longest common subsequence, then #traverse_sequences will advance arrow `a` and call the appropriate callback, then it will advance arrow `b` and call the appropriate callback.

The methods for `callbacks#match`, `callbacks#discard_a`, and `callbacks#discard_b` are invoked with an event comprising the action (“=”, “+”, or “-”, respectively), the indicies `i` and `j`, and the elements `A[i]` and `B[j]`. Return values are discarded by #traverse_sequences.

### End of Sequences

If arrow `a` reaches the end of its sequence before arrow `b` does, #traverse_sequence will try to call `callbacks#finished_a` with the last index and element of `A` (`A[-1]`) and the current index and element of `B` (`B[j]`). If `callbacks#finished_a` does not exist, then `callbacks#discard_b` will be called on each element of `B` until the end of the sequence is reached (the call will be done with `A[-1]` and `B[j]` for each element).

If `b` reaches the end of `B` before `a` reaches the end of `A`, `callbacks#finished_b` will be called with the current index and element of `A` (`A[i]`) and the last index and element of `B` (`A[-1]`). Again, if `callbacks#finished_b` does not exist on the callback object, then `callbacks#discard_a` will be called on each element of `A` until the end of the sequence is reached (`A[i]` and `B[-1]`).

There is a chance that one additional `callbacks#discard_a` or `callbacks#discard_b` will be called after the end of the sequence is reached, if `a` has not yet reached the end of `A` or `b` has not yet reached the end of `B`.

 ``` 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392``` ```# File 'lib/diff/lcs.rb', line 285 def traverse_sequences(seq1, seq2, callbacks = Diff::LCS::SequenceCallbacks) # :yields: change events callbacks ||= Diff::LCS::SequenceCallbacks matches = Diff::LCS::Internals.lcs(seq1, seq2) run_finished_a = run_finished_b = false string = seq1.is_a?(String) a_size = seq1.size b_size = seq2.size ai = bj = 0 matches.each do |b_line| if b_line.nil? unless seq1[ai].nil? ax = string ? seq1[ai, 1] : seq1[ai] bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new("-", ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_a(event) end else ax = string ? seq1[ai, 1] : seq1[ai] loop do break unless bj < b_line bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new("+", ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_b(event) bj += 1 end bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new("=", ai, ax, bj, bx) event = yield event if block_given? callbacks.match(event) bj += 1 end ai += 1 end # The last entry (if any) processed was a match. +ai+ and +bj+ point just # past the last matching lines in their sequences. while (ai < a_size) || (bj < b_size) # last A? if ai == a_size && bj < b_size if callbacks.respond_to?(:finished_a) && !run_finished_a ax = string ? seq1[-1, 1] : seq1[-1] bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new(">", (a_size - 1), ax, bj, bx) event = yield event if block_given? callbacks.finished_a(event) run_finished_a = true else ax = string ? seq1[ai, 1] : seq1[ai] loop do bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new("+", ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_b(event) bj += 1 break unless bj < b_size end end end # last B? if bj == b_size && ai < a_size if callbacks.respond_to?(:finished_b) && !run_finished_b ax = string ? seq1[ai, 1] : seq1[ai] bx = string ? seq2[-1, 1] : seq2[-1] event = Diff::LCS::ContextChange.new("<", ai, ax, (b_size - 1), bx) event = yield event if block_given? callbacks.finished_b(event) run_finished_b = true else bx = string ? seq2[bj, 1] : seq2[bj] loop do ax = string ? seq1[ai, 1] : seq1[ai] event = Diff::LCS::ContextChange.new("-", ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_a(event) ai += 1 break unless bj < b_size end end end if ai < a_size ax = string ? seq1[ai, 1] : seq1[ai] bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new("-", ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_a(event) ai += 1 end if bj < b_size ax = string ? seq1[ai, 1] : seq1[ai] bx = string ? seq2[bj, 1] : seq2[bj] event = Diff::LCS::ContextChange.new("+", ai, ax, bj, bx) event = yield event if block_given? callbacks.discard_b(event) bj += 1 end end end```

### .unpatch!(src, patchset) ⇒ Object

Given a set of patchset, convert the current version to the prior version. Does no auto-discovery.

 ``` 730 731 732``` ```# File 'lib/diff/lcs.rb', line 730 def unpatch!(src, patchset) patch(src, patchset, :unpatch) end```

## Instance Method Details

### #diff(other, callbacks = nil, &block) ⇒ Object

Returns the difference set between `self` and `other`. See Diff::LCS#diff.

 ``` 75 76 77``` ```# File 'lib/diff/lcs.rb', line 75 def diff(other, callbacks = nil, &block) Diff::LCS.diff(self, other, callbacks, &block) end```

### #lcs(other, &block) ⇒ Object

Returns an Array containing the longest common subsequence(s) between `self` and `other`. See Diff::LCS#lcs.

``````lcs = seq1.lcs(seq2)
``````

A note when using objects: Diff::LCS only works properly when each object can be used as a key in a Hash, which typically means that the objects must implement Object#eql? in a way that two identical values compare identically for key purposes. That is:

``````O.new('a').eql?(O.new('a')) == true
``````
 ``` 70 71 72``` ```# File 'lib/diff/lcs.rb', line 70 def lcs(other, &block) # :yields: self[i] if there are matched subsequences Diff::LCS.lcs(self, other, &block) end```

### #patch(patchset) ⇒ Object

Attempts to patch `self` with the provided `patchset`. A new sequence based on `self` and the `patchset` will be created. See Diff::LCS#patch. Attempts to autodiscover the direction of the patch.

 ``` 101 102 103``` ```# File 'lib/diff/lcs.rb', line 101 def patch(patchset) Diff::LCS.patch(self, patchset) end```

### #patch!(patchset) ⇒ Object

Attempts to patch `self` with the provided `patchset`. A new sequence based on `self` and the `patchset` will be created. See Diff::LCS#patch. Does no patch direction autodiscovery.

 ``` 109 110 111``` ```# File 'lib/diff/lcs.rb', line 109 def patch!(patchset) Diff::LCS.patch!(self, patchset) end```

### #patch_me(patchset) ⇒ Object

Attempts to patch `self` with the provided `patchset`, using #patch!. If the sequence this is used on supports #replace, the value of `self` will be replaced. See Diff::LCS#patch. Does no patch direction autodiscovery.

 ``` 123 124 125 126 127 128 129``` ```# File 'lib/diff/lcs.rb', line 123 def patch_me(patchset) if respond_to? :replace replace(patch!(patchset)) else patch!(patchset) end end```

### #sdiff(other, callbacks = nil, &block) ⇒ Object

Returns the balanced (“side-by-side”) difference set between `self` and `other`. See Diff::LCS#sdiff.

 ``` 81 82 83``` ```# File 'lib/diff/lcs.rb', line 81 def sdiff(other, callbacks = nil, &block) Diff::LCS.sdiff(self, other, callbacks, &block) end```

### #traverse_balanced(other, callbacks = nil, &block) ⇒ Object

Traverses the discovered longest common subsequences between `self` and `other` using the alternate, balanced algorithm. See Diff::LCS#traverse_balanced.

 ``` 94 95 96``` ```# File 'lib/diff/lcs.rb', line 94 def traverse_balanced(other, callbacks = nil, &block) Diff::LCS.traverse_balanced(self, other, callbacks || Diff::LCS::BalancedCallbacks, &block) end```

### #traverse_sequences(other, callbacks = nil, &block) ⇒ Object

Traverses the discovered longest common subsequences between `self` and `other`. See Diff::LCS#traverse_sequences.

 ``` 87 88 89``` ```# File 'lib/diff/lcs.rb', line 87 def traverse_sequences(other, callbacks = nil, &block) Diff::LCS.traverse_sequences(self, other, callbacks || Diff::LCS::SequenceCallbacks, &block) end```

### #unpatch ⇒ Object

Attempts to patch `self` with the provided `patchset`. A new sequence based on `self` and the `patchset` will be created. See Diff::LCS#patch. Attempts to autodiscover the direction of the patch.

 ``` 104 105 106``` ```# File 'lib/diff/lcs.rb', line 104 def patch(patchset) Diff::LCS.patch(self, patchset) end```

### #unpatch!(patchset) ⇒ Object

Attempts to unpatch `self` with the provided `patchset`. A new sequence based on `self` and the `patchset` will be created. See Diff::LCS#unpatch. Does no patch direction autodiscovery.

 ``` 116 117 118``` ```# File 'lib/diff/lcs.rb', line 116 def unpatch!(patchset) Diff::LCS.unpatch!(self, patchset) end```

### #unpatch_me(patchset) ⇒ Object

Attempts to unpatch `self` with the provided `patchset`, using #unpatch!. If the sequence this is used on supports #replace, the value of `self` will be replaced. See Diff::LCS#unpatch. Does no patch direction autodiscovery.

 ``` 134 135 136 137 138 139 140``` ```# File 'lib/diff/lcs.rb', line 134 def unpatch_me(patchset) if respond_to? :replace replace(unpatch!(patchset)) else unpatch!(patchset) end end```