NAME¶
Algorithm::Merge - Three-way merge and diff
SYNOPSIS¶
use Algorithm::Merge qw(merge diff3 traverse_sequences3);
@merged = merge(\@ancestor, \@a, \@b, {
CONFLICT => sub { }
});
@merged = merge(\@ancestor, \@a, \@b, {
CONFLICT => sub { }
}, $key_generation_function);
$merged = merge(\@ancestor, \@a, \@b, {
CONFLICT => sub { }
});
$merged = merge(\@ancestor, \@a, \@b, {
CONFLICT => sub { }
}, $key_generation_function);
@diff = diff3(\@ancestor, \@a, \@b);
@diff = diff3(\@ancestor, \@a, \@b, $key_generation_function);
$diff = diff3(\@ancestor, \@a, \@b);
$diff = diff3(\@ancestor, \@a, \@b, $key_generation_function);
@trav = traverse_sequences3(\@ancestor, \@a, \@b, {
# callbacks
});
@trav = traverse_sequences3(\@ancestor, \@a, \@b, {
# callbacks
}, $key_generation_function);
$trav = traverse_sequences3(\@ancestor, \@a, \@b, {
# callbacks
});
$trav = traverse_sequences3(\@ancestor, \@a, \@b, {
# callbacks
}, $key_generation_function);
USAGE¶
This module complements Algorithm::Diff by providing three-way merge and diff
functions.
In this documentation, the first list to "diff3", "merge",
and "traverse_sequences3" is called the `original' list. The second
list is the `left' list. The third list is the `right' list.
The optional key generation arguments are the same as in Algorithm::Diff. See
Algorithm::Diff for more information.
diff3¶
Given references to three lists of items, "diff3" performs a three-way
difference.
This function returns an array of operations describing how the left and right
lists differ from the original list. In scalar context, this function returns
a reference to such an array.
Perhaps an example would be useful.
Given the following three lists,
original: a b c e f h i k
left: a b d e f g i j k
right: a b c d e h i j k
merge: a b d e g i j k
we have the following result from diff3:
[ 'u', 'a', 'a', 'a' ],
[ 'u', 'b', 'b', 'b' ],
[ 'l', 'c', undef, 'c' ],
[ 'o', undef, 'd', 'd' ],
[ 'u', 'e', 'e', 'e' ],
[ 'r', 'f', 'f', undef ],
[ 'o', 'h', 'g', 'h' ],
[ 'u', 'i', 'i', 'i' ],
[ 'o', undef, 'j', 'j' ],
[ 'u', 'k', 'k', 'k' ]
The first element in each row is the array with the difference:
c - conflict (no two are the same)
l - left is different
o - original is different
r - right is different
u - unchanged
The next three elements are the lists from the original, left, and right arrays
respectively that the row refers to (in the synopsis, these are @ancestor, @a,
and @b, respectively).
merge¶
Given references to three lists of items, "merge" performs a three-way
merge. The "merge" function uses the "diff3" function to
do most of the work.
The only callback currently used is "CONFLICT" which should be a
reference to a subroutine that accepts two array references. The first array
reference is to a list of elements from the left list. The second array
reference is to a list of elements from the right list. This callback should
return a list of elements to place in the merged list in place of the
conflict.
The default "CONFLICT" callback returns the following:
q{<!-- ------ START CONFLICT ------ -->},
(@left),
q{<!-- ---------------------------- -->},
(@right),
q{<!-- ------ END CONFLICT ------ -->},
traverse_sequences3¶
This is the workhorse function that goes through the three sequences and calls
the callback functions.
The following callbacks are supported.
- NO_CHANGE
- This is called if all three sequences have the same element at the current
position. The arguments are the current positions within each sequence,
the first argument being the current position within the first
sequence.
- A_DIFF
- This is called if the first sequence is different than the other two
sequences at the current position. This callback will be called with one,
two, or three arguments.
If one argument, then only the element at the given position from the first
sequence is not in either of the other two sequences.
If two arguments, then there is no element in the first sequence that
corresponds to the elements at the given positions in the second and third
sequences.
If three arguments, then the element at the given position in the first
sequence is different than the corresponding element in the other two
sequences, but the other two sequences have corresponding elements.
- B_DIFF
- This is called if the second sequence is different than the other two
sequences at the current position. This callback will be called with one,
two, or three arguments.
If one argument, then only the element at the given position from the second
sequence is not in either of the other two sequences.
If two arguments, then there is no element in the second sequence that
corresponds to the elements at the given positions in the first and third
sequences.
If three arguments, then the element at the given position in the second
sequence is different than the corresponding element in the other two
sequences, but the other two sequences have corresponding elements.
- C_DIFF
- This is called if the third sequence is different than the other two
sequences at the current position. This callback will be called with one,
two, or three arguments.
If one argument, then only the element at the given position from the third
sequence is not in either of the other two sequences.
If two arguments, then there is no element in the third sequence that
corresponds to the elements at the given positions in the first and second
sequences.
If three arguments, then the element at the given position in the third
sequence is different than the corresponding element in the other two
sequences, but the other two sequences have corresponding elements.
- CONFLICT
- This is called if all three sequences have different elements at the
current position. The three arguments are the current positions within
each sequence.
BUGS¶
Most assuredly there are bugs. If a pattern similar to the above example does
not work, send it to <jsmith@cpan.org> or report it on
<
http://rt.cpan.org/>, the CPAN bug tracker.
Algorithm::Diff's implementation of "traverse_sequences" may not be
symmetric with respect to the input sequences if the second and third sequence
are of different lengths. Because of this, "traverse_sequences3"
will calculate the diffs of the second and third sequences as passed and
swapped. If the differences are not the same, it will issue an
`Algorithm::Diff::diff is not symmetric for second and third sequences...'
warning. It will try to handle this, but there may be some cases where it
can't.
SEE ALSO¶
Algorithm::Diff.
AUTHOR¶
James G. Smith, <jsmith@cpan.org>
COPYRIGHT¶
Copyright (C) 2003, 2007 Texas A&M University. All Rights Reserved.
This module is free software; you may redistribute it and/or modify it under the
same terms as Perl itself.