lcs ( seq1 seq2 -- lcs )
LCS, diffing and distance

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lcs-diff ( old new -- diff )

Vocabulary
lcs

Inputs

seq1	a sequence
seq2	a sequence

Outputs

lcs	a longest common subsequence

Word description
Given two sequences, calculates a longest common subsequence between them. Note two things: this is only one of the many possible LCSs, and the LCS may not be contiguous.

Definition

USING: accessors kernel sequences ;

IN: lcs

: lcs ( seq1 seq2 -- lcs )
    [ lcs-diff [ retain? ] filter ] keep [ item>> ] swap map-as
    ;