# experimental/diff

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This module implements an algorithm to compute the diff between two sequences of lines.

- To learn more see Diff on Wikipedia.

Example:

    import experimental/diff
    assert diffInt(
      [0, 1, 2, 3, 4, 5, 6, 7, 8],
      [-1, 1, 2, 3, 4, 5, 666, 7, 42]) ==
      @[Item(startA: 0, startB: 0, deletedA: 1, insertedB: 1),
        Item(startA: 6, startB: 6, deletedA: 1, insertedB: 1),
        Item(startA: 8, startB: 8, deletedA: 1, insertedB: 1)]

Example:

    import experimental/diff
    # 2 samples of text (from "The Call of Cthulhu" by Lovecraft)
    let txt0 = """
    abc
    def ghi
    jkl2"""
    let txt1 = """
    bacx
    abc
    def ghi
    jkl"""
    assert diffText(txt0, txt1) ==
      @[Item(startA: 0, startB: 0, deletedA: 0, insertedB: 1),
        Item(startA: 2, startB: 3, deletedA: 1, insertedB: 1)]

# Imports

tables, strutils

# Types

    Item = object
      startA*: int               ## Start Line number in Data A.
      startB*: int               ## Start Line number in Data B.
      deletedA*: int             ## Number of changes in Data A.
      insertedB*: int            ## Number of changes in Data B.

  An Item in the list of differences. Source Edit

# Procs

    proc diffInt(arrayA, arrayB: openArray[int]): seq[Item] {....raises: [], tags: [],
        forbids: [].}

  Find the difference in 2 arrays of integers.

  `arrayA` A-version of the numbers (usually the old one)

  `arrayB` B-version of the numbers (usually the new one)

  Returns a sequence of Items that describe the differences.

  Source Edit

    proc diffText(textA, textB: string): seq[Item] {....raises: [KeyError], tags: [],
        forbids: [].}

  Find the difference in 2 text documents, comparing by textlines.

  The algorithm itself is comparing 2 arrays of numbers so when comparing 2 text documents each line is converted into a (hash) number. This hash-value is computed by storing all textlines into a common hashtable so i can find duplicates in there, and generating a new number each time a new textline is inserted.

  `textA` A-version of the text (usually the old one)

  `textB` B-version of the text (usually the new one)

  Returns a seq of Items that describe the differences.

  Source Edit