A simple diff algorithm for Nim, similar to Ratcliff-Metzener.
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A Nim implementaion of a simple diff algorithm, based on Paul Butler's simplediff.


simplediff provides a diff proc which takes two openArrays and generates a seq of "instructions" to turn the first into the second. Each "instruction" is of the Diff type, which is either an Insertion, a Deletion, or a NoChange. Each Diff also has a tokens field, which contains a subsequence of elements that the insertion/deletion/leaving alone should be applied to.

For example:

import simplediff

echo diff([1, 2, 3], [1, 2])
# @[Diff(kind: NoChange, tokens: @[1, 2]), Diff(kind: Deletion, tokens: @[3])]

Any type that implements the == operator can be used.

simplediff also provides a convenience wrapper for diffing two strings. By default, the strings are split into lines for diffing, but this can be changed with the seps parameter.

import simplediff

for diff in stringDiff("the word is blue", "the word is red", seps={' '}):
  echo diff
# Diff(kind: NoChange, tokens: @["the", "word", "is"])
# Diff(kind: Deletion, tokens: @["blue"])
# Diff(kind: Insertion, tokens: @["red"])

Other convenience wrappers may be added in the future! Feel free to request one or submit a patch.

simplediff also provides prettyDiff, which writes a formatted version of the diff to an output stream. It can be called directly or, if you need more flexibility than it offers, used as a starting point for building your own output.

See the when isMainModule block within simplediff.nim for an example of a simple diff application.


Contributions are welcome! Please send patches, questions, requests, etc. to my public inbox.