initial

Author: codinuum

.gitignore

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+*~
+*.cmo
+*.cmi
+*.cmx
+*.cmxs
+*.cmxa
+*.annot
+*.output
+*.automaton
+*.conflicts
+*.o
+*.a
+*.d
+*.di
+*.opt
+tmp
+_build
+

README.md

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+# Diff/AST: A Fine-Grained Source Code Differencing Tool
+
+The tool is currently able to recognize Python, Java, Verilog, Fortran, and C/C++ via dedicated parsers.
+It compares abstract syntax trees (ASTs) node by node, while popular `diff` tools compare any (text) files line by line.
+The algorithm is based on [an algorithm](https://doi.org/10.1137/0218082) for computing *tree edit distance (TED)* between two ordered labeled trees.  The TED between two trees is the minimum (weighted) number of edit operations to transform one tree into another.
+Unfortunately, however, applying TED algorithms directly to wild ASTs is not feasible in general because [their computational complexity is essentially, at best, quadratic according to the number of AST nodes](https://doi.org/10.1016/j.tcs.2004.12.030).
+Therefore Diff/AST makes moderate use of a TED algorithm in a divide-and-conquer manner backed by elaborated heuristics to approximate tree edit distances.
+Nevertheless, Diff/AST still requires much time for non-trivial massive inputs. Thus it always caches the results.
+
+Diff/AST is able to export ASTs, changes between them, and other syntactic/semantic information as *facts* in
+[XML](https://www.w3.org/TR/xml11/) or [N-Triples](https://www.w3.org/2001/sw/RDFCore/ntriples/).
+In particular, facts in N-Triples format can be loaded into an RDF store such as
+[Virtuoso](https://github.com/openlink/virtuoso-opensource) to build a *factbase* or a database of facts.
+Factbases are intended to be queried for software engineering tasks such as
+[code comprehension](https://github.com/ebt-hpc/cca),
+[debugging](https://stair.center/archives/research/ddj-esecfse2018),
+[change pattern mining](https://ieeexplore.ieee.org/document/7081845), and
+[code homology analysis](https://link.springer.com/chapter/10.1007/978-3-642-12029-9_7).
+
+Diff/AST is an experimental implementation of the tree differencing algorithm
+reported in the following paper:
+
+Masatomo Hashimoto and Akira Mori, "Diff/TS: A Tool for Fine-Grained Structural Change Analysis,"
+In *Proc. 15th Working Conference on Reverse Engineering*, 2008, pp. 279-288,
+DOI: [10.1109/WCRE.2008.44](https://doi.org/10.1109/WCRE.2008.44).
+
+## Screenshots
+
+You can see the results of comparing some pairs of source files taken from [samples](samples) [here](https://codinuum.github.io/gallery-cca).
+
+## Quick start
+
+You can instantly try Diff/AST by utilizing [Docker](https://www.docker.com/) and [a ready-made container image](https://hub.docker.com/r/codinuum/diffast).
+
+    $ docker pull codinuum/diffast
+
+The following command line executes Diff/AST within a container to compare sample Java programs and then saves the results in `results` (host) directory.
+
+    $ ./cca.py diffast -c results samples/java/0/Test.java samples/java/1/Test.java
+
+Once you have built [DiffViewer](diffviewer), you can inspect the AST differences in a viewer window. See [`diffviewer/README.md`](diffviewer/README.md) for details.
+
+    $ diffviewer/run.py -c results samples/java/0/Test.java samples/java/1/Test.java
+
+You can run both Diff/AST and DiffViewer by the following line.
+
+    $ ./cca.py diffast -c results --view samples/java/0/Test.java samples/java/1/Test.java
+
+## Installing parsers and Diff/AST
+
+### Requirements
+
+* [OCaml](http://ocaml.org/) (>=4.14)
+* [OPAM](https://opam.ocaml.org/)
+
+### Installation
+
+The following will install `parsesrc` and `diffast`.
+
+    $ opam install diffast
+
+## Building parsers and Diff/AST
+
+You can also build parsers and Diff/AST in person.
+
+### Requirements
+
+* [OCaml](http://ocaml.org/) (>=4.14)
+* [Dune](https://github.com/ocaml/dune)
+* [OPAM](https://opam.ocaml.org/) (for installing bytesrw, camlzip, cryptokit, csv, git-unix, markup, menhir, sedlex, uuidm, and vlt.)
+
+### Compilation
+
+The following will create `./dist/bin/{parsesrc,diffast}`.
+
+    $ dune build --relocatable --prefix ./dist
+
+## Using with Git
+
+If you have built Diff/AST, you can use it with Git. Add the following lines to your `.gitconfig`. Note that `PATH_TO_THIS_REPO` should be replaced by your local path to this repository.
+
+    [diff]
+        tool = diffast
+    [difftool]
+        prompt = false
+    [difftool "diffast"]
+        cmd = PATH_TO_THIS_REPO/git_ext_diff "$LOCAL" "$REMOTE"
+    [alias]
+        diffast = difftool
+
+Then you should be able to use `git diffast` like `git diff`. You will be prompted to launch diffast for each source file comparison. Other file comparisons will be ignored.
+
+
+## Building docker image
+
+The following command line creates a docker image named `diffast`.
+
+    $ docker build -t diffast .
+
+## License
+
+Apache License, Version 2.0