sluongng / comby

A tool for structural code search and replace that supports ~every language.

comby

See the usage documentation.

A short example below shows how comby simplifies matching and rewriting compared to regex approaches like sed.

Need help writing patterns or have other problems? Consider posting in Gitter.

Install (pre-built binaries)

Mac OS X

• brew install comby

Ubuntu Linux

• bash <(curl -sL get.comby.dev)

• Arch and other Linux: The PCRE library is dynamically linked in the Ubuntu binary. For other distributions, like Arch, a fixup is needed: ln -s /usr/lib/libpcre.so /usr/lib/libpcre.so.3. Alternatively, consider building from source.

Windows

• Install the Windows Subsystem for Linux and install Ubuntu. Then run bash <(curl -sL get.comby.dev)

Docker

• docker pull comby/comby

click to expand an example invocation for the docker image

Running with docker on stdin:

echo '(👋 hi)' | docker run -a stdin -a stdout -i comby/comby '(:[emoji] hi)' 'bye :[emoji]' lisp -stdin

Or try it live.

Isn't a regex approach like sed good enough?

Sometimes, yes. But often, small changes and refactorings are complicated by nested expressions, comments, or strings. Consider the following C-like snippet. Say the challenge is to rewrite the two if conditions to the value 1. Can you write a regular expression that matches the contents of the two if condition expressions, and only those two? Feel free to share your pattern with @rvtond on Twitter.

if (fgets(line, 128, file_pointer) == Null) // 1) if (...) returns 0
      return 0;
...
if (scanf("%d) %d", &x, &y) == 2) // 2) if (scanf("%d) %d", &x, &y) == 2) returns 0
      return 0; 

To match these with comby, all you need to write is if (:[condition]), and specify one flag that this language is C-like. The replacement is if (1). See the live example.

Build from source

• Install opam

• Create a new switch if you don't have OCaml installed:

opam init
opam switch create 4.09.0 4.09.0

• Install OS dependencies:

  • Linux: sudo apt-get install pkg-config libpcre3-dev

  • Mac: brew install pkg-config pcre

• Then install the library dependencies:

git clone https://github.com/comby-tools/comby
cd comby && opam install . --deps-only -y

• Build and test

make
make test

• If you want to install comby on your PATH, run

make install