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

• brew install comby

• bash <(curl -sL get-comby.netlify.app)

• Other Linux distributions: The PCRE library is dynamically linked in the Ubuntu binary. For other distributions like Arch Linux, a fixup is needed: sudo ln -s /usr/lib/libpcre.so /usr/lib/libpcre.so.3. On Fedora, use sudo ln -s /usr/lib64/libpcre.so /usr/lib64/libpcre.so.3. Alternatively, consider building from source.

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

• docker pull comby/comby

click to expand an example invocation for the docker image

Running with docker on stdin:

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

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.

• Install opam. TL;DR do sh <(curl -sL https://raw.githubusercontent.com/ocaml/opam/master/shell/install.sh)

• Run this if you don't have OCaml installed (it bootstraps the OCaml compiler):

opam init
opam switch create 4.11.0 4.11.0

• Run eval $(opam env)

• Install OS dependencies:

  • Linux: sudo apt-get install autoconf libpcre3-dev pkg-config zlib1g-dev m4 libgmp-dev libev4 libsqlite3-dev

  • Mac: brew install pkg-config gmp pcre libev

• Then install the library dependencies:

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

• Build and test

make
make test

• Install comby on your PATH by running

make install