sedlex is a lexer generator for OCaml, similar to ocamllex, but
supporting Unicode. Contrary to ocamllex, lexer specifications for
sedlex are embedded in regular OCaml source files.

The lexers work with a new kind of "lexbuf", similar to ocamllex
Lexing lexbufs, but designed to support Unicode, and abstracting
from a specific encoding. A single lexer can work with arbitrary
encodings of the input stream.

sedlex is the successor of the ulex project. Contrary to ulex which
was implemented as a Camlp4 syntax extension, sedlex is based on
the new "-ppx" technology of OCaml, which allow rewriting OCaml
parse trees through external rewriters. (And what a better name
than "sed" for a rewriter?)

As any -ppx rewriter, sedlex does not touch the concrete syntax of
the language: lexer specifications are written in source file which
comply with the standard grammar of OCaml programs. sedlex reuse
the syntax for pattern matching in order to describe lexers (regular
expressions are encoded within OCaml patterns). A nice consequence
is that your editor (vi, emacs, ...) won't get confused (indentation,
coloring) and you don't need to learn new priority rules. Moreover,
sedlex is compatible with any front-end parsing technology: it
works fine even if you use camlp4 or camlp5, with the standard or
revised syntax.