added a README

README.md

@@ -0,0 +1,35 @@
+# Lexmatch
+
+This is a simple lexicon matching tool that, given a lexicon of words or phrases, identifies all matches in a given target text.
+It can be used compute a frequency list for a lexicon, on a target corpus.
+
+The implementation uses suffix arrays. The text must be plain-text UTF-8 and is limited to 2^32 bytes (about 4GB).
+
+
+## Installation
+
+You can build and install the latest stable release using Rust's package manager:
+
+```
+cargo install lexmatch
+```
+
+or if you want the development version after cloning this repository:
+
+```
+cargo install --path .
+```
+
+No cargo/rust on your system yet? Do ``sudo apt install cargo`` on Debian/ubuntu based systems, ``brew install rust`` on mac, or use [rustup](https://rustup.rs/).
+
+## Usage
+
+See ``lexmatch --help``.
+
+Simple example:
+
+```
+$ lexmatch --lexicon lexicon.lst --text corpus.txt
+```
+
+The lexicon must be plain-text UTF-8 containing one entry per line, an entry need not be a single word and is not constrained in length.