lex

Overview

Package lex provides the core of a lexer built as a Deterministic Finite State Automaton whose states and associated actions are implemented as functions.

Clients of the package only need to provide state functions specialized in lexing the target language. The package provides facilities to stream input from a io.Reader with up to 15 bytes look-ahead, as well as utility functions commonly used in lexers.

The implementation is similar to https://golang.org/src/text/template/parse/lex.go. See also Rob Pike's talk about combining states and actions into state functions: https://talks.golang.org/2011/lex.slide.

Read the full package ducumentation on gpkg.go.dev.

Release notes

v1.2.1

Improvements to error handling:

Lexer.Errorf now generates error values instead of string. lexer.Emit enforces the use of error values for Error tokens.

Scanner now implements the io.RuneScanner interface.

This is a minor API breakage that does not impact any known client code.

v1.0.0

Initial release.

License

Package lex is released under the terms of the MIT license:

Copyright 2017-2020 Denis Bernard db047h@gmail.com

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.