Welcome to Spirit

Spirit is a set of C++ libraries for parsing and output generation implemented as Domain Specific Embedded Languages (DSEL) using Expression templates and Template Meta-Programming. The Spirit libraries enable a target grammar to be written exclusively in C++. Inline grammar specifications can mix freely with other C++ code and, thanks to the generative power of C++ templates, are immediately executable.

Spirit is part of Boost Libraries, a peer-reviewed, open collaborative development effort.

Jul ’11 23

Mike Lewis posted a marvelous experience report dubbed ‘Optimizing Boost Spirit – Blazing fast AST generation using boost::spirit’. He describes how he took an old compiler for the Epoch programming language (which was based on Spirit.Classic) and tuned it for performance using Spirit.Qi and Spirit.Lex. His results are exceptional, he got roughly a thousand fold speedup compared to the old version. The complete code for his compiler can be downloaded from here.

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Jul ’11 12

Spirit V2.5 is now available as part of the recently released Boost V1.47. I suggest you look at the What’s New documentation page for a list of things changed. This is a very important release for Spirit, mostly in the area of feature consolidation and less so by adding new functionality. It brings a lot of unification and quite some speedup in the area of attribute handling, both for parsers (Qi) and generators (Karma). Most of the newly added features are in the area of unification of the overall user experience as well. The things added to the Lexer should finally resolve some long standing requests. Most importantly, we are very excited about having added full compatibility with the newly released Phoenix V3 library.

Generally, all changes are supposed to be fully backwards compatible. If you run into problems with your existing code, please tell us by leaving a comment or by sending a message to the Spirit mailing list (as described on our Support page).

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Feb ’11 26

Frank Dellaert was asking a valid question on the Spirit mailing list where he pointed out some things he was not able to understand. His question clearly uncovered an inconsistency in Spirit’s API. This lead us to implement some minor additional feature, which in the end turned out to make more uniform the way semantic actions are handled.

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Feb ’11 12

Narinder Claire asked a seemingly innocent question on the Spirit mailing list the other day. After starting to write an answer I realized that this question is not innocent at all as it touches the very fabric of Spirit: the rules of attribute handling. Many people have a hard time to properly understand what is going on in the nether regions of Spirit. More importantly, they have a hard time to understand why is Spirit implemented the way it is.

The new article Attribute Propagation and Attribute Compatibility not only answers Narinders questions but tries to explain those important concepts in more detail.

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Dec ’10 03

These are links to the slides and video of Michael Caisse’s BoostCon 2010 talk:

slides: <http://www.objectmodelingdesigns.com/boostcon10/>
video: <http://blip.tv/file/4143337 >

Enjoy!

Machinery, sensors, equipment, client/server communications, even file formats… Parsing and producing communication streams is everywhere you look. Often these tasks are simple or small enough to tempt ad-hoc solutions. The Spirit 2.1 library provides a model that is simple enough to tackle those “quick hacks” and easily scales for full-featured AST generation.

This session will explore real-life experiences with the parser and generator (Qi/Karma) portions of the Spirit library. As we look at various small and medium-sized parsers/generators employed in various products we will establish some “rules-of-thumb” and guidelines for tackling the parser/generator domain with Qi/Karma. The session will end with the implementation of a usable XML parser and a simplified XPath-like node extractor.

The session will include some lecture and a lot of tutorial. Attendees will walk away with the knowledge and tools to begin parsing and generating with Spirit Qi/Karma.

—Michael Caisse

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Nov ’10 13

Jeroen Habraken (a.k.a VeXocide) sent an article about parsing escaped strings using Qi, which we happily publish for everybody to read. Thanks Jeroen!

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Nov ’10 07

The Spirit mailing list is still the place where active discussion takes place. I will be posting some excerpts from the mailing list here every once in a while. Here’s an interesting post from Leo Goodstadt:
Are Qi parsers thread-safe?

The answer of course is yes

I have been trying to speed up some parsing code going through around 25 GB of data. This had been taking up 6 hours using Python code. Re-writing it using Qi had taken it down to 4 minutes. And finally, with the help of Intel Threading Building Blocks, I am down to 37 seconds or a > 500x speedup!
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May ’10 13

Michael Caisse (of Object Modeling Designs), some of you will know him from the Freenode #boost IRC channel, presented his talk about Spirit at BoostCon 2010 last Tuesday. I personally very much like listening to his knowledgeable and entertaining presentations. Apparently many people do so as well, the room he presented in was overfull. People even sat on the floor as all seats were taken. So in case you are interested – here is a link to his slides: Using Spirit V2: Qi and Karma.

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May ’10 11

Finally, yesterday was the day! Joel and I presented the current status of our work related to the ‘Writing a Compiler’ effort. We submitted this talk to BoostCon 2010 and got accepted back in January. Having to present at BoostCon just put a nice pressure onto us to get moving and to start working on the project. I don’t want to go into any detail about the presentation itself. This will be done in future articles to be published after BoostCon. I just wanted to provide a link to the slides for those interested in having a look. Ok, here we go: A Framework for RAD Spirit, grab it while it’s hot!

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May ’10 08

Finally, the long wait and the preparations for BoostCon 2010 are over. The last weeks were dominated by writing the code and creating the slides for our talk ‘A Framework for RAD Spirit‘. Regular readers of this site probably have already wondered why we have been inactive here since mid-March. Well, that is mainly because of preparing for BoostCon turned out to be too time consuming to leave any room for writing posts and articles.

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Mar ’10 05

Tracking the Input Position While Parsing

By Peter Schüller Advanced, Beginner, Qi Example Comments Off on Tracking the Input Position While Parsing

The following article is about tracking the parsing position with Spirit V2. This is useful for generating error messages which tell the user exactly where an error has occurred. We also show how to use Spirit V2 to parse from an input stream without first reading the whole stream into a std::string.

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Mar ’10 03

The concept of Spirit’s semantic actions seems to be easy enough to understand as most people new to the library prefer their usage over applying the built-in attribute propagation rules. That is not surprising. The idea of attaching a function to any point of a grammar which is called whenever the corresponding parser matched is straighforward to grasp. Earlier versions of Spirit required a semantic action to conform to a very specific interface. Today’s semantic actions are more flexible and more powerful. Recently, a couple of people asked questions about them. So I decided dedicating this Tip of the Day to the specifics and the usage model of semantic actions in Spirit Qi.

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Feb ’10 24

Spirit supports skipper based parsing since its very invention. So this is definitely not something new to Spirit V2. Nevertheless, the recent discussion on the Spirit mailing list around the semantics of Qi’s lexeme[] directive shows the need for some clarification. Today I try to answer questions like: “What does it mean to use a skipper while parsing?”, or “When do I want to use a skipper and when not?”.

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Feb ’10 17

Recently, there have been a couple of questions on the Spirit mailing list asking how to parse as set of things known in advance in any sequence and any combination. A simple example would be a list of key/value pairs with known keys but the keys may be ordered in any sequence. This use case seems to be quite common. Fortunately Spirit provides you with a predefined parser component designed for exactly that purpose: the permutation parser.

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Feb ’10 08

Here is another question raised from time to time: “I know how to use a plain struct as an attribute for a sequence parser in Qi by adapting it with BOOST_FUSION_ADAPT_STRUCT. Unfortunately this does not work if the struct is a template. What can I do in this case?”.

There have been plans for a while to create a separate Fusion facility BOOST_FUSION_ADAPT_TPL_STRUCT allowing to adapt templated data types, but this is not in place yet. Today I will describe a trick you can apply to adapt your templates into ‘proper’ Fusion sequences anyway.

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