Weiqi Gao's Observations - boost tag

A Little C++ To Boost Your Spirit

Wed, 26 Mar 2008 16:08:21 GMT

Take a look at the following snippet of valid C++ code ...

group = '(' >> expr >> ')';
fact = integer | group;
term = fact >> *( ('*' >> fact) | ('/' >> fact) );
expr = term >> *( ('+' >> term) | ('-' >> term) );

... and tell me C++ is not the perfect language for DSLs! ;=)

Seriously, I copied down the above from Adam Mitz's OCI internal C++ lunch talk about Boost.Spirit yesterday.

Boost.Spirit documentation: Spirit is an object-oriented recursive-descent parser generator framework implemented using template meta-programming techniques. Expression templates allow us to approximate the syntax of Extended Backus-Normal Form (EBNF) completely in C++.

The Spirit framework enables a target grammar to be written exclusively in C++. Inline EBNF grammar specifications can mix freely with other C++ code and, thanks to the generative power of C++ templates, are immediately executable. In retrospect, conventional compiler-compilers or parser-generators have to perform an additional translation step from the source EBNF code to C or C++ code.

As parser generators go, Boost.Spirit is pretty powerful stuff. As an example, Adam redid Mark Volkmann's Math example from the ANTLR 3 talk, ASTs and all.

Geeky as Boost.Spirit may seem, can think of one occasion in past projects where we could have used it instead of coding a recursive descent parser by hand.

Quote Of The Day

Wed, 27 Jun 2007 14:31:50 GMT

Eric Niebler: [...] I drift back into the real world and hear this gem from Jeff as he compares ASIO to the popular ACE library: "ACE is an open source project, so you’re free to download it, look at the source code, and be horrified."

Boost Multi-index Container

Tue, 28 Mar 2006 19:07:05 GMT

This is my second attempt at live blogging. I'm at the OCI internal C++ lunch presentation. Today's speaker is Jonathan Pollack and he's talking about the Boost multi-index container, a C++ library that solves the "data" problem in certain situations:

You have a set of data, and you would like to find them by different sets of attributes. Find Customer by SSN, by name, etc.

I'll try something different this time. I'll try to write some code as I follow the presentation.

struct Customer {
  std::string ssn_;
  std::string name_;
};
struct SSN { /* tag for an index */ };
struct Name { /* tag for an index */ };

typedef boost::multi_index_container<
  Customer,
  boost::multi_index::indexed_by<
    boost::multi_index::ordered_unique<
      boost::multi_index::tag<SSN>,
      boost::multi_index::member<Customer, std::string, &Customer::ssn_>
    >,
    boost::multi_index::ordered_non_unique<
      boost::multi_index::tag<Name>,
      boost::multi_index::member<Customer, std::string, &Customer::name_>
  >
MyCustomerDB;

typedef MyCustomerDB::index<SSN>::type SSNIndex;
typedef MyCustomerDB::index<Name>::type NameIndex;
typedef SSNIndex::iterator SSNIterator;
typedef NameIndex::iterator NameIterator;

MyCustomerDB db;
SSNIndex& ssnIndex = db.index<SSN>();
NameIndex& nameIndex = db.index<Name>();

Customer c1("333-44-5555", "John Smith");
Customer c2("666-77-8888", "Robert Brown");

db.insert(c1);
db.insert(c2);

SSNIterator ssnIter = ssnIndex.find("333-44-5555");
c1.ssn = "999-00-1111";
indexBy.replace(ssnIter, c1);