One of the many, many legitimate criticisms that could be leveled at C++ is that string handling is abysmal. Sure std::string can hold some chars for you, but there is a distinct lack of utility functions to actually do anything with those characters. Enter the Boost String Algorithm library, or string_algo to its many friends.

String_algo contains all those fiddly little functions that you write yourself to process text, as well as some clever extensions. The simple stuff is very simple:

The is_punct() function returns a predicate – string_algo defines a bunch of useful predicates so you will rarely have to roll your own. Not shown in the above is the ability to pass a std::locale to handle strings in other languages.

There is the full compliment of find, replace, and erase substring options:

(the -2 parameter for replace_nth means “replace the 2nd from last occurance” – very useful)

And check this out:

I haven’t even mentioned the ability to do fancy things with regular expression and the concept of find iterators that advance over the substrings that match. Also, the library is generic enough to work with any container that looks vaguely like a sequence of characters, not just std::string.

String_algo is replacing vast numbers of little hacked-together functions in my code. If nothing else it will reduce the temptation to use the God-forsaken CString classes.

We are still only in the low lands of boost territory but already we are coming across useful discoveries. Today’s stop is boost::assign, one of those clever little pieces of code that makes life easier for everyone. Often you just want to load up a container with some small amount of data. The STL containers do not make such a task particularly easy:

What a pain in the neck! With boost::assign it becomes:

Neat.

It gets better. A lot of the time you want to fill a container with some data for testing but you don’t really care what that data is:

Or even:

Of course, other containers are supported. This example uses the more flexible insert function (there are other functions for inserting at specific points for containers that support such things):

As with all the boost libraries, a lot of thought has gone into to making the interface safe and flexible. The library can even be extended to non-standard containers if the need should arise.

All the best magic tricks are really just smoke and mirrors, boost::assign is really just functions that secretly return functor objects and operator,() abuse. Unlike most magic, knowing how it works makes it even more delightful; the library is very well documented.

Although boost::assign is useful anywhere, it really shines in simple throwaway programs and test harnesses, where small, simple and easily modifiable code is the goal. I keep finding more and more places to use it.