boost::format parse method doesn't work

[andyjoseph]

In version 1.33.1:

The method boost::format.parse() doesn't properly reset
its internal state.  The simple code block below
demonstrates this.

format fmt("one");
cout << fmt.str();

fmt.parse("two");
cout << fmt.str();

---
The output is:
oneonetwo

What's happening is the parse method seems to append
the second parsing string to the first one.