Eva
Eva is an expression evaluator developed as a cross platform utility. It is written using ANTLR(targetting C), gcc. Eva supports all C expressions including bitwise operations. It is created to aid developers to convert between hexa to binary operations easily. The main goal was very simple code base ~1000 lines.
The UI part was initially coded using wxWidgets and now contains – simple command line interface, wxWidgets and Windows specific GUI interface. Here is a video demonstrating different operations possible with Eva.
http://www.youtube.com/watch?v=m7ieVDEkdZ4
Here is the source code – https://bitbucket.org/samueldotj/eva