I know lot of density functional packages in fortran, including one which we are developing in our group (Fireball-DFT) but I don't like fortran very much and I would like something which is easier to integrate to other software.
For example, I have idea to create some simple interactive tool with GUI based on DFT or semi-empirical quantum chemistry method which can provide rough results (e.g. molecular orbitals) in almost real time (for small molecules).
Although some fortran based DFT packages can be interfaced into python interface e.g. in ASE it is quite slow and cumbersome way. Also I search for solver which is minimalistic and intendend for small systems, therefeore e.g. GPAW which is largely in C/C++ is not very good for me.
Do you know some simple quantum solver written in C/C++ or even better OpenCL? In case, I consider start to develop something similar by myself.