clean directories before installing headers

[lorenz@…]

The make install target should clean out some directories before installing, maybe there is even an automake option to do that?

Recently stairc.h was moved from GBEngine to combinatorics but installing the updated source to the same prefix preserves the old header:

$ find prefix-singular-test/ -name stairc.h
prefix-singular-test/include/singular/kernel/combinatorics/stairc.h
prefix-singular-test/include/singular/kernel/GBEngine/stairc.h

Because of this we did not notice that we had to update our interface. And code using libsingular might still use the old header but the new library which could be incompatible.

[hannes]

"make uninstall" does this: it clean all files "make install" installed.

Include: you should include libsingular.h (instead of single internal files) which takes care of changes in the interface.