I have been trying to integrate GSL (Gnu Scientific Library) into an iPhone project using Xcode. The challenge is GSL has all the modules in different folders, yet when their header files are reference, they often reference instead of or . At least with I could use Xcode's recursive header file search to find it. But with , basically file not found. Does anyone have an easy way to address the hierarchical GSL structure to compile into Xcode? I can do it the tedious way of fixing all the #INCLUDE lines but hoping there is a better alternative. This way, I can more easily update GSL when changes are made by the community. NOTE: I found Xcode needs to find the right header file locations (make sure to adjust your TARGET Build settings, not just your Project Build settings).