In order to reduce compile times I have decided to rewrite the parser/grammar from classic to spirit qi (spirit 2.1). My understanding is that faster compiles come from easier modularisation available under spirit qi. (As shown in mini_c example, in the boost tree) However I need this to be portable to as many platforms as possible. In my case minimum set is Linux,HP-UX, AIX. So my fall-back is boost 1.38. So how much has boost spirit qi changed between 1.38 and present ? How are defects reported against spirit qi, integrated back to past releases, or is there any recommended patch type mechanism, that supports redistribution of my local boost tree. Or is simply better to use spirit independently from boost? Are there any issues/guidelines that people have found in transitioning from classic to Qi. In my case I made heavy use of closures. I have not seen closures in any of spirit qi examples, Assuming there is equivalent functionality to closures ? I would interested in any recommendations before starting on this project. Best regards, Ta, Avi