4.2 Language Requirements

I set forth the following requirements for the FiST language:

• The language should be portable across different operating systems offering the vnode interface, and accommodate small differences in vnode interface implementations.

• The language should have a familiar ``look and feel.'' A model like that used by yacc is desirable.

• No tedious or repetitive tasks should be required. Every option that can be automated or defaulted should be.

• There should be keywords that can alter the overall behavior of the generated code. Hopefully, this would make it easy to write a FiST program by altering a working FiST program for a different type of file system.

• On the other hand, the advanced ``hacker'' should not be left out. There should be facilities to modify or augment the behavior of every vnode operation, from simple keywords all the way to hand-writing C code.

• The language should be as high a level as possible while retaining flexibility to adjust small details and ease of parsing.

• An empty input file should result in a usable file system, in particular the wrapper file system, described in Appendix sec-appendix-typical-in-core-wrapfs.