http://wiki.apache.org/pig/ParameterSubstitution
What if instead we just built a C style preprocessor exactly, with #define, #include, #ifdef, #ifndef, #if, #else, and #endif?
This would meet requirements 1, 2, 3, 5, and 6. For 4, people would have to generate the values with a script or binary themselves before calling the command line, but this should be trivial: pig -Dbla=`xxx`
This has the advantage that it is well understood by all, implementers and users. No one has to develop a new set or semantics and we don't have to deal with user questions of how it works.
Alan.
