Parameter substitution

[Alan Gates <ga...@yahoo-inc.com>]

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.