tsearch2 sourcecode problem

Hello
I have been read tsearch2's source code day by day for a whole week.And some questions puzzled me a lot, will you please have a look at it and help me ?

1.the function parse() defined in wparser.c is only appeared at that place at only once when I searched for the key "parse(", in what other places does this function take effect?In my opnion , the text parsing work is done by parstext_v2() func.

2.what does the "morph parsing" (in file query line 261 mean),what's the difference between "normal" parsing?

3.polish notation postfix is requied,also a query is made in order to make to_tsquery to be the ts_query.but I really got stuck!!
will you explain the polish notation and query tree? They're relationships!!!!!!!!!!!!!!
OR the tree's internal structures
eg. what query:"book & ( pop | ( !hill & jeen) )" will turn to be in the polsih notaion and the query tree?

4.Why use crc32_sz()?I really dont' know What ' s the need?

WHIT best regards and deepest hope.

Because I want to do it in Chinese lan.

YiFengsheng