XML — Architecture, Tools, Techniques - Department of Computer ...

Handler is a GoalMakerFactory which constructs a single Trace object. shift() verifies
that there is only a single observer. The trace of 3+4*5 suggests that it could be converted into
an expression tree:
$ java -classpath .:oops.jar oops.Compile -f Handler expr.ser Scanner > /dev/null
GoalMakerFactory is Handler
3+4*5
handler shift Number 3
handler reduce 3
handler shift handler reduced
handler reduce 3 [reduced]
handler shift handler reduced
handler shift "+" +
handler shift Number 4
handler reduce 3 [reduced] [reduced] + 4
handler shift handler reduced
handler shift "*" *
handler shift Number 5
handler reduce 3 [reduced] [reduced] + 4 [reduced] * 5
handler shift handler reduced
handler reduce 3 [reduced] [reduced] + 4 [reduced] * 5 [reduced]
handler shift handler reduced
handler reduce 3 [reduced] [reduced] + 4 [reduced] * 5 [reduced] [reduced]
handler shift handler reduced
handler shift "\n" null
handler shift "\n" null
handler reduce 3 [reduced] [reduced] + 4 [reduced] * 5 [reduced] [reduced] [reduced]
The additional \n is synthesized by the scanner (which otherwise would have to read ahead).
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