Simple counter for stages executed so far.
Simple counter for stages executed so far. Should start initially at zero and increment by one after each stage.
This is used in error handling schemes to compare how far in the pipeline the computation got before errors.
Specifically this feature is used by fi.pelam.csv.table.TableReaderEvaluator in the ordering of fi.pelam.csv.table.TableReadingErrors.
fi.pelam.csv.util.Pipeline uses this to update stage number automatically.
fi.pelam.csv.util.Pipeline uses this to update stage number automatically.
Otherwise identical object, but with stage number incremented.
This is class is an internal class used to thread state through stages in TableReader.