Text.Regex.TDFA.TNFA converts the CorePattern Q/P data (and its
Pattern leafs) to a QNFA tagged non-deterministic finite automata.
This holds every possible way to follow one state by another, while
in the DFA these will be reduced by picking a single best
transition for each (soure,destination) pair. The transitions are
heavily and often redundantly annotated with tasks to perform, and
this redundancy is reduced when picking the best transition. So
far, keeping all this information has helped fix bugs in both the
design and implementation.
The QNFA for a Pattern with a starTraned Q/P form with N one
character accepting leaves has at most N+1 nodes. These nodes
repesent the future choices after accepting a leaf. The processing
of Or nodes often reduces this number by sharing at the end of the
different paths. Turning off capturing while compiling the pattern
may (future extension) reduce this further for some patterns by
processing Star with optimizations. This compact design also means
that tags are assigned not just to be updated before taking a
transition (PreUpdate) but also after the transition (PostUpdate).
Uses recursive do notation.
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Instances