This describes classes for iterating over paths in an FST.

`fst::PathIterator`

This template class provides a basic iterator over paths. It is constructed from
a `const Fst`

and an optional argument that specifies whether or not the
FST should be checked for acyclicity during construction.

The `ILabels()`

and `OLabels()`

methods return vectors of input and output
labels (respectively) of the current path, and the `Weight()`

method returns the
weight of the current path.

This iterator:

- is advanced using the
`Next()`

method, - is exhausted once the
`Done()`

returns`true`

, - is reset using the
`Reset()`

method, and - signals an error using the
`Error()`

method.

The acyclity check should only be disabled when the caller can ensure finite iteration (e.g., by knowing the FST is acyclic, or limiting the number of iterated paths).

`fst::StringPathIterator`

This template class is a thin wrapper around `fst::PathIterator`

which adds
`IString()`

and `OString()`

methods returning input and output strings. These
methods use the same string printing methods as `fst::PrintString`

and the
printing mode is controlled by the enum `fst::StringTokenType`

(see here for more information).

At construction time, users specify printing modes and/or symbol tables for the input and output sides of the FST, and whether or not the FST should be checked for acyclity.

This iterator:

- is advanced using the
`Next()`

method, - is exhausted once the
`Done()`

returns`true`

, - is reset using the
`Reset()`

method, and - signals an error using the
`Error()`

method.

The acyclity check should only be disabled when the caller can ensure finite iteration (e.g., by knowing the FST is acyclic, or limiting the number of iterated paths).

`pynini.StringPathIterator`

Pynini wraps `fst::script::StringPathIteratorClass`

with the Python class `StringPathIterator`

. As in C++, this object can be constructed directly from an FST argument, or it can be constructed using the `paths()`

method of an (acyclic)
`pynini.Fst`

instance.

Both construction methods take token types for both input- and output sides; for
the `SYMBOL`

token type, simply provide a `pynini.SymbolTable`

argument.

This class provides the normal iterator methods (`next()`

, `done()`

, `reset()`

,
and `error()`

), the accessor methods (`ilabels()`

, `istring()`

, `olabels()`

,
`ostring()`

, `weight()`

), and speciality iterators (`istrings()`

, `ostrings()`

, and
`weights()`

; `items()`

returns triples of input string, output string, and
weight).

Topic revision: r5 - 2018-10-16 - KyleGorman

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