ReverseDoc < FST

---+ Reverse

---++ Description
This operation reverses an FST. If =A= transduces string =x= to =y= with weight =a=,
then the reverse of =A= transduces the reverse of =x= to the reverse of =y= with weight =a.Reverse()=.

Typically, =a= = =a.Reverse()= and =Arc= = =RevArc= (e.g. for
=TropicalWeight= or =LogWeight=).  In general, e.g., when the weights
only form a left or right semiring, the output arc type must match
the input arc type except having the [[FstWeightRequirements][reversed Weight type]].

---++ Usage
|<verbatim>
template<class Arc, class RevArc>
void Reverse(const Fst<Arc> &ifst, MutableFst<RevArc> *ofst);
</verbatim>| 
|<verbatim>
fstreverse a.fst out.fst
</verbatim> | 

---++ Examples

---+++ =A=:

%ATTACHURL%/reverse1.jpg

---+++ =Reverse of A=:

%ATTACHURL%/reverse2.jpg

<verbatim>
Reverse(&A);
fstreverse a.fst out.fst
</verbatim>

---++ Complexity

=Reverse=:
   * Time: _O(V + E)_
   * Space: _O(V + E)_ %BR%
where _V_ = # of states and _E_ = # of arcs.

-- Main.MichaelRiley - 03 Jul 2007

Attachments

Topic attachments
I	Attachment	History	Action	Size	Date	Who	Comment
jpg	reverse1.jpg	r3 r2 r1	manage	14.3 K	2007-07-03 - 01:19	MichaelRiley
jpg	reverse2.jpg	r3 r2 r1	manage	18.5 K	2007-07-03 - 01:19	MichaelRiley

This topic: FST > WebHome > FstQuickTour > ReverseDoc
Topic revision: r3 - 2018-04-27 - MichaelRiley