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 reversed Weight type.

Usage

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

Examples

A:

reverse1.jpg

Reverse of A:

reverse2.jpg

Reverse(&A);
fstreverse a.fst out.fst

Complexity

Reverse:

  • Time: O(V + E)
  • Space: O(V + E)
where V = # of states and E = # of arcs.

-- MichaelRiley - 03 Jul 2007

Topic attachments
I Attachment History Action Size Date Who Comment
JPEGjpg reverse1.jpg r3 r2 r1 manage 14.3 K 2007-07-03 - 01:19 MichaelRiley  
JPEGjpg reverse2.jpg r3 r2 r1 manage 18.5 K 2007-07-03 - 01:19 MichaelRiley  
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Topic revision: r3 - 2018-04-27 - MichaelRiley
 
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