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:

Reverse of A:

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