(r7) IntersectDoc < FST

FST Web>FstQuickTour>IntersectDoc (revision 7) (raw view)~~EditAttach~~

---+ Intersect

---++ Description

This operation computes the intersection (Hadamard product) of two FSAs. Only strings that are in 
both automata are retained in the result.

The two arguments must be [[FstGlossary#AcceptorDef][acceptors]].
One of the arguments must be [[ArcSortDoc][label-sorted]] (or otherwise support an appropriate [[FstQuickTour#FstMatcher][matcher]]).The weights need to form a [[FstWeightRequirements][commutative semiring]] (valid for =TropicalWeight= and =LogWeight= for instance).

Versions of this operation (not all shown here) accept [[FstAdvancedUsage#FstOptions][options]] that allow choosing the [[FstAdvancedUsage#FstMatchers][matcher]], [[FstAdvancedUsage#Composition_Filters][composition filter]], [[FstAdvancedUsage#State_Tables][state table]] and, when delayed, the [[FstAdvancedUsage#FstCaching][caching behaviour]] used by intersection. 

---++ Usage

|<verbatim>
template <class Arc> 
void Intersect(const Fst<Arc> &ifsa1, const Fst<Arc> &ifsa2, MutableFst<Arc> *ofsa);
</verbatim>| %DOX{namespacefst.html#Intersect[%H%]}% |
|<verbatim>
template <class Arc> IntersectFst<Arc>::
IntersectFst(const Fst<Arc> &fsa1, const Fst<Arc> &fsa2);
</verbatim>| %DOX{fst::IntersectFst[%H%]}% |
|<verbatim>
fstintersect [--opts] a.fsa b.fsa out.fsa
  --connect: Trim output (def: true)
</verbatim> | |

---++ Examples

---+++ =A=:

%ATTACHURL%/intersect1.jpg

---+++ =B=:

%ATTACHURL%/intersect2.jpg

---+++ =A &cap; B=:

%ATTACHURL%/intersect3.jpg

<verbatim>
Intersect(A, B, &C);
IntersectFst<Arc>(A, B);
fstintersect a.fsa b.fsa out.fsa
</verbatim>

---++ Complexity

Same as _[[ComposeDoc#ComposeComplexity][Compose]]_.

---++ Caveats

Same as _[[ComposeDoc#ComposeCaveats][Compose]]_.

---++ See Also

 [[FstAdvancedUsage#ComposeFilters][Composition Filters]], [[FstAdvancedUsage#FstMatchers][Matchers]], [[FstAdvancedUsage#StateTables][State Tables]]


-- Main.MichaelRiley - 30 Jun 2007

Attachments

Topic attachments
I	Attachment	History	Action	Size	Date	Who
jpg	intersect1.jpg	r3 r2 r1	manage	11.0 K	2007-06-30 - 21:59	MichaelRiley
jpg	intersect2.jpg	r2 r1	manage	10.4 K	2007-06-30 - 21:59	MichaelRiley
jpg	intersect3.jpg	r2 r1	manage	13.9 K	2007-06-30 - 22:00	MichaelRiley

Topic revision: r7 - 2014-04-23 - MichaelRiley