hashNext

Function

hashNext

Computes the hash value for the adjacent shape.

Overlapping q-grams can efficiently be hashed by calling hash on the first text position and hashNext on succeeding, adjacent positions. Alternatively, hashInit can be used to replace the first hash call by another hashNext call and hence ease loops iterating all overlapping q-grams.

hashNext(shape, it)

Include Headers

seqan/index.h

Parameters

shape	Shape to be used for hashing. Types: Shape
it	Sequence iterator pointing to the first character of the adjacent shape.

Remarks

hash has to be called before.

Return Values

Hash value of the q-gram.

Member of

Shape

Examples

Hash loop example that outputs the hash values of all overlapping 3-grams using hash and hashNext.

File "shape_hash_next.cpp"

1	#include <seqan/sequence.h>
2	#include <seqan/index.h>
3
4	using namespace seqan;
5
6	int main ()
7	{
8	DnaString text = "AAAACACAGTTTGA";
9	Shape<Dna, UngappedShape<3> > myShape;
10
11	// output the hash value of all overlapping 3-grams
12	std::cout << hash(myShape, begin(text));
13	for (unsigned i = 1; i < length(text) - length(myShape) + 1; ++i)
14	std::cout << '\t' << hashNext(myShape, begin(text) + i);
15
16	return 0;
17	}

The overlapping hash values are:

0 0 1 4 17 4 18 11 47 63 62 56