[DOC] clarification how shapes are applied in kmer-hash

seqan · May 16, 2022 · 705a777 · 705a777
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diff --git a/include/seqan3/search/views/kmer_hash.hpp b/include/seqan3/search/views/kmer_hash.hpp
@@ -774,6 +774,9 @@ namespace seqan3::views
  *
  * See the \link views views submodule documentation \endlink for detailed descriptions of the view properties.
  *
+ * \attention The Shape is defined is from right to left. The mask 0b1101 applied to ACGT will return
+ * the sequence AGT.
+ *
  * ### Example
  *
  * \include test/snippet/search/views/kmer_hash.cpp

diff --git a/test/snippet/search/views/kmer_hash.cpp b/test/snippet/search/views/kmer_hash.cpp
@@ -14,4 +14,13 @@ int main()
     seqan3::debug_stream << (text | seqan3::views::kmer_hash(seqan3::ungapped{3})) << '\n'; // [6,27,44,50,9]
 
     seqan3::debug_stream << (text | seqan3::views::kmer_hash(0b101_shape)) << '\n'; // [2,7,8,14,1]
+
+    // Note: the Shape is defined is from right to left. The mask 0b1101 applied to ACGT will give
+    // the same result as mask 0b111 applied to AGT.
+    {
+        auto text1 = "ACGT"_dna4;
+        auto text2 = "AGT"_dna4;
+        seqan3::debug_stream << (text1 | seqan3::views::kmer_hash(0b1101_shape)) << '\n'; // [11]
+        seqan3::debug_stream << (text2 | seqan3::views::kmer_hash(0b111_shape)) << '\n';  // [11]
+    }
 }