From c1f0b82c39f090edd2840cd43bcc8c5e3cf87098 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Carlos=20Vigil-V=C3=A1squez?= <carlos.vigil.v@gmail.com>
Date: Wed, 21 Jan 2026 11:30:31 +0100
Subject: [PATCH] fix: correct n-grams encoding

Behavior wasn't deterministic for some reason, producing errors in some
cases.
---
 src/encoding.jl  | 6 ++++--
 test/encoding.jl | 3 ++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/encoding.jl b/src/encoding.jl
index e793174..f5f69ba 100644
--- a/src/encoding.jl
+++ b/src/encoding.jl
@@ -437,13 +437,15 @@ and shift operations.
 # References
 
 - [Torchhd documentation](https://torchhd.readthedocs.io/en/stable/generated/torchhd.ngrams.html)
-
 """
 function ngrams(vs::AbstractVector{<:AbstractHV}, n::Int = 3)
     l = length(vs)
     p = l - n + 1
     @assert 1 <= n <= length(vs) "`n` must be 1 ≤ n ≤ $l"
-    return bundle([bind([shift(vs[i + j], j) for j in 0:(n - 1)]) for i in 1:p])
+    return map(
+        s -> bindsequence(s),
+        (vs[f:(f + (n - 1))] for f in 1:p)
+    ) |> multiset
 end
 
 """
diff --git a/test/encoding.jl b/test/encoding.jl
index ff6180f..0d851a2 100644
--- a/test/encoding.jl
+++ b/test/encoding.jl
@@ -37,7 +37,8 @@
     end
 
     @testset "ngrams" begin
-        @test ngrams(hvs) == Bool.([0, 1, 0, 0, 1])
+        @test ngrams(hvs).v == Bool.([0, 1, 0, 0, 1])
+        @test ngrams(hvs) == bundle([hvs[1] * ρ(hvs[2]) * ρ(hvs[3], 2), hvs[2] * ρ(hvs[3]) * ρ(hvs[4], 2), hvs[3] * ρ(hvs[4]) * ρ(hvs[5], 2)])
         @test_throws AssertionError ngrams(hvs, 0)
         @test_throws AssertionError ngrams(hvs, length(hvs) + 1)
     end