Move nsubsystems from QOBase (#19)

ba2tripleO · web-flow · commit 35e721bfc5d5 · 2023-09-21T17:11:49.000-04:00
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # News
 
+## v0.3.3
+
+- Add `nsubsystems` for computing the number of subsystems in a state.
+
 ## v0.3.2
 
 - Cleanup - removing forgotten debug print statements.
diff --git a/Project.toml b/Project.toml
@@ -1,7 +1,7 @@
 name = "QuantumInterface"
 uuid = "5717a53b-5d69-4fa3-b976-0bf2f97ca1e5"
 authors = ["QuantumInterface.jl contributors"]
-version = "0.3.2"
+version = "0.3.3"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
diff --git a/src/embed_permute.jl b/src/embed_permute.jl
@@ -84,3 +84,8 @@ function embed(basis_l::CompositeBasis, basis_r::CompositeBasis,
 end
 
 permutesystems(a::AbstractOperator, perm) = arithmetic_unary_error("Permutations of subsystems", a)
+
+nsubsystems(s::AbstractKet) = nsubsystems(basis(s))
+nsubsystems(s::AbstractOperator) = nsubsystems(basis(s))
+nsubsystems(b::CompositeBasis) = length(b.bases)
+nsubsystems(b::Basis) = 1
