SU2 as a concrete type

NDTensors/src/lib/Sectors/src/category_definitions/su.jl

@@ -95,12 +95,12 @@ function label_fusion_rule(::Type{<:SU{2}}, s1, s2)
 end
 
 # define angular momentum-like interface using half-integers
-# SU2 is an alias for SU{2}
-const SU2 = SU{2}
+const SU2 = SU{2,1}  # intuitive alias
 
 # specific constructor for SU{2} with a half-integer
 # note that SU{2}(1) = spin 1 while SU{2}((1,)) = spin 1/2
-SU{2}(h::Number) = SU{2}((HalfIntegers.twice(HalfIntegers.HalfInteger(h)),))
+SU{2}(h::Number) = SU{2,1}(h)
+SU{2,1}(h::Number) = SU{2,1}((HalfIntegers.twice(HalfIntegers.HalfInteger(h)),))
 
 # display SU2 using half-integers
 function Base.show(io::IO, s::SU{2})

NDTensors/src/lib/Sectors/test/test_simple_categories.jl

@@ -42,15 +42,18 @@ using Test: @inferred, @test, @testset
 
   @testset "SU2" begin
     j1 = SU2(0)
-    j2 = SU2(1//2)
+    j2 = SU2(1//2)  # Rational will be cast to HalfInteger
     j3 = SU2(1)
     j4 = SU2(3//2)
 
-    # alternative tuple constructor
-    @test j1 == SU{2}((0,))
-    @test j2 == SU{2}((1,))
-    @test j3 == SU{2}((2,))
-    @test j4 == SU((3,))  # infer N from tuple length
+    # alternative constructors
+    @test j2 == SU{2}((1,))  # tuple SU(N)-like constructor
+    @test j2 == SU{2,1}((1,))  # tuple constructor with explicit {N,N-1}
+    @test j2 == SU{2}(1//2)  # half-integer constructor without N-1
+    @test j2 == SU((1,))  # infer N from tuple length
+    @test j2 == SU{2}((Int8(1),))  # any Integer type accepted
+    @test j2 == SU{2}((UInt32(1),))  # any Integer type accepted
+    @test j2 == SU2(1 / 2)  # Float will be cast to HalfInteger
 
     @test trivial(SU2) == SU2(0)
     @test istrivial(SU2(0))