Move isleftcanonical,isrightcanonical to source

src/Ansatz/Chain.jl

@@ -187,6 +187,36 @@ function canonize_site!(::Open, tn::Chain, site::Site; direction::Symbol, method
     return tn
 end
 
+function isleftcanonical(qtn::Chain, site; atol::Real = 1e-12)
+    right_ind = rightindex(qtn, site)
+
+    # we are at right-most site, which cannot be left-canonical
+    if isnothing(right_ind)
+        return false
+    end
+
+    # TODO is replace(conj(A)...) copying too much?
+    tensor = select(qtn, :tensor, site)
+    contracted = contract(tensor, replace(conj(tensor), right_ind => :new_ind_name))
+
+    return isapprox(contracted, Matrix{Float64}(I, size(A, right_ind), size(A, right_ind)); atol)
+end
+
+function isrightcanonical(qtn::Chain, site; atol::Real = 1e-12)
+    left_ind = leftindex(qtn, site)
+
+    # we are at left-most site, which cannot be right-canonical
+    if isnothing(left_ind)
+        return false
+    end
+
+    #TODO is replace(conj(A)...) copying too much?
+    tensor = select(qtn, :tensor, site)
+    contracted = contract(tensor, replace(conj(tensor), left_ind => :new_ind_name))
+
+    return isapprox(contracted, Matrix{Float64}(I, size(A, left_ind), size(A, left_ind)); atol)
+end
+
 mixed_canonize(tn::Chain, args...; kwargs...) = mixed_canonize!(deepcopy(tn), args...; kwargs...)
 mixed_canonize!(tn::Chain, args...; kwargs...) = mixed_canonize!(boundary(tn), tn, args...; kwargs...)
 

test/Ansatz/Chain_test.jl

@@ -54,28 +54,6 @@
     @testset "Canonization" begin
         using Tenet
 
-        function is_left_canonical(qtn, s::Site)
-            label_r = rightindex(qtn, s)
-            A = select(qtn, :tensor, s)
-            try
-                contracted = contract(A, replace(conj(A), label_r => :new_ind_name))
-                return isapprox(contracted, Matrix{Float64}(I, size(A, label_r), size(A, label_r)), atol = 1e-12)
-            catch
-                return false
-            end
-        end
-
-        function is_right_canonical(qtn, s::Site)
-            label_l = leftindex(qtn, s)
-            A = select(qtn, :tensor, s)
-            try
-                contracted = contract(A, replace(conj(A), label_l => :new_ind_name))
-                return isapprox(contracted, Matrix{Float64}(I, size(A, label_l), size(A, label_l)), atol = 1e-12)
-            catch
-                return false
-            end
-        end
-
         @testset "canonize_site" begin
             qtn = Chain(State(), Open(), [rand(4, 4), rand(4, 4, 4), rand(4, 4)])