define GeometryStyle and OperatorStyle for multiple arguments by recursion

Author: AFeuerpfeil

src/utility/styles.jl

@@ -10,6 +10,12 @@ Trait to describe the operator behavior of the input `x` or type `T`, which can
 abstract type OperatorStyle end
 OperatorStyle(x) = OperatorStyle(typeof(x))
 OperatorStyle(T::Type) = throw(MethodError(OperatorStyle, T)) # avoid stackoverflow if not defined
+OperatorStyle(x::OperatorStyle) = x 
+
+OperatorStyle(x, y) = OperatorStyle(OperatorStyle(x)::OperatorStyle, OperatorStyle(y)::OperatorStyle)
+OperatorStyle(::T, ::T) where {T<:OperatorStyle} = T()
+OperatorStyle(x::OperatorStyle, y::OperatorStyle) = throw(MethodError(OperatorStyle, (x, y)))
+@inline OperatorStyle(x, y, zs...) = OperatorStyle(OperatorStyle(x, y), zs...)
 
 struct MPOStyle <: OperatorStyle end
 struct HamiltonianStyle <: OperatorStyle end
@@ -29,6 +35,12 @@ Trait to describe the geometry of the input `x` or type `T`, which can be either
 abstract type GeometryStyle end
 GeometryStyle(x) = GeometryStyle(typeof(x))
 GeometryStyle(T::Type) = throw(MethodError(GeometryStyle, T)) # avoid stackoverflow if not defined
+GeometryStyle(x::GeometryStyle) = x
+
+GeometryStyle(x, y) = GeometryStyle(GeometryStyle(x)::GeometryStyle, GeometryStyle(y)::GeometryStyle)
+GeometryStyle(::T, ::T) where {T<:GeometryStyle} = T()
+GeometryStyle(x::GeometryStyle, y::GeometryStyle) = throw(MethodError(GeometryStyle, (x, y)))
+@inline GeometryStyle(x, y, zs...) = GeometryStyle(GeometryStyle(x, y), zs...)
 
 struct FiniteChainStyle <: GeometryStyle end
 struct InfiniteChainStyle <: GeometryStyle end

test/operators.jl

@@ -71,6 +71,8 @@ module TestOperators
             mps₁ = FiniteMPS(ψ₁)
             mps₂ = FiniteMPS(ψ₂)
 
+            @test @constinferred GeometryStyle(mps₁, mpo₁, mps₁) == GeometryStyle(mps₁)
+
             @test convert(TensorMap, mpo₁ * mps₁) ≈ O₁ * ψ₁
             @test mpo₁ * ψ₁ ≈ O₁ * ψ₁
             @test convert(TensorMap, mpo₃ * mps₁) ≈ O₃ * ψ₁
@@ -140,6 +142,7 @@ module TestOperators
         @test GeometryStyle(H) == FiniteChainStyle()
         @test OperatorStyle(typeof(H)) == HamiltonianStyle()
         @test OperatorStyle(H) == HamiltonianStyle()
+        @test OperatorStyle(H, H´) == OperatorStyle(H)
 
         # Infinite
         Ws = [Wmid]
@@ -410,6 +413,8 @@ module TestOperators
         ψ = InfiniteMPS([pspace], [ou ⊕ pspace])
 
         W = MPSKit.DenseMPO(make_time_mpo(ham, 1im * 0.5, WII()))
+
+        @test GeometryStyle(ψ, W) == GeometryStyle(ψ)
         @test W * (W * ψ) ≈ (W * W) * ψ atol = 1.0e-2 # TODO: there is a normalization issue here
     end
 

test/other.jl

@@ -120,5 +120,11 @@ module TestMiscellaneous
         @test GeometryStyle(FiniteMPOHamiltonian) == FiniteChainStyle()
         @test GeometryStyle(InfiniteMPO) == InfiniteChainStyle()
         @test GeometryStyle(InfiniteMPOHamiltonian) == InfiniteChainStyle()
+
+        @test GeometryStyle(GeometryStyle(FiniteMPS)) == GeometryStyle(FiniteMPS)
+        @test GeometryStyle(FiniteMPS, FiniteMPO) == FiniteChainStyle()
+        @test_throws MethodError GeometryStyle(FiniteMPS, InfiniteMPO)
+        @test @constinferred GeometryStyle(InfiniteMPS, InfiniteMPO, InfiniteMPS) == InfiniteChainStyle()
+        @test_throws MethodError GeometryStyle(FiniteMPS, FiniteMPO, InfiniteMPS)
     end
 end