--- a/src/LazyTensors/lazy_tensor_operations.jl	Fri Jan 31 15:52:49 2025 +0100
+++ b/src/LazyTensors/lazy_tensor_operations.jl	Fri Jan 31 20:35:28 2025 +0100
@@ -52,24 +52,66 @@
 domain_size(tmt::TensorTranspose) = range_size(tmt.tm)
 
 
-struct ElementwiseTensorOperation{Op,T,R,D,T1<:LazyTensor{T,R,D},T2<:LazyTensor{T,R,D}} <: LazyTensor{T,R,D}
-    tm1::T1
-    tm2::T2
+"""
+    TensorNegation{T,R,D,...} <: LazyTensor{T,R,D}
+
+The negation of a LazyTensor.
+"""
+struct TensorNegation{T,R,D,TM<:LazyTensor{T,R,D}} <: LazyTensor{T,R,D}
+    tm::TM
+end
+
+apply(tm::TensorNegation, v, I...) = -apply(tm.tm, v, I...)
+apply_transpose(tm::TensorNegation, v, I...) = -apply_transpose(tm.tm, v, I...)
+
+range_size(tm::TensorNegation) = range_size(tm.tm)
+domain_size(tm::TensorNegation) = domain_size(tm.tm)
+
 
-    function ElementwiseTensorOperation{Op,T,R,D}(tm1::T1,tm2::T2) where {Op,T,R,D, T1<:LazyTensor{T,R,D},T2<:LazyTensor{T,R,D}}
-        @boundscheck check_domain_size(tm2, domain_size(tm1))
-        @boundscheck check_range_size(tm2, range_size(tm1))
-        return new{Op,T,R,D,T1,T2}(tm1,tm2)
+"""
+    TensorSum{T,R,D,...} <: LazyTensor{T,R,D}
+
+The lazy sum of 2 or more lazy tensors.
+"""
+struct TensorSum{T,R,D,TT<:NTuple{N, LazyTensor{T,R,D}} where N} <: LazyTensor{T,R,D}
+    tms::TT
+
+    function TensorSum{T,R,D}(tms::TT) where {T,R,D, TT<:NTuple{N, LazyTensor{T,R,D}} where N}
+        @boundscheck map(tms) do tm
+            check_domain_size(tm, domain_size(tms[1]))
+            check_range_size(tm, range_size(tms[1]))
+        end
+
+        return new{T,R,D,TT}(tms)
     end
 end
 
-ElementwiseTensorOperation{Op}(s,t) where Op = ElementwiseTensorOperation{Op,eltype(s), range_dim(s), domain_dim(s)}(s,t)
+"""
+    TensorSum(ts::Vararg{LazyTensor})
+
+The lazy sum of the tensors `ts`.
+"""
+function TensorSum(ts::Vararg{LazyTensor})
+    T = eltype(ts[1])
+    R = range_dim(ts[1])
+    D = domain_dim(ts[1])
+    return TensorSum{T,R,D}(ts)
+end
 
-apply(tmBinOp::ElementwiseTensorOperation{:+,T,R,D}, v::AbstractArray{<:Any,D}, I::Vararg{Any,R}) where {T,R,D} = apply(tmBinOp.tm1, v, I...) + apply(tmBinOp.tm2, v, I...)
-apply(tmBinOp::ElementwiseTensorOperation{:-,T,R,D}, v::AbstractArray{<:Any,D}, I::Vararg{Any,R}) where {T,R,D} = apply(tmBinOp.tm1, v, I...) - apply(tmBinOp.tm2, v, I...)
+function apply(tmBinOp::TensorSum{T,R,D}, v::AbstractArray{<:Any,D}, I::Vararg{Any,R}) where {T,R,D}
+    return sum(tmBinOp.tms) do tm
+        apply(tm,v,I...)
+    end
+end
 
-range_size(tmBinOp::ElementwiseTensorOperation) = range_size(tmBinOp.tm1)
-domain_size(tmBinOp::ElementwiseTensorOperation) = domain_size(tmBinOp.tm1)
+function apply_transpose(tmBinOp::TensorSum{T,R,D}, v::AbstractArray{<:Any,D}, I::Vararg{Any,R}) where {T,R,D}
+    return sum(tmBinOp.tms) do tm
+        apply_transpose(tm,v,I...)
+    end
+end
+
+range_size(tmBinOp::TensorSum) = range_size(tmBinOp.tms[1])
+domain_size(tmBinOp::TensorSum) = domain_size(tmBinOp.tms[1])
 
 
 """
@@ -121,7 +163,6 @@
 
 Base.:*(a::T, tm::LazyTensor{T}) where T = TensorComposition(ScalingTensor{T,range_dim(tm)}(a,range_size(tm)), tm)
 Base.:*(tm::LazyTensor{T}, a::T) where T = a*tm
-Base.:-(tm::LazyTensor) = (-one(eltype(tm)))*tm
 
 """
     InflatedTensor{T,R,D} <: LazyTensor{T,R,D}