Start adding back missing functionality

Project.toml

@@ -4,8 +4,14 @@ authors = ["ITensor developers <[email protected]> and contributors"]
 version = "0.8.0"
 
 [deps]
+ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 ITensorBase = "4795dd04-0d67-49bb-8f44-b89c448a1dc7"
+LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
+TensorAlgebra = "68bd88dc-f39d-4e12-b2ca-f046b68fcc6a"
 
 [compat]
+ChainRulesCore = "1.25.1"
 ITensorBase = "0.1.2"
+LinearAlgebra = "1.10.0"
+TensorAlgebra = "0.1.1"
 julia = "1.10"

src/ITensors.jl

@@ -1,5 +1,58 @@
 module ITensors
 
+using TensorAlgebra: contract
 using ITensorBase: ITensor, Index
+include("SiteTypes/SiteTypes.jl")
+using .SiteTypes: SiteTypes
+include("LazyApply/LazyApply.jl")
+using .LazyApply: LazyApply
+include("Ops/Ops.jl")
+using .Ops: Ops
+
+# TODO: Used in `ITensorMPS.jl`, define in `BackendSelection.jl`.
+struct Algorithm{algname} end
+macro Algorithm_str(algname)
+  return :(Algorithm{$(Expr(:quote, Symbol(algname)))})
+end
+
+# TODO: Used in `ITensorMPS.jl`, decide where or if to define it.
+function outer end
+
+# TODO: Used in `ITensorMPS.jl`, decide where or if to define it.
+struct Apply{Args}
+  args::Args
+end
+
+# TODO: Used in `ITensorMPS.jl`, decide where or if to define it.
+macro ts_str(tags) end
+
+# TODO: Used in `ITensorMPS.jl`, decide where or if to define it.
+struct OneITensor end
+
+# TODO: Used in `ITensorMPS.jl`, define in `ITensorBase.jl`.
+function addtags end
+function addtags! end
+function commonind end
+function commoninds end
+function dag end
+function noprime end
+function noprime! end
+function prime end
+function prime! end
+function removetags end
+function removetags! end
+function replaceprime end
+function replaceprime! end
+function replacetags end
+function replacetags! end
+function setprime end
+function setprime! end
+function settags end
+function settags! end
+function sim end
+function swapprime end
+function swapprime! end
+function uniqueind end
+function uniqueinds end
 
 end