Linear combination dof

NEWS.md

@@ -7,11 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-## [0.20.4] - 2026-03-23
+## [0.20.4] - 2026-04-09
 
 ### Added
 
 - Added `get_free_dof_coordinates`. Since PR[#1262](https://github.com/gridap/Gridap.jl/pull/1262).
+- The element type of a `LinearCombinationDofVector` is now `LinearCombinationDof`, since PR[#1266](https://github.com/gridap/Gridap.jl/pull/1266).
 
 ### Fixed
 

src/ReferenceFEs/Dofs.jl

@@ -7,6 +7,13 @@ and the range the scalar set.
 """
 abstract type Dof <: Map end
 
+"""
+    struct LinearCombinationDof <: Dof
+
+Type to represent an element of a [`LinearCombinationDofVector`](@ref).
+"""
+struct LinearCombinationDof <: Dof end
+
 """
     struct LinearCombinationDofVector{T<:Dof,V,F} <: AbstractVector{T}
       values :: V
@@ -23,7 +30,7 @@ Fields:
 - `values::AbstractMatrix{<:Number}` the matrix of the change from dof basis (b) to (a)
 - `predofs::AbstractVector{T}` A type representing dof pre-basis (b), with `T<:Dof`
 """
-@ahe struct LinearCombinationDofVector{T,V,F} <: AbstractVector{T}
+@ahe struct LinearCombinationDofVector{T,V,F} <: AbstractVector{LinearCombinationDof}
   values::V
   predofs::F
   function LinearCombinationDofVector(
@@ -46,7 +53,7 @@ end
 
 Base.size(a::LinearCombinationDofVector) = (size(a.values,2),)
 Base.IndexStyle(::LinearCombinationDofVector) = IndexLinear()
-Base.getindex(::LinearCombinationDofVector{T},::Integer) where T = T()
+Base.getindex(::LinearCombinationDofVector,::Integer) = LinearCombinationDof()
 
 function linear_combination(a::AbstractMatrix{<:Number}, b::AbstractVector{<:Dof})
   LinearCombinationDofVector(a,b)
@@ -104,7 +111,7 @@ function Base.getindex(b::ConcatenatedDofVector, i::Integer)
   lengths = length.(bases)
   first_indices = accumulate(+, lengths)
   basis_index = findfirst(>=(i), first_indices)
-  first(bases[basis_index]) # this is PointValue() or Moment() whatever i
+  first(bases[basis_index]) # this is PointValue(..), Moment() or LinearCombinationDof() whatever i
 end
 
 function Arrays.return_cache(b::ConcatenatedDofVector, field)

test/ReferenceFEsTests/DofsTests.jl

@@ -3,6 +3,7 @@ module DofsTests
 using Test
 using Gridap
 using Gridap.ReferenceFEs
+using Gridap.ReferenceFEs: LinearCombinationDof
 using Gridap.Fields
 using FillArrays
 
@@ -19,6 +20,7 @@ dofs  = get_dof_basis(reffe0)                  # length 3
 dofs_lc = linear_combination(Eye(3,6), dofs)   # length 6
 @test dofs_lc isa AbstractVector{<:Dof}
 @test length(dofs_lc) == 6
+@test dofs_lc[1] isa LinearCombinationDof
 
 basis = get_prebasis(reffe1)                   # length 4
 @test basis    isa AbstractVector{<:Field}