From 7145e702de5c542d6c0e88602fdf846d5fbe749f Mon Sep 17 00:00:00 2001
From: Pere Antoni Martorell <pmartorell@cimne.upc.edu>
Date: Fri, 26 Apr 2024 17:00:29 +0200
Subject: [PATCH] add zero affine map function

---
 src/Fields/AffineMaps.jl            | 6 ++++++
 src/Fields/Fields.jl                | 1 +
 test/FieldsTests/AffineMapsTests.jl | 3 +++
 3 files changed, 10 insertions(+)

diff --git a/src/Fields/AffineMaps.jl b/src/Fields/AffineMaps.jl
index 239d09530..9ce5725fc 100644
--- a/src/Fields/AffineMaps.jl
+++ b/src/Fields/AffineMaps.jl
@@ -108,3 +108,9 @@ function lazy_map(::typeof(∇),a::LazyArray{<:Fill{typeof(affine_map)}})
   gradients = a.args[1]
   lazy_map(constant_field,gradients)
 end
+
+function Base.zero(::Type{<:AffineMap{D1,D2,T}}) where {D1,D2,T}
+  gradient = TensorValue{D1,D2}(tfill(zero(T),Val{D1*D2}()))
+  origin = Point{D2,T}(tfill(zero(T),Val{D2}()))
+  AffineMap(gradient,origin)
+end
diff --git a/src/Fields/Fields.jl b/src/Fields/Fields.jl
index 0326604c4..05e5e7a56 100644
--- a/src/Fields/Fields.jl
+++ b/src/Fields/Fields.jl
@@ -8,6 +8,7 @@ import Gridap.Arrays: testitem
 
 using Gridap.Helpers: @abstractmethod, @notimplemented
 using Gridap.Helpers: @notimplementedif, @unreachable, @check
+using Gridap.Helpers: tfill
 
 using Gridap.Algebra: mul!
 
diff --git a/test/FieldsTests/AffineMapsTests.jl b/test/FieldsTests/AffineMapsTests.jl
index bd205296a..284aaec1d 100644
--- a/test/FieldsTests/AffineMapsTests.jl
+++ b/test/FieldsTests/AffineMapsTests.jl
@@ -39,6 +39,9 @@ cell_to_∇hx = lazy_map(evaluate,cell_to_∇h,cell_to_x)
 test_array(cell_to_hx,fill(hx,ncells))
 test_array(cell_to_∇hx,fill(∇hx,ncells))
 
+T = AffineMap{3,3,Int}
+@test isa(zero(T),T)
+
 #display(cell_to_hx)
 #display(cell_to_∇hx)
 #print_op_tree(cell_to_hx)