From c64872a919dd7ca09195d8175b5c5205b7565123 Mon Sep 17 00:00:00 2001
From: Jesus Bonilla <jbonilla@cimne.upc.edu>
Date: Thu, 11 Jun 2020 19:33:04 +0200
Subject: [PATCH 1/2] Added cross product operation for vectors

* Implemented the cross product for R2 and R3 VectorValue gridap types
* Added tests to assess its implementation
---
 src/TensorValues/Operations.jl            | 16 +++++++++++++++-
 test/TensorValuesTests/OperationsTests.jl | 11 +++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/src/TensorValues/Operations.jl b/src/TensorValues/Operations.jl
index ed965f828..77f427c9e 100644
--- a/src/TensorValues/Operations.jl
+++ b/src/TensorValues/Operations.jl
@@ -260,6 +260,21 @@ end
 
 const ⊗ = outer
 
+###############################################################
+# Cross Product
+###############################################################
+
+@generated function cross(a::MultiValue{Tuple{3}}, b::MultiValue{Tuple{3}})
+  str = "a[2]b[3]-a[3]b[2], a[3]b[1]-a[1]b[3], a[1]b[2]-a[2]b[1]"
+  Meta.parse("VectorValue{3}($str)")
+end
+
+@generated function cross(a::MultiValue{Tuple{2}}, b::MultiValue{Tuple{2}})
+  Meta.parse("a[1]b[2]-a[2]b[1]")
+end
+
+cross(a::MultiValue,b::MultiValue) = error("Cross product only defined for R2 and R3 vectors")
+
 ###############################################################
 # Linear Algebra
 ###############################################################
@@ -450,4 +465,3 @@ for op in (:inner,:outer)#,:(:))
         ($op)(a::Function,  b::GridapType) = operate($op,a,b)
     end
 end
-
diff --git a/test/TensorValuesTests/OperationsTests.jl b/test/TensorValuesTests/OperationsTests.jl
index 2fb8e86db..40566282d 100644
--- a/test/TensorValuesTests/OperationsTests.jl
+++ b/test/TensorValuesTests/OperationsTests.jl
@@ -263,6 +263,17 @@ c = outer(e,k)
 
 @test tr(c) == VectorValue(50,110)
 
+# Cross product
+
+a = VectorValue(1,2,3)
+b = VectorValue(3,1,6)
+c = VectorValue(9,3,-5)
+@test a × b == c
+
+a = VectorValue(2,3)
+b = VectorValue(5,2)
+@test a × b == -11
+
 # Linear Algebra
 
 t = TensorValue(10,2,30,4,5,6,70,8,9)

From cfbb71d1ba58214425b207fffa2491914861c5a4 Mon Sep 17 00:00:00 2001
From: Jesus Bonilla <jbonilla@cimne.upc.edu>
Date: Fri, 12 Jun 2020 13:15:37 +0200
Subject: [PATCH 2/2] Removed @generated from new cross methods

* Added tests for cross() function
* Updated NEWS.md
---
 NEWS.md                                   | 2 ++
 src/TensorValues/Operations.jl            | 9 ++++-----
 test/TensorValuesTests/OperationsTests.jl | 9 +++++++++
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index 2575dddc3..28f817cd5 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -12,6 +12,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - Operator `⊗` (\otimes) as an alias of `outer`. Since PR [#239](https://github.com/gridap/Gridap.jl/pull/239).
   - Support for (symmetric) 4th order tensors. Since PR [#239](https://github.com/gridap/Gridap.jl/pull/239).
   - Optimizations for symmetric 2nd order tensors. Since PR [#239](https://github.com/gridap/Gridap.jl/pull/239).
+  - Methods for `cross` function (aka `×` (\times)) to operate with `VectorValues`.
+  Since PR [#280](https://github.com/gridap/Gridap.jl/pull/280).
 
 ### Changed
 
diff --git a/src/TensorValues/Operations.jl b/src/TensorValues/Operations.jl
index 77f427c9e..f62cfee19 100644
--- a/src/TensorValues/Operations.jl
+++ b/src/TensorValues/Operations.jl
@@ -264,13 +264,12 @@ const ⊗ = outer
 # Cross Product
 ###############################################################
 
-@generated function cross(a::MultiValue{Tuple{3}}, b::MultiValue{Tuple{3}})
-  str = "a[2]b[3]-a[3]b[2], a[3]b[1]-a[1]b[3], a[1]b[2]-a[2]b[1]"
-  Meta.parse("VectorValue{3}($str)")
+function cross(a::MultiValue{Tuple{3}}, b::MultiValue{Tuple{3}})
+  VectorValue{3}(a[2]b[3]-a[3]b[2], a[3]b[1]-a[1]b[3], a[1]b[2]-a[2]b[1])
 end
 
-@generated function cross(a::MultiValue{Tuple{2}}, b::MultiValue{Tuple{2}})
-  Meta.parse("a[1]b[2]-a[2]b[1]")
+function cross(a::MultiValue{Tuple{2}}, b::MultiValue{Tuple{2}})
+  a[1]b[2]-a[2]b[1]
 end
 
 cross(a::MultiValue,b::MultiValue) = error("Cross product only defined for R2 and R3 vectors")
diff --git a/test/TensorValuesTests/OperationsTests.jl b/test/TensorValuesTests/OperationsTests.jl
index 40566282d..6f9de4da0 100644
--- a/test/TensorValuesTests/OperationsTests.jl
+++ b/test/TensorValuesTests/OperationsTests.jl
@@ -274,6 +274,15 @@ a = VectorValue(2,3)
 b = VectorValue(5,2)
 @test a × b == -11
 
+a = VectorValue(1.0,5.0,-4.0)
+b = VectorValue(6.0,2.0,3.0)
+c = VectorValue(23.0,-27.0,-28.0)
+@test cross(a, b) == c
+
+a = VectorValue(4.0,1.0)
+b = VectorValue(3.0,-2.0)
+@test cross(a, b) == -11.0
+
 # Linear Algebra
 
 t = TensorValue(10,2,30,4,5,6,70,8,9)