From 2e7e4925290b439a0c5ca2e67ae2df1243345716 Mon Sep 17 00:00:00 2001
From: odow <o.dowson@gmail.com>
Date: Fri, 28 May 2021 09:54:23 +1200
Subject: [PATCH 1/2] Document and test zero_with_output_dimension

---
 src/Utilities/functions.jl  | 12 ++++++++++++
 test/Utilities/functions.jl | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/src/Utilities/functions.jl b/src/Utilities/functions.jl
index a30cf17921..e4e5b1c061 100644
--- a/src/Utilities/functions.jl
+++ b/src/Utilities/functions.jl
@@ -566,15 +566,27 @@ function Base.getindex(
     return MOI.VectorQuadraticFunction(vat, vqt, it.f.constants[output_indices])
 end
 
+"""
+    zero_with_output_dimension(::Type{T}, output_dimension::Integer) where {T}
+
+Create an instance of type `T` with the output dimension `output_dimension`.
+
+This is mostly useful in Bridges, when code needs to be agnostic to the type of
+vector-valued function that is passed in.
+"""
+function zero_with_output_dimension end
+
 function zero_with_output_dimension(::Type{Vector{T}}, n::Integer) where {T}
     return zeros(T, n)
 end
+
 function zero_with_output_dimension(
     ::Type{MOI.VectorAffineFunction{T}},
     n::Integer,
 ) where {T}
     return MOI.VectorAffineFunction{T}(MOI.VectorAffineTerm{T}[], zeros(T, n))
 end
+
 function zero_with_output_dimension(
     ::Type{MOI.VectorQuadraticFunction{T}},
     n::Integer,
diff --git a/test/Utilities/functions.jl b/test/Utilities/functions.jl
index 181d1dedf1..51822b52f5 100644
--- a/test/Utilities/functions.jl
+++ b/test/Utilities/functions.jl
@@ -1723,3 +1723,39 @@ end
         [0.0, 0.0, 0.0],
     )
 end
+
+@testset "zero_with_output_dimension" begin
+    f = MOI.Utilities.zero_with_output_dimension(Vector{Int}, 2)
+    @test f == [0, 0]
+    @test f isa Vector{Int}
+
+    g = MOI.Utilities.zero_with_output_dimension(Vector{Float64}, 2)
+    @test g == [0.0, 0.0]
+    @test g isa Vector{Float64}
+
+    h = MOI.Utilities.zero_with_output_dimension(
+        MOI.VectorAffineFunction{Int},
+        2,
+    )
+    @test MOI.output_dimension(h) == 2
+    @test isapprox(
+        h,
+        MOI.VectorAffineFunction{Int}(MOI.VectorAffineTerm{Int}[], [0, 0]),
+    )
+    @test h isa MOI.VectorAffineFunction{Int}
+
+    i = MOI.Utilities.zero_with_output_dimension(
+        MOI.VectorQuadraticFunction{Int},
+        2,
+    )
+    @test MOI.output_dimension(i) == 2
+    @test isapprox(
+        i,
+        MOI.VectorQuadraticFunction{Int}(
+            MOI.VectorQuadraticTerm{Int}[],
+            MOI.VectorAffineTerm{Int}[],
+            [0, 0],
+        ),
+    )
+    @test i isa MOI.VectorQuadraticFunction{Int}
+end

From f5f7f4534bfe11d613751f2599e7a80a28de453d Mon Sep 17 00:00:00 2001
From: odow <o.dowson@gmail.com>
Date: Fri, 28 May 2021 09:55:08 +1200
Subject: [PATCH 2/2] Add to documentation

---
 docs/src/submodules/Utilities/reference.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/docs/src/submodules/Utilities/reference.md b/docs/src/submodules/Utilities/reference.md
index ab6cb8d6d6..253f58e2bf 100644
--- a/docs/src/submodules/Utilities/reference.md
+++ b/docs/src/submodules/Utilities/reference.md
@@ -149,6 +149,7 @@ Utilities.all_coefficients
 Utilities.unsafe_add
 Utilities.isapprox_zero
 Utilities.modify_function
+Utilities.zero_with_output_dimension
 ```
 
 The following functions can be used to canonicalize a function: