Introduce a copy(M,p) and a copy(M, p, X) command (#77)

* Introduce a `copy` command for points (on manifolds) and (tangent) vectors.

Project.toml

@@ -1,7 +1,7 @@
 name = "ManifoldsBase"
 uuid = "3362f125-f0bb-47a3-aa74-596ffd7ef2fb"
 authors = ["Seth Axen <[email protected]>", "Mateusz Baran <[email protected]>", "Ronny Bergmann <[email protected]>", "Antoine Levitt <[email protected]>"]
-version = "0.12.1"
+version = "0.12.2"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"

src/ManifoldsBase.jl

@@ -5,6 +5,7 @@ import Base:
     exp,
     log,
     convert,
+    copy,
     copyto!,
     angle,
     eltype,
@@ -81,7 +82,7 @@ end
 Return type of element of the array that will represent the result of function `f` and the
 [`AbstractManifold`](@ref) `M` on given arguments `args` (passed as a tuple).
 """
-function allocate_result_type(M::AbstractManifold, f, args::NTuple{N,Any}) where {N}
+function allocate_result_type(::AbstractManifold, f, args::NTuple{N,Any}) where {N}
     return typeof(mapreduce(eti -> one(number_eltype(eti)), +, args))
 end
 
@@ -175,6 +176,33 @@ function check_size(M::AbstractManifold, p, X)
     end
 end
 
+@doc raw"""
+    copy(M, p)
+
+Copy the value(s) from the point `p` on the [`AbstractManifold`](@ref) `M` into a new point.
+See [`allocate_result`](@ref) for the allocation of new point memory and [`copyto!`](@ref) for the copying.
+"""
+function copy(M::AbstractManifold, p)
+    q = allocate_result(M, copy, p)
+    copyto!(M, q, p)
+    return q
+end
+
+@doc raw"""
+    copy(M, p, X)
+
+Copy the value(s) from the tangent vector `X` at a point `p` on the
+[`AbstractManifold`](@ref) `M` into a new tangent vector.
+See [`allocate_result`](@ref) for the allocation of new point memory and [`copyto!`](@ref) for the copying.
+"""
+function copy(M::AbstractManifold, p, X)
+    # the order of args switched, since the allocation by default takes the type of the first.
+    Y = allocate_result(M, copy, X, p)
+    copyto!(M, Y, p, X)
+    return Y
+end
+
+
 @doc raw"""
     copyto!(M::AbstractManifold, q, p)
 
@@ -272,8 +300,7 @@ see [`AbstractEmbeddedManifold`](@ref) how you can avoid reimplementing code fro
 See also: [`EmbeddedManifold`](@ref), [`project`](@ref project(M::AbstractManifold, p, X))
 """
 function embed(M::AbstractManifold, p, X)
-    # Note that the order is switched,
-    # since the allocation by default takes the type of the first.
+    # the order of args switched, since the allocation by default takes the type of the first.
     Y = allocate_result(M, embed, X, p)
     embed!(M, Y, p, X)
     return Y
@@ -596,6 +623,8 @@ export allocate,
     check_point,
     check_vector,
     check_size,
+    copy,
+    copyto!,
     distance,
     exp,
     exp!,

test/default_manifold.jl

@@ -306,4 +306,20 @@ Base.size(x::MatrixVectorTransport) = (size(x.m, 2),)
         a = NLsolveInverseRetraction(ExponentialRetraction())
         @test a.retraction isa ExponentialRetraction
     end
+
+    @testset "copy of points and vectors" begin
+        M = DefaultManifold(2)
+        p = [2.0, 3.0]
+        q = similar(p)
+        copyto!(M, q, p)
+        @test p == q
+        r = copy(M, p)
+        @test r == p
+        X = [4.0, 5.0]
+        Y = similar(X)
+        copyto!(M, Y, p, X)
+        @test Y == X
+        Z = copy(M, p, X)
+        @test Z == X
+    end
 end