fix LazyMath begin end indexing (#685)

* fix LazyMath indexing

* fixes and tests

Author: rafaqz

src/Dimensions/indexing.jl

@@ -110,7 +110,7 @@ _unwrapdim(x) = x
 @inline _dims2indices(dim::Dimension, ::Type{<:Dimension}) = Colon()
 # Nothing means nothing was passed for this dimension
 @inline _dims2indices(dim::Dimension, i::AbstractBeginEndRange) = i
-@inline _dims2indices(dim::Dimension, i::Union{LU.Begin,LU.End,Type{LU.Begin},Type{LU.End}}) = 
+@inline _dims2indices(dim::Dimension, i::Union{LU.Begin,LU.End,Type{LU.Begin},Type{LU.End},LU.LazyMath}) = 
     to_indices(parent(dim), LU._construct_types(i))[1]
 @inline _dims2indices(dim::Dimension, ::Nothing) = Colon()
 @inline _dims2indices(dim::Dimension, x) = Lookups.selectindices(val(dim), x)

src/Lookups/beginend.jl

@@ -39,10 +39,8 @@ Base.to_indices(A, inds, (r, args...)::Tuple{BeginEndRange,Vararg}) =
     (_to_index(inds[1], r.start):_to_index(inds[1], r.stop), to_indices(A, Base.tail(inds), args)...)
 Base.to_indices(A, inds, (r, args...)::Tuple{BeginEndStepRange,Vararg}) =
     (_to_index(inds[1], r.start):r.step:_to_index(inds[1], r.stop), to_indices(A, Base.tail(inds), args)...)
-Base.to_indices(A, inds, (r, args...)::Tuple{Begin,Vararg}) =
-    (first(inds[1]), to_indices(A, Base.tail(inds), args)...)
-Base.to_indices(A, inds, (r, args...)::Tuple{End,Vararg}) =
-    (last(inds[1]), to_indices(A, Base.tail(inds), args)...)
+Base.to_indices(A, inds, (r, args...)::Tuple{<:Union{Begin,End,<:LazyMath},Vararg}) =
+    (_to_index(inds[1], r), to_indices(A, Base.tail(inds), args)...)
 
 _to_index(inds, a::Int) = a
 _to_index(inds, ::Begin) = first(inds)
@@ -92,8 +90,8 @@ _pf(f) = string(f)
 for T in (UnitRange, AbstractUnitRange, StepRange, StepRangeLen, LinRange, Lookup)
     for f in (:getindex, :view, :dotview)
         @eval Base.$f(A::$T, i::AbstractBeginEndRange) = Base.$f(A, to_indices(A, (i,))...)
-        @eval Base.$f(A::$T, ::Type{Begin}) = Base.$f(A, firstindex(A)) 
-        @eval Base.$f(A::$T, ::Type{End}) = Base.$f(A, lastindex(A)) 
+        @eval Base.$f(A::$T, i::Union{Type{Begin},Type{End},Begin,End,LazyMath}) = 
+            Base.$f(A, to_indices(A, _construct_types(i))...) 
     end
 end
 

test/indexing.jl

@@ -31,8 +31,8 @@ end
 @testset "lookup" begin
     @testset "Points" begin
         l = Sampled(2.0:2.0:10, ForwardOrdered(), Regular(2.0), Points(), nothing)
-        @test l[:] == l[Begin:End] == l
-        @test l[Begin:5] == l[1:5] == l
+        @test l[:] == l[Begin:End] == l[1:End] == l[Begin:5] == l[1:5] == l
+        @test l[Begin+1:End-1] ==l[Begin+1:4] ==  l[2:End-1] == l[2:4]
         @test l[Begin:End] isa typeof(l)
         @test l[1:5] isa typeof(l)
         @test l[[1, 3, 4]] == view(l, [1, 3, 4]) == 
@@ -161,6 +161,7 @@ end
     @test @inferred d[1:5] == d
     @test d[1:5] isa typeof(d)
     @test @inferred d[Begin:End] == d
+    @test d[Begin+1:End-1] == d[2:-1+End] == d[1+Begin:4] == d[2:4]
     @test d[Begin:End] isa typeof(d)
     # TODO properly handle index mashing arrays: here Regular should become Irregular
     # @test d[[1, 3, 4]] == X(Sampled([2.0, 6.0, 8.0], ForwardOrdered(), Regular(2.0), Points(), nothing))