Add get method, tests for Tuple and AbstractArrays (JuliaLang#41007)

Replaces JuliaLang#40856
Fixes JuliaLang#40809

Author: Pramodh Gopalan V

base/abstractarray.jl

@@ -1469,6 +1469,9 @@ RangeVecIntList{A<:AbstractVector{Int}} = Union{Tuple{Vararg{Union{AbstractRange
 get(A::AbstractArray, i::Integer, default) = checkbounds(Bool, A, i) ? A[i] : default
 get(A::AbstractArray, I::Tuple{}, default) = checkbounds(Bool, A) ? A[] : default
 get(A::AbstractArray, I::Dims, default) = checkbounds(Bool, A, I...) ? A[I...] : default
+get(f::Callable, A::AbstractArray, i::Integer) = checkbounds(Bool, A, i) ? A[i] : f()
+get(f::Callable, A::AbstractArray, I::Tuple{}) = checkbounds(Bool, A) ? A[] : f()
+get(f::Callable, A::AbstractArray, I::Dims) = checkbounds(Bool, A, I...) ? A[I...] : f()
 
 function get!(X::AbstractVector{T}, A::AbstractVector, I::Union{AbstractRange,AbstractVector{Int}}, default::T) where T
     # 1d is not linear indexing

base/tuple.jl

@@ -32,6 +32,9 @@ getindex(t::Tuple, r::AbstractArray{<:Any,1}) = (eltype(t)[t[ri] for ri in r]...
 getindex(t::Tuple, b::AbstractArray{Bool,1}) = length(b) == length(t) ? getindex(t, findall(b)) : throw(BoundsError(t, b))
 getindex(t::Tuple, c::Colon) = t
 
+get(t::Tuple, i::Integer, default) = i in 1:length(t) ? getindex(t, i) : default
+get(f::Callable, t::Tuple, i::Integer) = i in 1:length(t) ? getindex(t, i) : f()
+
 # returns new tuple; N.B.: becomes no-op if i is out-of-bounds
 
 """

test/abstractarray.jl

@@ -598,6 +598,31 @@ function test_get(::Type{TestAbstractArray})
     @test get(TSlow([]), (), 0) == 0
     @test get(TSlow([1]), (), 0) == 1
     @test get(TSlow(fill(1)), (), 0) == 1
+
+    global c = 0
+    f() = (global c = c+1; 0)
+    @test get(f, A, ()) == 0
+    @test c == 1
+    @test get(f, B, ()) == 0
+    @test c == 2
+    @test get(f, A, (1,)) == get(f, A, 1) == A[1] == 1
+    @test c == 2
+    @test get(f, B, (1,)) == get(f, B, 1) == B[1] == 1
+    @test c == 2
+    @test get(f, A, (25,)) == get(f, A, 25) == 0
+    @test c == 4
+    @test get(f, B, (25,)) == get(f, B, 25) == 0
+    @test c == 6
+    @test get(f, A, (1,1,1)) == A[1,1,1] == 1
+    @test get(f, B, (1,1,1)) == B[1,1,1] == 1
+    @test get(f, A, (1,1,3)) == 0
+    @test c == 7
+    @test get(f, B, (1,1,3)) == 0
+    @test c == 8
+    @test get(f, TSlow([]), ()) == 0
+    @test c == 9
+    @test get(f, TSlow([1]), ()) == 1
+    @test get(f, TSlow(fill(1)), ()) == 1
 end
 
 function test_cat(::Type{TestAbstractArray})

test/tuple.jl

@@ -179,6 +179,15 @@ end
         @test_throws MethodError (1,)[]
         @test_throws MethodError (1,1,1)[1,1]
     end
+
+    @testset "get() method for Tuple (Issue #40809)" begin
+        @test get((5, 6, 7), 1, 0) == 5
+        @test get((), 5, 0) == 0
+        @test get((1,), 3, 0) == 0
+        @test get(()->0, (5, 6, 7), 1) == 5
+        @test get(()->0, (), 4) == 0
+        @test get(()->0, (1,), 3) == 0
+    end
 end
 
 @testset "fill to length" begin