Add intersect(::AbstractRange, ::AbstractRange)

JuliaLang · Aug 4, 2021 · 8c2c523 · 8c2c523
1 parent 5262f3f
commit 8c2c523
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diff --git a/base/range.jl b/base/range.jl
@@ -1143,6 +1143,13 @@ function intersect(r::StepRange, s::StepRange)
     step(r) < zero(step(r)) ? StepRange{T,S}(n, -a, m) : StepRange{T,S}(m, a, n)
 end
 
+function intersect(r1::AbstractRange, r2::AbstractRange)
+    if length(r2) < length(r1)
+        r1, r2 = r2, r1
+    end
+    return [x for x in r1 if x ∈ r2]
+end
+
 function intersect(r1::AbstractRange, r2::AbstractRange, r3::AbstractRange, r::AbstractRange...)
     i = intersect(intersect(r1, r2), r3)
     for t in r

diff --git a/test/ranges.jl b/test/ranges.jl
@@ -412,6 +412,19 @@ end
             @test intersect(start-Day(10):Day(1):stop-Day(10), start:Day(5):stop) ==
                 start:Day(5):stop-Day(10)-mod(stop-start, Day(5))
         end
+
+        @testset "Two AbstractRanges" begin
+            struct DummyRange{T} <: AbstractRange{T}
+                r::UnitRange{T}
+            end
+            Base.iterate(dr::DummyRange) = iterate(dr.r)
+            Base.iterate(dr::DummyRange, state) = iterate(dr.r, state)
+            Base.length(dr::DummyRange) = length(dr.r)
+            Base.in(x::Int, dr::DummyRange) = in(x, dr.r)
+            r1 = DummyRange(1:5)
+            r2 = DummyRange(3:6)
+            @test intersect(r1, r2) === [3, 4, 5]
+        end
     end
     @testset "issubset" begin
         @test issubset(1:3, 1:typemax(Int)) #32461