Merge pull request #51 from invenia/cv/non-ordered

Fixes for non-ordered intervals

Author: rofinn

src/anchoredinterval.jl

@@ -121,8 +121,18 @@ end
 
 ##### ACCESSORS #####
 
-Base.first(interval::AnchoredInterval{P}) where P = min(interval.anchor, interval.anchor+P)
-Base.last(interval::AnchoredInterval{P}) where P = max(interval.anchor, interval.anchor+P)
+# We would typically compute `first` and `last` using `min` and `max` respectively, but we
+# can get unexpected behaviour if adding the span to the anchor endpoint produces a value
+# that is no longer comparable (e.g., `NaN`).
+
+function Base.first(interval::AnchoredInterval{P}) where P
+    P < zero(P) ? (interval.anchor + P) : (interval.anchor)
+end
+
+function Base.last(interval::AnchoredInterval{P}) where P
+    P < zero(P) ? (interval.anchor) : (interval.anchor + P)
+end
+
 anchor(interval::AnchoredInterval) = interval.anchor
 span(interval::AnchoredInterval{P}) where P = abs(P)
 
@@ -209,6 +219,10 @@ end
 
 ##### EQUALITY #####
 
+function Base.:(==)(a::AnchoredInterval{P, T}, b::AnchoredInterval{P, T}) where {P, T}
+    return anchor(a) == anchor(b) && inclusivity(a) == inclusivity(b)
+end
+
 # Required for min/max of AnchoredInterval{LaxZonedDateTime} when the anchor is AMB or DNE
 function Base.isless(a::AnchoredInterval{P, T}, b::AnchoredInterval{P, T}) where {P, T}
     return (

src/interval.jl

@@ -63,8 +63,10 @@ struct Interval{T} <: AbstractInterval{T}
         # Ensure that `first` preceeds `last`.
         f, l, inc = if f ≤ l
             f, l, inc
-        else
+        elseif l ≤ f
             l, f, Inclusivity(last(inc), first(inc))
+        else
+            throw(ArgumentError("Unable to determine an ordering between: $f and $l"))
         end
 
         return new(f, l, inc)

test/anchoredinterval.jl

@@ -36,6 +36,20 @@ using Intervals: canonicalize
         @test AnchoredInterval{25}('a') isa AnchoredInterval
     end
 
+    @testset "non-ordered" begin
+        ending = AnchoredInterval{-Inf}(Inf)
+        @test isequal(first(ending), NaN)
+        @test isequal(last(ending), Inf)
+        @test ending == ending
+        @test isequal(ending, ending)
+
+        beginning = AnchoredInterval{Inf}(-Inf)
+        @test isequal(first(beginning), -Inf)
+        @test isequal(last(beginning), NaN)
+        @test beginning == beginning
+        @test isequal(beginning, beginning)
+    end
+
     @testset "hash" begin
         # Need a complicated enough element type for this test to ever fail
         zdt = now(tz"Europe/London")

test/interval.jl

@@ -37,6 +37,11 @@
         @test_throws MethodError Interval(1, 2, 3)
     end
 
+    @testset "non-ordered" begin
+        @test_throws ArgumentError Interval(NaN, Inf)
+        @test_throws ArgumentError Interval(NaN, NaN)
+    end
+
     @testset "hash" begin
         # Need a complicated enough element type for this test to ever fail
         zdt = now(tz"Europe/London")