Add hashing for Intervals (#161)

* Add hashing for Intervals

* Add more tests

* Add docstring

Author: eeshan9815

src/IntervalArithmetic.jl

@@ -27,7 +27,7 @@ import Base:
     isfinite, isnan, isinf, iszero,
     show, showall,
     isinteger, setdiff,
-    parse
+    parse, hash
 
 import Base:  # for IntervalBox
     broadcast, dot, length,

src/intervals/intervals.jl

@@ -156,3 +156,8 @@ end
 
 a ± b = (a-b)..(a+b)
 ±(a::Interval, b) = (a.lo - b)..(a.hi + b)
+
+"""
+Computes the integer hash code for an `Interval` using the method for composite types used in `AutoHashEquals.jl`
+"""
+hash(x::Interval, h::UInt) = hash(x.hi, hash(x.lo, hash(:Interval, h)))

test/interval_tests/construction.jl

@@ -311,3 +311,21 @@ end
 @testset "a..b with a > b" begin
     @test_throws ArgumentError 3..2
 end
+
+@testset "Hashing of Intervals" begin
+    x = Interval{Float64}(1, 2)
+    y = Interval{BigFloat}(1, 2)
+    @test isequal(x, y)
+    @test isequal(hash(x), hash(y))
+
+    x = @interval(0.1)
+    y = IntervalArithmetic.big53(x)
+    @test isequal(x, y)
+    @test isequal(hash(x), hash(y))
+
+    x = interval(1, 2)
+    y = interval(1, 3)
+    @test !isequal(x, y)
+    @test !isequal(hash(x), hash(y))
+
+end