Fix power_rev for exponents that are integer-valued but not integer-t…

…yped (#38)

* Treat exponent 2.0 as if it were 2 by calling the integer version of power_rev

* Fix return type and add test

* Bump version

Project.toml

@@ -1,6 +1,6 @@
 name = "IntervalContractors"
 uuid = "15111844-de3b-5229-b4ba-526f2f385dc9"
-version = "0.4.0"
+version = "0.4.1"
 
 [deps]
 IntervalArithmetic = "d1acc4aa-44c8-5952-acd4-ba5d80a2a253"

src/arithmetic.jl

@@ -120,6 +120,11 @@ end
 
 function power_rev(a::Interval, b::Interval, c::Interval)  # a = b^c
 
+    if isinteger(c)
+        temp = power_rev(a, b, Int(inf(c)))  # use version with integer
+        return (temp[1], temp[2], interval(temp[3]))
+    end
+
     b_new = b ∩ ( a^(inv(c) ))
     c_new = c ∩ (log(a) / log(b))
 

test/runtests.jl

@@ -20,4 +20,8 @@ using Test
 
         @test mul_rev(z, x, y) == (2..10, 2..5, 0.4..1.0)
     end
+
+    @testset "Exponents with integer values but not types" begin
+        @test power_rev(-Inf..Inf, -4..4, 2.0) ==  (-∞..∞, -4..4, 2.0)
+    end
 end