Add tests for bigfloat and and add case fot n=0

JuliaIntervals · Aug 29, 2020 · 3b43a9d · 3b43a9d
1 parent c6f7ca3
commit 3b43a9d
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Showing 2 changed files with 22 additions and 5 deletions.
diff --git a/src/intervals/functions.jl b/src/intervals/functions.jl
@@ -329,7 +329,14 @@ hypot(a::Interval{BigFloat}, b::Interval{BigFloat}) = sqrt(a^2 + b^2)
 
 hypot(a::Interval{T}, b::Interval{T}) where T= atomic(Interval{T}, hypot(big53(a), big53(b)))
 
+"""
+nthroot(a::Interval{BigFloat}, n::Integer)
+Compute the real n-th root of Interval.
+"""
 function nthroot(a::Interval{BigFloat}, n::Integer)
+    n == 1 && return a
+    n < 0 && a == zero(a) && return emptyinterval(a)
+    isempty(a) && return a
     if n > 0
         a.hi < 0 && iseven(n) && return emptyinterval(BigFloat)
         if a.lo < 0 && a.hi >= 0 && iseven(n)
@@ -342,16 +349,14 @@ function nthroot(a::Interval{BigFloat}, n::Integer)
         ccall((:mpfr_rootn_ui, :libmpfr), Int32 , (Ref{BigFloat}, Ref{BigFloat}, Culong, MPFRRoundingMode) , high , a.hi , ui, MPFRRoundUp)
         b = interval(low , high)
         return b
-    end
-    if n < 0
+    elseif n < 0
         return inv(nthroot(a, -n))
+    elseif n == 0
+        return emptyinterval(a)
     end
 end
 
 function nthroot(a::Interval{T}, n::Integer) where T
-    n == 1 && return a
-    n < 0 && a == zero(a) && return emptyinterval(a)
-    isempty(a) && return a
     b = nthroot(big53(a), n)
     return convert(Interval{T}, b)
 end 
diff --git a/test/interval_tests/numeric.jl b/test/interval_tests/numeric.jl
@@ -396,6 +396,9 @@ end
     @test nthroot(∅, 4) == ∅
     @test nthroot(∅, -3) == ∅
     @test nthroot(∅, -4) == ∅
+    @test nthroot(Interval(1, 2), 0) == ∅
+    @test nthroot(Interval(5, 8), 0) == ∅
+    @test nthroot(Interval(1, 7), 0) == ∅
     @test nthroot(Interval(8, 27), 3) == Interval(2, 3)
     @test nthroot(Interval(0, 27), 3) == Interval(0, 3)
     @test nthroot(Interval(-27, 0), 3) == Interval(-3, 0)
@@ -414,6 +417,15 @@ end
     @test nthroot(Interval(16, 81), -4) == Interval(1/3, 1/2)
     @test nthroot(Interval(0, 81), -4) == Interval(1/3, Inf)
     @test nthroot(Interval(-81, 0), -4) == ∅
+    @test nthroot(Interval(-81, 1), 1) == Interval(-81, 1)
     @test nthroot(Interval(-81, 81), -4) == Interval(1/3, Inf)
     @test nthroot(Interval(-81, -16), -4) == ∅
+    @test nthroot(Interval(-81, -16), 1) == Interval(-81, -16)
+    @test nthroot(Interval{BigFloat}(16, 81), 4) == Interval{BigFloat}(2, 3)
+    @test nthroot(Interval{BigFloat}(0, 81), 4) == Interval{BigFloat}(0, 3)
+    @test nthroot(Interval{BigFloat}(-81, 0), 4) == Interval{BigFloat}(0)
+    @test nthroot(Interval{BigFloat}(-81, 81), 4) == Interval{BigFloat}(0, 3)
+    @test nthroot(Interval{BigFloat}(-27, 27), -3) == Interval{BigFloat}(-Inf, Inf)
+    @test nthroot(Interval{BigFloat}(-81, -16), -4) == ∅
+    @test nthroot(Interval{BigFloat}(-81, -16), 1) == Interval{BigFloat}(-81, -16)
 end