Merge pull request #393 from krish8484/cxsc

Completes c-xsc.jl
JuliaIntervals · Sep 6, 2020 · a1cbb81 · a1cbb81
2 parents d3a318c + 3b43a9d
commit a1cbb81
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Showing 5 changed files with 462 additions and 1 deletion.
diff --git a/src/IntervalArithmetic.jl b/src/IntervalArithmetic.jl
@@ -54,7 +54,7 @@ export
     interval,
     @interval, @biginterval, @floatinterval, @make_interval,
     diam, radius, mid, mag, mig, hull,
-    emptyinterval, ∅, ∞, isempty, isinterior, ⪽,
+    emptyinterval, ∅, ∞, isempty, isinterior, ⪽, nthroot,
     precedes, strictprecedes, ≼, ≺, ⊂, ⊃, ⊇, contains_zero,
     entireinterval, isentire, nai, isnai, isthin, iscommon, isatomic,
     widen, inf, sup, bisect, mince,

diff --git a/src/intervals/functions.jl b/src/intervals/functions.jl
@@ -285,6 +285,7 @@ for f in (:exp, :expm1)
     end
 end
 
+
 for f in (:exp2, :exp10, :cbrt)
 
     @eval function ($f)(x::BigFloat, r::RoundingMode)  # add BigFloat functions with rounding:
@@ -327,3 +328,35 @@ end
 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)
+            a = a ∩ Interval{BigFloat}(0, Inf)
+        end
+        ui = convert(Culong, n)
+        low = BigFloat()
+        high = BigFloat()
+        ccall((:mpfr_rootn_ui, :libmpfr), Int32 , (Ref{BigFloat}, Ref{BigFloat}, Culong, MPFRRoundingMode) , low , a.lo , ui, MPFRRoundDown)
+        ccall((:mpfr_rootn_ui, :libmpfr), Int32 , (Ref{BigFloat}, Ref{BigFloat}, Culong, MPFRRoundingMode) , high , a.hi , ui, MPFRRoundUp)
+        b = interval(low , high)
+        return b
+    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
+    b = nthroot(big53(a), n)
+    return convert(Interval{T}, b)
+end 
diff --git a/test/ITF1788_tests/ITF1788_tests.jl b/test/ITF1788_tests/ITF1788_tests.jl
@@ -10,3 +10,4 @@ include("libieeep1788_tests_rev.jl")
 include("libieeep1788_tests_set.jl")
 include("mpfi.jl")
 include("fi_lib.jl")
+include("c-xsc.jl")