add mid radius inf sup diam for reals (#511)

Author: lucaferranti

Project.toml

@@ -1,7 +1,7 @@
 name = "IntervalArithmetic"
 uuid = "d1acc4aa-44c8-5952-acd4-ba5d80a2a253"
 repo = "https://github.com/JuliaIntervals/IntervalArithmetic.jl.git"
-version = "0.20.4"
+version = "0.20.5"
 
 [deps]
 CRlibm = "96374032-68de-5a5b-8d9e-752f78720389"

src/intervals/arithmetic.jl

@@ -305,6 +305,8 @@ end
 inf(a::Interval) = ifelse(iszero(a.lo) && !signbit(a.lo), copysign(a.lo, -1), a.lo)
 sup(a::Interval) = a.hi
 
+inf(a::Real) = a
+sup(a::Real) = a
 
 ## Functions needed for generic linear algebra routines to work
 real(a::Interval) = a
@@ -512,6 +514,10 @@ function radius(a::Interval{Rational{T}}) where T
     return max(m - a.lo, a.hi - m)
 end
 
+mid(a::Real) = a
+diam(a::Real) = zero(a)
+radius(a::Real) = zero(a)
+
 # cancelplus and cancelminus
 """
     cancelminus(a, b)

test/interval_tests/consistency.jl

@@ -186,6 +186,9 @@ setprecision(Interval, Float64)
         @test inf(entireinterval(a)) == -Inf
         @test sup(entireinterval(a)) == Inf
         @test isnan(sup(nai(BigFloat)))
+
+        @test inf(2.5) == 2.5
+        @test sup(2.5) == 2.5
     end
 
     @testset "mid" begin
@@ -220,6 +223,8 @@ setprecision(Interval, Float64)
         @test diam( @interval(0.1) ) == eps(0.1)
         @test isnan(diam(emptyinterval()))
         @test diam(a) == 1.0000000000000002
+
+        @test diam(0.1) == 0
     end
 
     @testset "mig and mag" begin
@@ -286,6 +291,9 @@ setprecision(Interval, Float64)
         else
             @test_throws InexactError nai(Interval(1//2))
         end
+
+        @test mid(2.125) == 2.125
+        @test radius(2.125) == 0
     end
 
     @testset "abs, min, max, sign" begin