Add ispositive, etc.

base/exports.jl

@@ -295,7 +295,9 @@ export
     isinf,
     isinteger,
     isnan,
+    isnegative,
     isodd,
+    ispositive,
     ispow2,
     isqrt,
     isreal,

base/floatfuncs.jl

@@ -16,6 +16,9 @@ signbit(x::Float64) = signbit(bitcast(Int64, x))
 signbit(x::Float32) = signbit(bitcast(Int32, x))
 signbit(x::Float16) = signbit(bitcast(Int16, x))
 
+ispositive(x::IEEEFloat) = x>0
+isnegative(x::IEEEFloat) = x<0
+
 """
     maxintfloat(T=Float64)
 

base/number.jl

@@ -136,6 +136,45 @@ true
 """
 signbit(x::Real) = x < 0
 
+"""
+    ispositive(x)
+
+Test whether `x` is positive. Falls back to [`isnan`](@ref), [`signbit`](@ref) and [`iszero`](@ref). See also [`isnegative`](@ref).
+
+# Examples
+```jldoctest
+julia> ispositive(-4.0)
+false
+
+julia> ispositive(99)
+true
+
+julia> ispositive(0.0)
+false
+```
+"""
+ispositive(x) = !isnan(x) && !signbit(x) && !iszero(x)
+
+"""
+    isnegative(x)
+
+Test whether `x` is positive. Falls back to [`isnan`](@ref), [`signbit`](@ref) and [`iszero`](@ref). See also [`ispositive`](@ref).
+
+# Examples
+```jldoctest
+julia> isnegative(-4.0)
+true
+
+julia> isnegative(99)
+false
+
+julia> isnegative(-0.0)
+false
+```
+"""
+isnegative(x) = !isnan(x) && signbit(x) && !iszero(x)
+isnegative(x::Integer) = signbit(x) # skip iszero
+
 """
     sign(x)
 

test/numbers.jl

@@ -830,6 +830,54 @@ end
     @test cmp(isless, 1, NaN) == -1
     @test cmp(isless, NaN, NaN) == 0
 end
+@testset "ispositive/isnegative" begin
+    for T in Base.uniontypes(Base.IEEEFloat)
+        @test ispositive(one(T))
+        @test !ispositive(zero(T))
+        @test !ispositive(-zero(T))
+        @test !ispositive(-one(T))
+        @test !isnegative(one(T))
+        @test !isnegative(zero(T))
+        @test !isnegative(-zero(T))
+        @test isnegative(-one(T))
+        @test ispositive(T(Inf))
+        @test !ispositive(T(-Inf))
+        @test !ispositive(T(NaN))
+        @test !ispositive(T(-NaN))
+    end
+
+    for T in Base.BitSigned_types
+        @test ispositive(one(T))
+        @test !ispositive(zero(T))
+        @test !ispositive(-one(T))
+        @test !isnegative(one(T))
+        @test !isnegative(zero(T))
+        @test isnegative(-one(T))
+    end
+
+    for T in Base.BitUnsigned_types
+        @test ispositive(one(T))
+        @test !ispositive(zero(T))
+        @test ispositive(-one(T))
+        @test !isnegative(one(T))
+        @test !isnegative(zero(T))
+        @test !isnegative(-one(T))
+    end
+
+    @test ispositive(2//3)
+    @test !ispositive(-2//3)
+    @test !ispositive(0//1)
+    @test !ispositive(-0//1)
+    @test ispositive(1//0)
+    @test !ispositive(-1//0)
+
+    @test !isnegative(2//3)
+    @test isnegative(-2//3)
+    @test !isnegative(0//1)
+    @test !isnegative(-0//1)
+    @test !isnegative(1//0)
+    @test isnegative(-1//0)
+end
 @testset "Float vs Integer comparison" begin
     for x=-5:5, y=-5:5
         @test (x==y)==(Float64(x)==Int64(y))