disallow negative numbers

Author: mcabbott

base/range.jl

@@ -1527,10 +1527,6 @@ julia> logrange(1f0, 32f0, 11)
 
 julia> logrange(1, 1000, length=4) ≈ 10 .^ (0:3)
 true
-
-julia> logrange(-27, -3, length=7)  # allows negative numbers
-7-element Base.LogRange{Float64, Base.TwicePrecision{Float64}}:
- -27.0, -18.7208, -12.9802, -9.0, -6.24025, -4.32675, -3.0
 ```
 
 See the [`LogRange`](@ref Base.LogRange) type for further details.
@@ -1555,18 +1551,15 @@ provided, but intermediate values may have small floating-point errors.
 These are calculated using the logs of the endpoints, which are
 stored on construction, often in higher precision than `T`.
 
-Negative values of `start` and `stop` are allowed, but both must have the
-same sign. All values are then negative.
-
 # Examples
 ```jldoctest
 julia> logrange(1, 4, length=5)
 5-element Base.LogRange{Float64, Base.TwicePrecision{Float64}}:
  1.0, 1.41421, 2.0, 2.82843, 4.0
 
-julia> Base.LogRange{Float16}(-1, -4, 5)
+julia> Base.LogRange{Float16}(1, 4, 5)
 5-element Base.LogRange{Float16, Float64}:
- -1.0, -1.414, -2.0, -2.828, -4.0
+ 1.0, 1.414, 2.0, 2.828, 4.0
 
 julia> logrange(1e-310, 1e-300, 11)[1:2:end]
 6-element Vector{Float64}:
@@ -1664,20 +1657,15 @@ struct LogRange{T<:Number,X} <: AbstractArray{T,1}
         elseif len == 1 && start != stop
             throw(ArgumentError(LazyString(
                 "LogRange(", start, ", ", stop, ", ", len, "): endpoints differ, while length is 1")))
-        elseif iszero(start) || iszero(stop)
-        elseif T <: Real && (start<0) ⊻ (stop<0)
+        elseif T <: Real && ((start<0) || (stop<0))
             throw(DomainError((start, stop),
                 "LogRange will only return complex results if called with a complex argument"))
         end
         if T <: Integer || T <: Complex{<:Integer}
             # LogRange{Int}(1, 512, 4) produces InexactError: Int64(7.999999999999998)
             throw(ArgumentError("LogRange{T} does not support integer types"))
         end
-        ex = if T <: Real && start + stop < 0  # start+stop allows for LogRange(-0.0, -2, 3)
-            _logrange_extra(-a, -b, len)
-        else
-            _logrange_extra(a, b, len)
-        end
+        ex = _logrange_extra(a, b, len)
         new{T,typeof(ex[1])}(a, b, len, ex)
     end
 end

test/ranges.jl

@@ -2612,7 +2612,6 @@ end
     @test logrange(1, 10^9, 19)[1:2:end] ≈ 10 .^ (0:9)
 
     # negative & complex
-    @test logrange(-1, -4, 3) == [-1, -2, -4]
     @test logrange(1, -1+0.0im, 3) ≈ [1, im, -1]  # branch cut first arg
     @test logrange(1, -1-0.0im, 3) ≈ [1, -im, -1]
     @test logrange(-1+1e-10im, 1, 3) ≈ [-1, im, 1]  # branch cut second arg
@@ -2628,10 +2627,8 @@ end
     @test logrange(nextfloat(0f0), floatmax(Float32), typemax(Int))[end] === floatmax(Float32)
     @test logrange(nextfloat(Float16(0)), floatmax(Float16), 66_000)[end] === floatmax(Float16)
     @test first(logrange(pi, 2pi, 3000)) === logrange(pi, 2pi, 3000)[1] === Float64(pi)
-    @test last(logrange(-0.01, -0.1, 3000)) === last(logrange(-0.01, -0.1, 3000))[end] === -0.1
     if Int == Int64
         @test logrange(0.1, 1000, 2^54)[end] === 1000.0
-        @test logrange(-0.1, -1000, 2^55)[end] === -1000.0
     end
 
     # empty, only, NaN, Inf
@@ -2645,18 +2642,12 @@ end
     @test isnan(logrange(1f0, NaN32, 3)[2])
     @test isnan(logrange(NaN32, 2f0, 3)[2])
     @test isnan(logrange(0, 2, 3)[1])
-    @test isnan(logrange(0, -2, 3)[1])
     @test isnan(logrange(-0.0, +2.0, 3)[1])
     @test isnan(logrange(0f0, 2f0, 3)[1])
-    @test isnan(logrange(0f0, -2f0, 3)[1])
-    @test isnan(logrange(-0f0, 2f0, 3)[1])
     @test isinf(logrange(1, Inf, 3)[2])
-    @test -Inf === logrange(-1, -Inf, 3)[2]
     @test isinf(logrange(1f0, Inf32, 3)[2])
-    @test -Inf32 === logrange(-1f0, -Inf32, 3)[2]
     # constant
     @test logrange(1, 1, 3) == fill(1.0, 3)
-    @test logrange(-1f0, -1f0, 3) == fill(-1f0, 3)
     @test all(isnan, logrange(0.0, -0.0, 3))
     @test all(isnan, logrange(-0f0, 0f0, 3))
 
@@ -2684,6 +2675,7 @@ end
     @test_throws ArgumentError logrange(1, 10, -1)  # negative length
     @test_throws ArgumentError logrange(1, 10, 1) # endpoints must not differ
     @test_throws DomainError logrange(1, -1, 3)   # needs complex numbers
+    @test_throws DomainError logrange(-1, -2, 3)  # not supported, for now
     @test_throws ArgumentError logrange(1, 10, 2)[true]  # bad index
     @test_throws BoundsError logrange(1, 10, 2)[3]
     @test_throws ArgumentError Base.LogRange{Int}(1,4,5)  # no integer ranges