linspace: handle very large *and* very small endpoints correctly.

base/range.jl

@@ -193,17 +193,23 @@ function linspace{T<:FloatingPoint}(start::T, stop::T, len::Int)
             e = lcm(b,d)
             a *= div(e,b)
             c *= div(e,d)
-            s, p = frexp(convert(T,n*e))
-            p = one(p) << p
-            a /= p; c /= p
+            s = convert(T,n*e)
+            if isinf(a*n) || isinf(c*n)
+                s, p = frexp(convert(T,s))
+                p = one(p) << p
+                a /= p; c /= p
+            end
             if a*n/s == start && c*n/s == stop
                 return LinSpace(a, c, len, s)
             end
         end
     end
-    s, p = frexp(convert(T,n))
-    p = one(p) << p
-    start /= p; stop /= p
+    s = convert(T,n)
+    if isinf(s*start) || isinf(s*stop)
+        s, p = frexp(s)
+        p = one(p) << p
+        start /= p; stop /= p
+    end
     return LinSpace(start, stop, len, s)
 end
 linspace(start::Real, stop::Real, len::Real=50) =

test/ranges.jl

@@ -286,6 +286,27 @@ for T = (Float32, Float64,),# BigFloat),
     @test [r[n:-2:1];] == [r;][n:-2:1]
 end
 
+# very small linspace & ranges
+for T = (Float32, Float64)
+    z = zero(T)
+    u = eps(z)
+    @test [linspace(-u,u,2);] == [-u,u]
+    @test [linspace(-u,u,3);] == [-u,0,u]
+    @test [linspace(-u,u,4);] == [-u,0,0,u]
+    @test [linspace(-u,u,4);][2] === -z
+    @test [linspace(-u,u,4);][3] === z
+    @test [linspace(u,-u,2);] == [u,-u]
+    @test [linspace(u,-u,3);] == [u,0,-u]
+    @test [linspace(u,-u,4);] == [u,0,0,-u]
+    @test [linspace(u,-u,4);][2] === z
+    @test [linspace(u,-u,4);][3] === -z
+    v = [linspace(-u,u,12);]
+    @test length(v) == 12
+    @test issorted(v) && unique(v) == [-u,0,0,u]
+    @test [-3u:u:3u;] == [linspace(-3u,3u,7);] == [-3:3;].*u
+    @test [3u:-u:-3u;] == [linspace(3u,-3u,7);] == [3:-1:-3;].*u
+end
+
 # near-equal ranges
 @test 0.0:0.1:1.0 != 0.0f0:0.1f0:1.0f0