Fixed rounding such that it doesn't overflow in edge cases. Also adde…

…d tests. Fixes JuliaLang#15215.
pkofod · Feb 24, 2016 · 1c7da9a · tkelman · Feb 25, 2016 · 1c7da9a
1 parent f5338c8
commit 1c7da9a
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Showing 2 changed files with 19 additions and 9 deletions.
diff --git a/base/rational.jl b/base/rational.jl
@@ -290,18 +290,18 @@ ceil{ T}(::Type{T}, x::Rational) = convert(T,cld(x.num,x.den))
 
 function round{T}(::Type{T}, x::Rational, ::RoundingMode{:Nearest})
     q,r = divrem(x.num,x.den)
-    s = abs(r) < (x.den+one(x.den)+iseven(q))>>1 ? q : q+copysign(one(q),x.num)
+    s = abs(r) < abs((x.den-copysign(typeof(x.den)(4), x.num)+one(x.den)+iseven(q))>>1 + copysign(typeof(x.den)(2), x.num)) ? q : q+copysign(one(q),x.num)
     convert(T,s)
 end
 round{T}(::Type{T}, x::Rational) = round(T,x,RoundNearest)
 function round{T}(::Type{T}, x::Rational, ::RoundingMode{:NearestTiesAway})
     q,r = divrem(x.num,x.den)
-    s = abs(r) < (x.den+one(x.den))>>1 ? q : q+copysign(one(q),x.num)
+    s = abs(r) < abs((x.den-copysign(typeof(x.den)(4), x.num)+one(x.den))>>1 + copysign(typeof(x.den)(2), x.num)) ? q : q+copysign(one(q),x.num)
     convert(T,s)
 end
 function round{T}(::Type{T}, x::Rational, ::RoundingMode{:NearestTiesUp})
     q,r = divrem(x.num,x.den)
-    s = abs(r) < (x.den+one(x.den)+(x.num<0))>>1 ? q : q+copysign(one(q),x.num)
+    s = abs(r) < abs((x.den-copysign(typeof(x.den)(4), x.num)+one(x.den)+(x.num<0))>>1 + copysign(typeof(x.den)(2), x.num)) ? q : q+copysign(one(q),x.num)
     convert(T,s)
 end
 

diff --git a/test/numbers.jl b/test/numbers.jl
@@ -2782,12 +2782,12 @@ for Tf = (Float16, Float32, Float64), Ti = (Int16, Int32, Int64)
     @test round(Tf, Rational(1,2), RoundNearestTiesUp) == 1.0
     @test round(Tf, Rational(1,2), RoundNearestTiesAway) == 1.0
 
-   # @test round( almost_half) == 0//1
-   # @test round(-almost_half) == 0//1
-   # @test round(Tf,  almost_half, RoundNearestTiesUp) == 0.0
-   # @test round(Tf, -almost_half, RoundNearestTiesUp) == 0.0
-   # @test round(Tf,  almost_half, RoundNearestTiesAway) == 0.0
-   # @test round(Tf, -almost_half, RoundNearestTiesAway) == 0.0
+    @test round( almost_half) == 0//1
+    @test round(-almost_half) == 0//1
+    @test round(Tf,  almost_half, RoundNearestTiesUp) == 0.0
+    @test round(Tf, -almost_half, RoundNearestTiesUp) == 0.0
+    @test round(Tf,  almost_half, RoundNearestTiesAway) == 0.0
+    @test round(Tf, -almost_half, RoundNearestTiesAway) == 0.0
 
     @test round( exactly_half) == 0//1 # rounds to closest _even_ integer
     @test round(-exactly_half) == 0//1 # rounds to closest _even_ integer
@@ -2803,6 +2803,11 @@ for Tf = (Float16, Float32, Float64), Ti = (Int16, Int32, Int64)
     @test round(Tf,  over_half, RoundNearestTiesAway) == 1.0
     @test round(Tf, -over_half, RoundNearestTiesUp) == -1.0
     @test round(Tf, -over_half, RoundNearestTiesAway) == -1.0
+
+    @test round(Tf, 11//2, RoundNearestTiesUp) == 6.0
+    @test round(Tf, -11//2, RoundNearestTiesUp) == -5.0
+    @test round(Tf, 11//2, RoundNearestTiesAway) == 6.0
+    @test round(Tf, -11//2, RoundNearestTiesAway) == -6.0
 end
 
 let
@@ -2823,3 +2828,8 @@ let
         @test read(io2, typeof(rational2)) == rational2
     end
 end
+
+@test round(11//2) == 6 # rounds to closest _even_ integer
+@test round(-11//2) == -6 # rounds to closest _even_ integer
+@test round(11//3) == 4 # rounds to closest _even_ integer
+@test round(-11//3) == -4 # rounds to closest _even_ integer