Add round (#44)

Author: jmkuhn

src/DecFP.jl

@@ -184,6 +184,8 @@ for w in (32,64,128)
                 Base.trunc(::Type{$Ti′}, x::$BID) = xchk(ccall(($(bidsym(w,"to_",lowercase(i′),"_xint")), libbid), $Ti′, ($BID,), x), InexactError, INVALID | OVERFLOW)
                 Base.floor(::Type{$Ti′}, x::$BID) = xchk(ccall(($(bidsym(w,"to_",lowercase(i′),"_xfloor")), libbid), $Ti′, ($BID,), x), InexactError, INVALID | OVERFLOW)
                 Base.ceil(::Type{$Ti′}, x::$BID) = xchk(ccall(($(bidsym(w,"to_",lowercase(i′),"_xceil")), libbid), $Ti′, ($BID,), x), InexactError, INVALID | OVERFLOW)
+                Base.round(::Type{$Ti′}, x::$BID) = xchk(ccall(($(bidsym(w,"to_",lowercase(i′),"_xrnint")), libbid), $Ti′, ($BID,), x), InexactError, INVALID | OVERFLOW)
+                Base.round(::Type{$Ti′}, x::$BID, ::RoundingMode{:NearestTiesAway}) = xchk(ccall(($(bidsym(w,"to_",lowercase(i′),"_xrninta")), libbid), $Ti′, ($BID,), x), InexactError, INVALID | OVERFLOW)
                 Base.convert(::Type{$Ti′}, x::$BID) = xchk(ccall(($(bidsym(w,"to_",lowercase(i′),"_xfloor")), libbid), $Ti′, ($BID,), x), InexactError)
             end
         end
@@ -197,8 +199,20 @@ end # widths w
 Base.trunc(::Type{Integer}, x::DecimalFloatingPoint) = trunc(Int, x)
 Base.floor(::Type{Integer}, x::DecimalFloatingPoint) = floor(Int, x)
 Base.ceil(::Type{Integer}, x::DecimalFloatingPoint) = ceil(Int, x)
+Base.round(::Type{Integer}, x::DecimalFloatingPoint) = round(Int, x)
+Base.round(::Type{Integer}, x::DecimalFloatingPoint, ::RoundingMode{:NearestTiesAway}) = round(Int, x, RoundNearestTiesAway)
 Base.convert(::Type{Integer}, x::DecimalFloatingPoint) = convert(Int, x)
 
+Base.round{T<:Integer}(::Type{T}, x::DecimalFloatingPoint, ::RoundingMode{:Nearest}) = round(T, x)
+function Base.round{T<:Integer}(::Type{T}, x::DecimalFloatingPoint, ::RoundingMode{:NearestTiesUp})
+    y = floor(T, x)
+    ifelse(x==y, y, copysign(floor(T, 2*x-y), x))
+end
+Base.round{T<:Integer}(::Type{T}, x::DecimalFloatingPoint, ::RoundingMode{:ToZero}) = trunc(T, x)
+Base.round{T<:Integer}(::Type{T}, x::DecimalFloatingPoint, ::RoundingMode{:FromZero}) = (x>=0 ? ceil(T, x) : floor(T, x))
+Base.round{T<:Integer}(::Type{T}, x::DecimalFloatingPoint, ::RoundingMode{:Up}) = ceil(T, x)
+Base.round{T<:Integer}(::Type{T}, x::DecimalFloatingPoint, ::RoundingMode{:Down}) = floor(T, x)
+
 # the complex-sqrt function in base doesn't work for use, because it requires base-2 ldexp
 function Base.sqrt{T<:DecimalFloatingPoint}(z::Complex{T})
     x, y = reim(z)

test/runtests.jl

@@ -85,7 +85,11 @@ for T in (Dec32, Dec64, Dec128)
         if Ti != Integer
             @test parse(T, "17") == T(Ti(17)) == Ti(17) == Ti(T(17))
         end
-        @test trunc(Ti, T(4.5)) == floor(Ti, T(4.5)) == 4 == ceil(Ti, T(4.5)) - 1
+        @test trunc(Ti, T(2.7)) === floor(Ti, T(2.7)) === round(Ti, T(2.7), RoundDown) === round(Ti, T(2.7), RoundToZero) === Ti(2)
+        @test ceil(Ti, T(2.3)) === round(Ti, T(2.3), RoundUp) === round(Ti, T(2.3), RoundFromZero) === Ti(3)
+        @test round(Ti, T(1.5)) === round(Ti, T(2.5)) === round(Ti, T(1.5), RoundNearest) === round(Ti, T(2.5), RoundNearest) === Ti(2)
+        @test round(Ti, T(2.5), RoundNearestTiesAway) === round(Ti, T(3.3), RoundNearestTiesAway) === Ti(3)
+        @test round(Ti, T(2.5), RoundNearestTiesUp) === round(Ti, T(3.3), RoundNearestTiesUp) === Ti(3)
         @test_throws InexactError convert(Ti, xd)
         @test_throws InexactError trunc(Ti, realmax(T))
         @test_throws InexactError floor(Ti, realmax(T))
@@ -94,7 +98,12 @@ for T in (Dec32, Dec64, Dec128)
             @test parse(T, "-17") == T(Ti(-17)) == Ti(-17) == Ti(T(-17))
         end
         if Ti <: Signed || Ti === Integer
-            @test floor(Ti, T(-4.5)) == -5 == trunc(Ti, T(-4.5)) - 1 == ceil(Ti, T(-4.5)) - 1
+            @test trunc(Ti, T(-2.7)) === round(Ti, T(-2.7), RoundToZero) === Ti(-2)
+            @test floor(Ti, T(-2.3)) === round(Ti, T(-2.3), RoundDown) === round(Ti, T(-2.3), RoundFromZero) === Ti(-3)
+            @test ceil(Ti, T(-2.7)) === round(Ti, T(-2.7), RoundUp) === Ti(-2)
+            @test round(Ti, T(-1.5)) === round(Ti, T(-2.5)) === round(Ti, T(-1.5), RoundNearest) === round(Ti, T(-2.5), RoundNearest) === Ti(-2)
+            @test round(Ti, T(-2.5), RoundNearestTiesAway) === round(Ti, T(-3.3), RoundNearestTiesAway) === Ti(-3)
+            @test round(Ti, T(-1.5), RoundNearestTiesUp) === round(Ti, T(-0.7), RoundNearestTiesUp) === Ti(-1)
             @test_throws InexactError convert(Ti, yd)
         end
     end