Fix rounding in division (#100)

Author: barucden

src/arithmetic.jl

@@ -201,12 +201,18 @@ function Base.:(/)(x::Decimal, y::Decimal)
 
     if d > 0
         # If `d` is positive, we take the path denoted (P1)
-        c = div(x.c * BigTen^d, y.c)
+        c, rem = divrem(x.c * BigTen^d, y.c)
     elseif d < 0
         # If `d` is negative, we take the path denoted (P2)
-        c = div(x.c, y.c * BigTen^(-d))
+        c, rem = divrem(x.c, y.c * BigTen^(-d))
     else
-        c = div(x.c, y.c)
+        c, rem = divrem(x.c, y.c)
+    end
+
+    # When the result is non-exact, and the last coefficient digit is 5, we
+    # need to increment the coefficient for correct rounding
+    if rem > 0 && isdivisible(c, 5)
+        c += 1
     end
 
     return fix(Decimal(s, c, q))

test/test_arithmetic.jl

@@ -73,4 +73,7 @@ using Test
     @with_context (Emax=999, Emin=-999, precision=9, rounding=RoundNearestTiesAway) @test inv(dec"2") == dec"0.5"
 end
 
+Decimals.@with_context (precision=2, rounding=RoundNearest) @test dec"10500000" / dec"10000" == Decimal(0, 10, 2)
+Decimals.@with_context (precision=2, rounding=RoundNearest) @test dec"10500009" / dec"10000" == Decimal(0, 11, 2)
+
 end