Convert from Rational to FD must be exact

Author: omus

src/FixedPointDecimals.jl

@@ -211,12 +211,8 @@ end
 convert{T <: FD}(::Type{T}, x::AbstractFloat) = round(T, x)
 
 function convert{T, f}(::Type{FD{T, f}}, x::Rational)::FD{T, f}
-    powt = T(10)^f
-    num::T, den::T = numerator(x), denominator(x)
-    g = gcd(powt, den)
-    powt = div(powt, g)
-    den = div(den, g)
-    reinterpret(FD{T, f}, powt * num) / FD{T, f}(den)
+    powt = coefficient(FD{T, f})
+    reinterpret(FD{T, f}, T(x * powt))
 end
 
 function convert{T, f, U, g}(::Type{FD{T, f}}, x::FD{U, g})

test/runtests.jl

@@ -116,10 +116,13 @@ end
         @test min_int >= typemin(T)
         @test value(convert(FD{T,f}, min_int / powt)) == min_int
 
+        @test convert(FD{T,f}, typemax(T) // powt) == reinterpret(FD{T,f}, typemax(T))
+        @test convert(FD{T,f}, typemin(T) // powt) == reinterpret(FD{T,f}, typemin(T))
+
         @test_throws InexactError convert(FD{T,f}, T(1))
 
         # Adjust number of decimal places allowed so we can have `-10 < x < 10` where x is
-        # a FD{T,f}.
+        # a FD{T,f}. Only needed to test `convert(::FD, ::Integer)`
         f = FixedPointDecimals.max_exp10(T)
         powt = FixedPointDecimals.coefficient(FD{T,f})
 
@@ -136,6 +139,8 @@ end
     @test_throws InexactError convert(FD2, FD4(0.0001))
     @test_throws InexactError convert(FD4, typemax(FD2))
     @test_throws InexactError convert(SFD2, typemax(FD2))
+    @test_throws InexactError convert(FD2, 1//3)
+    @test_throws InexactError convert(FD{Int8,1}, 1//4)
 end
 
 @testset "promotion" begin