Fix convert to Rational at the input limits

Author: omus

src/FixedPointDecimals.jl

@@ -253,8 +253,7 @@ function convert{TI <: Integer, T, f}(::Type{TI}, x::FD{T, f})::TI
     div(x.i, coefficient(FD{T, f}))
 end
 
-convert{TR<:Rational,T,f}(::Type{TR}, x::FD{T, f})::TR =
-    x.i // T(10)^f
+convert{TR <: Rational, T, f}(::Type{TR}, x::FD{T, f})::TR = x.i // coefficient(FD{T, f})
 
 promote_rule{T, f, TI <: Integer}(::Type{FD{T, f}}, ::Type{TI}) = FD{T, f}
 promote_rule{T, f, TF <: AbstractFloat}(::Type{FD{T, f}}, ::Type{TF}) = TF

test/runtests.jl

@@ -114,6 +114,11 @@ end
         @test convert(BigFloat, fd) == BigInt(val) / BigInt(powt)
     end
 
+    @testset "to rational" begin
+        fd = reinterpret(FD2, 25)
+        @test convert(Rational, fd) == 1//4
+    end
+
     @testset "invalid" begin
         @test_throws InexactError convert(FD2, FD4(0.0001))
         @test_throws InexactError convert(FD4, typemax(FD2))
@@ -154,6 +159,13 @@ end
         @test convert(Float64, fd)  == Float64(typemin(T) / powt)
         @test convert(BigFloat, fd) == BigInt(typemin(T)) / powt
 
+        # Converting to a rational
+        fd = reinterpret(FD{T,f}, typemax(T))
+        @test convert(Rational, fd)  == typemax(T) // powt
+
+        fd = reinterpret(FD{T,f}, typemin(T))
+        @test convert(Rational, fd)  == typemin(T) // powt
+
         # Adjust number of decimal places allowed so we can have `-10 < x < 10` where x is
         # a FD{T,f}. Only needed to test `convert(::FD, ::Integer)`
         f = FixedPointDecimals.max_exp10(T)