Fix show displaying wrong value

Author: omus

src/FixedPointDecimals.jl

@@ -283,7 +283,7 @@ function print{T, f}(io::IO, x::FD{T, f})
 
     # note: a is negative if x.i == typemin(x.i)
     s, a = sign(x.i), abs(x.i)
-    integer, fractional = divrem(a, T(10)^f)
+    integer, fractional = divrem(a, exp10(T, f))
     integer = abs(integer)  # ...but since f > 0, this is positive
     fractional = abs(fractional)
 
@@ -382,4 +382,15 @@ function parse_round{T}(::Type{T}, fractional::AbstractString, ::RoundingMode{:N
     return T(0)
 end
 
+function exp10_max{T}(::Type{T})
+    length(digits(typemax(T))) - 1
+end
+
+function exp10(T::Type, y::Integer)
+    while T != BigInt && exp10_max(T) < y
+        T = widen(T)
+    end
+    T(10)^y
+end
+
 end

test/runtests.jl

@@ -424,6 +424,12 @@ end
     @test string(FD2(-0.01)) == "-0.01"
     @test string(FD2(0)) == "0.00"
     @test string(FixedDecimal{Int,0}(123.4)) == "123"
+
+    # Displaying a decimal could be incorrect when using a decimal place precision which is
+    # close to or at the limit the limit for our storage type. Int32 for example can only
+    # store up to 10 digits of precision.
+    @test string(reinterpret(FD{Int32,10}, typemax(Int32))) ==  "0.2147483647"
+    @test string(reinterpret(FD{Int32,10}, typemin(Int32))) == "-0.2147483648"
 end
 
 @testset "show" begin