Improve constructor performance (#30)

Author: omus

src/FixedPointDecimals.jl

@@ -94,14 +94,20 @@ struct FixedDecimal{T <: Integer, f} <: Real
         if f >= 0 && (n < 0 || f <= n)
             new{T, f}(i % T)
         else
-            throw(ArgumentError(
-                "Requested number of decimal places $f exceeds the max allowed for the " *
-                "storage type $T: [0, $n]"
-            ))
+            # Note: introducing a function barrier to improve performance
+            # https://github.com/JuliaMath/FixedPointDecimals.jl/pull/30
+            _throw_storage_error(f, T, n)
         end
     end
 end
 
+@noinline function _throw_storage_error(f, T, n)
+    throw(ArgumentError(
+        "Requested number of decimal places $f exceeds the max allowed for the " *
+        "storage type $T: [0, $n]"
+    ))
+end
+
 const FD = FixedDecimal
 
 (::Type{T})(x::Real) where {T <: FD} = convert(T, x)
@@ -460,7 +466,6 @@ The highest value of `x` which does not result in an overflow when evaluating `T
 types of `T` that do not overflow -1 will be returned.
 """
 function max_exp10(::Type{T}) where {T <: Integer}
-    applicable(typemax, T) || return -1
     W = widen(T)
     type_max = W(typemax(T))
 
@@ -476,6 +481,8 @@ function max_exp10(::Type{T}) where {T <: Integer}
     exponent - 1
 end
 
+max_exp10(::Type{BigInt}) = -1
+
 """
     coefficient(::Type{FD{T, f}}) -> T
 

test/runtests.jl

@@ -109,6 +109,20 @@ end
         x = FixedPointDecimals.max_exp10(T)
         @test T(10)^x == widen(T(10))^x
     end
+
+    @testset "custom integer types" begin
+        @eval begin
+            primitive type Int24 <: Integer 24 end
+            Base.typemax(::Type{Int24}) = 2^24
+            Base.widen(::Type{Int24}) = Int32
+        end
+
+        @test FixedPointDecimals.max_exp10(Int24) == 7
+
+        # Note: we're just pretending that this is unbounded
+        @eval primitive type IntUnbounded <: Integer 256 end
+        @test_throws MethodError FixedPointDecimals.max_exp10(IntUnbounded)
+    end
 end
 
 # ensure that the coefficient multiplied by the highest and lowest representable values of