added support for an arbitrary number of fraction bits

Author: bjarthur

README.md

@@ -15,21 +15,29 @@ used like any other number: they can be added, multiplied, raised to a power,
 etc. In many cases these operations result in conversion to floating-point types.
 
 # Type hierarchy
-This library defines an abstract type `FixedPoint{T <: Integer, f}` as a subtype of `Real`. The parameter `T` is the underlying representation and `f` is the number of fraction bits.
-
-For signed integers, there is a fixed-point type `Fixed{T, f}` and for unsigned integers, there is the `UFixed{T, f}` type.
-
-These types, built with `f` fraction bits, map the closed interval [0.0,1.0]
-to the span of numbers with `f` bits.
-For example, the `UFixed8` type is represented internally by a `UInt8`, and makes
-`0x00` equivalent to `0.0` and `0xff` to `1.0`.
-The types `UFixed10`, `UFixed12`, `UFixed14`, and `UFixed16` are all based on `UInt16`
-and reach the value `1.0` at 10, 12, 14, and 16 bits, respectively (`0x03ff`, `0x0fff`,
-`0x3fff`, and `0xffff`).
-
-To construct such a number, use `convert(UFixed12, 1.3)`, `ufixed12(1.3)`, or the literal syntax `0x14ccuf12`.
-The latter syntax means to construct a `UFixed12` (it ends in `uf12`) from the `UInt16` value
-`0x14cc`.
+This library defines an abstract type `FixedPoint{T <: Integer, f}` as a
+subtype of `Real`. The parameter `T` is the underlying representation and `f`
+is the number of fraction bits.
+
+For signed integers, there is a fixed-point type `Fixed{T, f}` and for unsigned
+integers, there is the `UFixed{T, f}` type.
+
+These types, built with `f` fraction bits, map the closed interval [0.0,1.0] to
+the span of numbers with `f` bits.  For example, the `UFixed8` type (aliased to
+UFixed{UInt8,8}) is represented internally by a `UInt8`, and makes `0x00`
+equivalent to `0.0` and `0xff` to `1.0`.  The type aliases `UFixed10`, `UFixed12`,
+`UFixed14`, and `UFixed16` are all based on `UInt16` and reach the value `1.0`
+at 10, 12, 14, and 16 bits, respectively (`0x03ff`, `0x0fff`, `0x3fff`, and
+`0xffff`).
+
+To construct such a number, use `convert(UFixed12, 1.3)`, `ufixed12(1.3)` (a
+convenience function), `UFixed{UInt16,12}`, or the literal syntax `0x14ccuf12`.
+The latter syntax means to construct a `UFixed12` (it ends in `uf12`) from the
+`UInt16` value `0x14cc`.
+
+More generally, an arbitrary number of bits from any of the standard unsigned
+integer widths can be used for the fractional part.  For example:
+`UFixed{UInt32,16}`, `UFixed{UInt64,3}`, `UFixed{UInt128,7}`.
 
 There currently is no literal syntax for signed `Fixed` numbers. 
 

src/FixedPointNumbers.jl

@@ -90,4 +90,14 @@ scaledual{T<:FixedPoint}(Tdual::Type, x::Union{T,AbstractArray{T}}) =
 scaledual{Tdual<:Number, T<:FixedPoint}(b::Tdual, x::Union{T,AbstractArray{T}}) =
     convert(Tdual, b/one(T)), reinterpret(rawtype(T), x)
 
+# Show
+function show{T<:FixedPoint}(io::IO, x::T)
+    print(io, typeof(x))
+    print(io, "(")
+    showcompact(io, x)
+    print(io, ")")
+end
+const _log2_10 = 3.321928094887362
+showcompact{T,f}(io::IO, x::UFixed{T,f}) = show(io, round(convert(Float64,x), ceil(Int,f/_log2_10)))
+
 end # module

src/fixed.jl

@@ -54,13 +54,3 @@ promote_rule{T,f,TR}(::Type{Fixed{T,f}}, ::Type{Rational{TR}}) = Rational{TR}
 
 # TODO: Document and check that it still does the right thing.
 decompose{T,f}(x::Fixed{T,f}) = x.i, -f, 1
-
-# printing
-function show(io::IO, x::Fixed)
-    print(io, typeof(x))
-    print(io, "(")
-    showcompact(io, x)
-    print(io, ")")
-end
-const _log2_10 = 3.321928094887362
-showcompact{T,f}(io::IO, x::Fixed{T,f}) = show(io, round(convert(Float64,x), ceil(Int,f/_log2_10)))

src/ufixed.jl

@@ -19,11 +19,7 @@ typealias UFixed16 UFixed{UInt16,16}
 
 const UF = (UFixed8, UFixed10, UFixed12, UFixed14, UFixed16)
 
-for (uf) in UF
-    T = rawtype(uf)
-    f = nbitsfrac(uf)
-    @eval reinterpret(::Type{UFixed{$T,$f}}, x::$T) = UFixed{$T,$f}(x, 0)
-end
+reinterpret{T<:Unsigned, f}(::Type{UFixed{T,f}}, x::T) = UFixed{T,f}(x, 0)
 
 # The next lines mimic the floating-point literal syntax "3.2f0"
 immutable UFixedConstructor{T,f} end
@@ -35,14 +31,7 @@ const uf14 = UFixedConstructor{UInt16,14}()
 const uf16 = UFixedConstructor{UInt16,16}()
 
 zero{T,f}(::Type{UFixed{T,f}}) = UFixed{T,f}(zero(T),0)
-for uf in UF
-    TT = rawtype(uf)
-    f = nbitsfrac(uf)
-    T = UFixed{TT,f}
-    @eval begin
-        one(::Type{$T}) = $T($(2^f-1),0)
-    end
-end
+one{T<:UFixed}(::Type{T}) = T((2^nbitsfrac(T)-1),0)
 zero(x::UFixed) = zero(typeof(x))
  one(x::UFixed) =  one(typeof(x))
 rawone(v) = reinterpret(one(v))
@@ -95,15 +84,21 @@ abs(x::UFixed) = x
 # Functions
 trunc{T<:UFixed}(x::T) = T(div(reinterpret(x), rawone(T))*rawone(T),0)
 floor{T<:UFixed}(x::T) = trunc(x)
-for T in UF
-    f = nbitsfrac(T)
-    R = rawtype(T)
-    roundmask = convert(R, 1<<(f-1))
-    k = 8*sizeof(R)-f
-    ceilmask  = (typemax(R)<<k)>>k
-    @eval begin
-        round(x::$T) = (y = trunc(x); return convert(rawtype($T), reinterpret(x)-reinterpret(y))&$roundmask>0 ? $T(y+one($T)) : y)
-         ceil(x::$T) = (y = trunc(x); return convert(rawtype($T), reinterpret(x)-reinterpret(y))&$ceilmask >0 ? $T(y+one($T)) : y)
+@generated function round{T,f}(x::UFixed{T,f})
+    mask = convert(T, 1<<(f-1))
+    quote
+        y = trunc(x)
+        return convert(T, reinterpret(x)-reinterpret(y)) & $mask>0 ?
+                UFixed{T,f}(y+one(UFixed{T,f})) : y
+    end
+end
+@generated function ceil{T,f}(x::UFixed{T,f})
+    k = 8*sizeof(T)-f
+    mask = (typemax(T)<<k)>>k
+    quote
+        y = trunc(x)
+        return convert(T, reinterpret(x)-reinterpret(y)) & ($mask)>0 ?
+                UFixed{T,f}(y+one(UFixed{T,f})) : y
     end
 end
 
@@ -152,25 +147,8 @@ function decompose(x::UFixed)
 end
 
 # Promotions
-for T in UF
-    @eval begin
-        promote_rule(::Type{$T}, ::Type{Float32}) = Float32
-        promote_rule(::Type{$T}, ::Type{Float64}) = Float64
-        promote_rule{TR<:Rational}(::Type{$T}, ::Type{TR}) = TR
-    end
-    for Ti in (Int8, UInt8, Int16, UInt16, Int32, UInt32, Int64, UInt64)
-        Tp = eps(convert(Float32, typemax(Ti))) > eps(T) ? Float64 : Float32
-        @eval begin
-            promote_rule(::Type{$T}, ::Type{$Ti}) = $Tp
-        end
-    end
-end
-
-# Show
-function show{T,f}(io::IO, x::UFixed{T,f})
-    print(io, "UFixed", f)
-    print(io, "(")
-    showcompact(io, x)
-    print(io, ")")
-end
-showcompact{T,f}(io::IO, x::UFixed{T,f}) = show(io, round(convert(Float64,x), ceil(Int,f/_log2_10)))
+promote_rule{T<:UFixed}(::Type{T}, ::Type{Float32}) = Float32
+promote_rule{T<:UFixed}(::Type{T}, ::Type{Float64}) = Float64
+promote_rule{T<:UFixed, R<:Rational}(::Type{T}, ::Type{R}) = R
+promote_rule{T<:UFixed, Ti<:Union{Signed,Unsigned}}(::Type{T}, ::Type{Ti}) =
+        eps(convert(Float32, typemax(Ti))) > eps(T) ? Float64 : Float32

test/ufixed.jl

@@ -17,14 +17,16 @@ using FixedPointNumbers, Base.Test
 @test ufixed14(1.0) == 0x3fffuf14
 @test ufixed12([2]) == UFixed12[0x1ffeuf12]
 
-for T in FixedPointNumbers.UF
+UF2 = (UFixed{UInt32,16}, UFixed{UInt64,3}, UFixed{UInt128,7})
+
+for T in (FixedPointNumbers.UF..., UF2...)
     @test zero(T) == 0
     @test one(T) == 1
     @test one(T) * one(T) == one(T)
     @test typemin(T) == 0
     @test realmin(T) == 0
     @test eps(zero(T)) == eps(typemax(T))
-    @test sizeof(T) == 1 + (T != UFixed8)
+    @test sizeof(T) == sizeof(FixedPointNumbers.rawtype(T))
 end
 @test typemax(UFixed8) == 1
 @test typemax(UFixed10) == typemax(UInt16)//(2^10-1)
@@ -34,6 +36,7 @@ end
 @test typemax(UFixed10) == typemax(UInt16) // (2^10-1)
 @test typemax(UFixed12) == typemax(UInt16) // (2^12-1)
 @test typemax(UFixed14) == typemax(UInt16) // (2^14-1)
+@test typemax(UFixed{UInt32,16}) == typemax(UInt32) // (2^16-1)
 
 x = UFixed8(0.5)
 @test isfinite(x) == true
@@ -45,13 +48,14 @@ x = UFixed8(0.5)
 @test convert(UFixed12, 1.1/typemax(UInt16)*16) == eps(UFixed12)
 @test convert(UFixed14, 1.1/typemax(UInt16)*4)  == eps(UFixed14)
 @test convert(UFixed16, 1.1/typemax(UInt16))    == eps(UFixed16)
+@test convert(UFixed{UInt32,16}, 1.1/typemax(UInt32)*2^16)    == eps(UFixed{UInt32,16})
 
 @test convert(UFixed8,  1.1f0/typemax(UInt8)) == eps(UFixed8)
 
 @test convert(Float64, eps(UFixed8)) == 1/typemax(UInt8)
 @test convert(Float32, eps(UFixed8)) == 1.0f0/typemax(UInt8)
 @test convert(BigFloat, eps(UFixed8)) == BigFloat(1)/typemax(UInt8)
-for T in FixedPointNumbers.UF
+for T in (FixedPointNumbers.UF..., UF2...)
     @test convert(Bool, zero(T)) == false
     @test convert(Bool, one(T))  == true
     @test convert(Bool, convert(T, 0.2)) == true
@@ -64,7 +68,7 @@ x = UFixed8(0b01010001, 0)
 @test ~x == UFixed8(0b10101110, 0)
 @test -x == 0xafuf8
 
-for T in FixedPointNumbers.UF
+for T in (FixedPointNumbers.UF..., UF2...)
     x = T(0x10,0)
     y = T(0x25,0)
     fx = convert(Float32, x)
@@ -89,7 +93,7 @@ function testtrunc{T}(inc::T)
     incf = convert(Float64, inc)
     tm = reinterpret(typemax(T))/reinterpret(one(T))
     x = zero(T)
-    for i = 0:reinterpret(typemax(T))-1
+    for i = 0 : min(1e6, reinterpret(typemax(T))-1)
         xf = incf*i
         try
             @test trunc(x) == trunc(xf)
@@ -113,7 +117,7 @@ function testtrunc{T}(inc::T)
     end
 end
 
-for T in FixedPointNumbers.UF
+for T in (FixedPointNumbers.UF..., UF2...)
     testtrunc(eps(T))
 end
 
@@ -122,7 +126,7 @@ x = 0xaauf8
 iob = IOBuffer()
 show(iob, x)
 str = takebuf_string(iob)
-@test startswith(str, "UFixed8(")
+@test startswith(str, "FixedPointNumbers.UFixed{UInt8,8}(")
 @test eval(parse(str)) == x
 
 # scaledual