Thanks, that's something to look at.
On Wednesday, December 9, 2015 at 9:28:13 AM UTC-5, Eric Forgy wrote: > > How about this? > > > https://github.com/JuliaLang/julia/blob/2d821670d2516cd38b51710b07b3eb18f191cd1b/base/multimedia.jl > > > On Wednesday, December 9, 2015 at 10:22:06 PM UTC+8, milktrader wrote: >> >> I'd like a somewhat clever example (or boring one for that matter) that >> shows: >> >> 1. How to create an instance of a singleton type >> >> 2. How to write methods that use this type in a meaningful way. >> >> 3. How it's used in Base code (I seem to recall Void is a singleton type) >> >> On Wednesday, December 9, 2015 at 9:02:31 AM UTC-5, tshort wrote: >>> >>> I'm not sure what you want, either. How about this? >>> >>> julia> type BadInt{X} end >>> >>> julia> BadInt{3}() >>> BadInt{3}() >>> >>> julia> f{X}(::Type{BadInt{X}}, y) = X - y >>> f (generic function with 1 method) >>> >>> julia> f(BadInt{10}, 3) >>> 7 >>> >>> julia> f{X}(::BadInt{X}, y) = X - y >>> f (generic function with 2 methods) >>> >>> julia> f(BadInt{10}(), 3) >>> 7 >>> >>> >>> On Wed, Dec 9, 2015 at 8:56 AM, Eric Forgy <eric....@gmail.com> wrote: >>> >>>> Not sure I follow, but does this help? >>>> >>>> julia> type BadInt >>>> end >>>> >>>> julia> bi = BadInt() >>>> BadInt() >>>> >>>> julia> typeof(bi) >>>> BadInt >>>> >>>> >>>> On Wednesday, December 9, 2015 at 9:46:01 PM UTC+8, milktrader wrote: >>>>> >>>>> How do you create an instance of type BadInt then? >>>>> >>>>> On Wednesday, December 9, 2015 at 7:01:25 AM UTC-5, milktrader wrote: >>>>>> >>>>>> Trying to wrap my mind around singleton types to see if they might be >>>>>> useful for something I'm working on, but running into some confusion. >>>>>> Here >>>>>> is an example that I started working with: >>>>>> >>>>>> julia> type BadInt >>>>>> end >>>>>> >>>>>> julia> import Base.+ >>>>>> >>>>>> julia> +(x::BadInt, y::Int64) = x - y >>>>>> + (generic function with 172 methods) >>>>>> >>>>>> julia> BadInt() = 2 >>>>>> BadInt >>>>>> >>>>>> julia> BadInt + 2 >>>>>> ERROR: MethodError: `+` has no method matching +(::Type{BadInt}, >>>>>> ::Int64) >>>>>> Closest candidates are: >>>>>> +(::Any, ::Any, ::Any, ::Any...) >>>>>> +(::Int64, ::Int64) >>>>>> +(::Complex{Bool}, ::Real) >>>>>> ... >>>>>> >>>>>> As I understand, a singleton type can only take on a single value. >>>>>> What's the utility in supporting this? >>>>>> >>>>> >>>
