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?
>>>>>
>>>>
>>
