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@andyferris
Created October 21, 2016 01:44
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Using a `?` as a nullable typename
module Maybe
export ?
immutable ?{T}
hasvalue::Bool
value::T
?() = new(false)
?(x::T) = new(true, x)
end
?{T}(x::T) = ?{T}(x)
?{T}(::Type{T}) = ?{T}()
Base.:*(::Type{?}, x) = ?(x) # I'm confused... ? is a unary in the Scheme file
function Base.show{T}(io::IO, x::?{T})
if x.hasvalue
print(io, x.value)
else
print(io, "?(", T, ")")
end
end
end # module
@andyferris
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On this note we have ?, !, ¿ and ¡ (spanish style inverted question/exclamation marks). And unicode defines a reverse question mark which wikipedia describes as the irony mark. Between these you could develop a whole language for get, isnull/hasvalue, construction, type names, module names, and so-on.

@nalimilan
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Interesting. Though it would still be good to have a real name for that type, with ? only an alias. Else, searches are going to be hard, and for dispatch x::?{T} looks really weird.

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