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# This file is a part of Julia. License is MIT: http://julialang.org/license
immutable NullException <: Exception
end
Nullable{T}(value::T, isnull::Bool=false) = Nullable{T}(value, isnull)
Nullable() = Nullable{Union{}}()
eltype{T}(::Type{Nullable{T}}) = T
convert{T}(::Type{Nullable{T}}, x::Nullable{T}) = x
convert( ::Type{Nullable }, x::Nullable ) = x
function convert{T}(::Type{Nullable{T}}, x::Nullable)
return isnull(x) ? Nullable{T}() : Nullable{T}(convert(T, get(x)))
end
convert{T}(::Type{Nullable{T}}, x::T) = Nullable{T}(x)
convert{T}(::Type{Nullable }, x::T) = Nullable{T}(x)
convert{T}(::Type{Nullable{T}}, ::Void) = Nullable{T}()
convert( ::Type{Nullable }, ::Void) = Nullable{Union{}}()
function show{T}(io::IO, x::Nullable{T})
if x.isnull
print(io, "Nullable{"); show(io, T); print(io, "}()")
else
print(io, "Nullable("); show(io, x.value); print(io, ")")
end
end
get(x::Nullable) = x.isnull ? throw(NullException()) : x.value
@inline function get{T}(x::Nullable{T}, y)
if isbits(T)
ifelse(x.isnull, convert(T, y), x.value)
else
x.isnull ? convert(T, y) : x.value
end
end
isnull(x::Nullable) = x.isnull
function isequal(x::Nullable, y::Nullable)
if x.isnull && y.isnull
return true
elseif x.isnull || y.isnull
return false
else
return isequal(x.value, y.value)
end
end
==(x::Nullable, y::Nullable) = throw(NullException())
const nullablehash_seed = UInt === UInt64 ? 0x932e0143e51d0171 : 0xe51d0171
function hash(x::Nullable, h::UInt)
if x.isnull
return h + nullablehash_seed
else
return hash(x.value, h + nullablehash_seed)
end
end
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