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# This file is a part of Julia. License is MIT: https://julialang.org/license
module Order
import ..@__MODULE__, ..parentmodule
const Base = parentmodule(@__MODULE__)
import .Base:
AbstractVector, @propagate_inbounds, isless, identity, getindex,
+, -, !, &, <, |
## notions of element ordering ##
export # not exported by Base
Ordering, Forward, Reverse,
By, Lt, Perm,
ReverseOrdering, ForwardOrdering,
DirectOrdering,
lt, ord, ordtype
abstract type Ordering end
struct ForwardOrdering <: Ordering end
struct ReverseOrdering{Fwd<:Ordering} <: Ordering
fwd::Fwd
end
ReverseOrdering(rev::ReverseOrdering) = rev.fwd
ReverseOrdering(fwd::Fwd) where {Fwd} = ReverseOrdering{Fwd}(fwd)
ReverseOrdering() = ReverseOrdering(ForwardOrdering())
const DirectOrdering = Union{ForwardOrdering,ReverseOrdering{ForwardOrdering}}
const Forward = ForwardOrdering()
const Reverse = ReverseOrdering()
struct By{T, O} <: Ordering
by::T
order::O
end
# backwards compatibility with VERSION < v"1.5-"
By(by) = By(by, Forward)
struct Lt{T} <: Ordering
lt::T
end
struct Perm{O<:Ordering,V<:AbstractVector} <: Ordering
order::O
data::V
end
ReverseOrdering(by::By) = By(by.by, ReverseOrdering(by.order))
ReverseOrdering(perm::Perm) = Perm(ReverseOrdering(perm.order), perm.data)
lt(o::ForwardOrdering, a, b) = isless(a,b)
lt(o::ReverseOrdering, a, b) = lt(o.fwd,b,a)
lt(o::By, a, b) = lt(o.order,o.by(a),o.by(b))
lt(o::Lt, a, b) = o.lt(a,b)
@propagate_inbounds function lt(p::Perm, a::Integer, b::Integer)
da = p.data[a]
db = p.data[b]
lt(p.order, da, db) | (!lt(p.order, db, da) & (a < b))
end
_ord(lt::typeof(isless), by::typeof(identity), order::Ordering) = order
_ord(lt::typeof(isless), by, order::Ordering) = By(by, order)
function _ord(lt, by, order::Ordering)
if order === Forward
return Lt((x, y) -> lt(by(x), by(y)))
elseif order === Reverse
return Lt((x, y) -> lt(by(y), by(x)))
else
error("Passing both lt= and order= arguments is ambiguous; please pass order=Forward or order=Reverse (or leave default)")
end
end
ord(lt, by, rev::Nothing, order::Ordering=Forward) = _ord(lt, by, order)
function ord(lt, by, rev::Bool, order::Ordering=Forward)
o = _ord(lt, by, order)
return rev ? ReverseOrdering(o) : o
end
# This function is not in use anywhere in Base but we observed
# use in sorting-related packages (#34719). It's probably best to move
# this functionality to those packages in the future; let's remind/force
# ourselves to deprecate this in v2.0.
# The following clause means `if VERSION < v"2.0-"` but it also works during
# bootstrap. For the same reason, we need to write `Int32` instead of `Cint`.
if ccall(:jl_ver_major, Int32, ()) < 2
ordtype(o::ReverseOrdering, vs::AbstractArray) = ordtype(o.fwd, vs)
ordtype(o::Perm, vs::AbstractArray) = ordtype(o.order, o.data)
# TODO: here, we really want the return type of o.by, without calling it
ordtype(o::By, vs::AbstractArray) = try typeof(o.by(vs[1])) catch; Any end
ordtype(o::Ordering, vs::AbstractArray) = eltype(vs)
end
end
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