Revision 73b52499688f85aed50b385d9ecc94366a98697b authored by Keno Fischer on 21 September 2018, 19:39:56 UTC, committed by Keno Fischer on 21 September 2018, 19:50:44 UTC
1 parent bd5bb17
ordering.jl
# 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)
const DirectOrdering = Union{ForwardOrdering,ReverseOrdering{ForwardOrdering}}
const Forward = ForwardOrdering()
const Reverse = ReverseOrdering(Forward)
struct By{T} <: Ordering
by::T
end
struct Lt{T} <: Ordering
lt::T
end
struct Perm{O<:Ordering,V<:AbstractVector} <: Ordering
order::O
data::V
end
lt(o::ForwardOrdering, a, b) = isless(a,b)
lt(o::ReverseOrdering, a, b) = lt(o.fwd,b,a)
lt(o::By, a, b) = isless(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
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)
_ord(lt::typeof(isless), by::typeof(identity), order::Ordering) = order
_ord(lt::typeof(isless), by, order::Ordering) = By(by)
_ord(lt, by::typeof(identity), order::Ordering) = Lt(lt)
_ord(lt, by, order::Ordering) = Lt((x,y)->lt(by(x),by(y)))
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
end
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