toivoh/freeze.jl

## freeze.jl

# union of immutable types not to freeze/unfreeze
typealias NoFreeze Union(Number, String)

type Frozen{T,COUNT}
    item::T
    watchers::Set{WeakRef}
end

typealias FrozenArray{T,N,COUNT} Frozen{Array{T,N},COUNT}

function show{T,N,COUNT}(fr::FrozenArray{T,N,COUNT})
    print("FrozenArray{$T,$N,count=$COUNT}($(fr.item))")
end
function show{T,COUNT}(fr::Frozen{T,COUNT})
    print("Frozen{$T,fcount=$COUNT}($(fr.item))")
end

Frozen{T}(item::T) = Frozen{T,1}(item, Set{WeakRef}())
function refreeze{T,COUNT}(fr::Frozen{T,COUNT}, delta_count::Int)
    count = COUNT + delta_count
    if (count <= 0); error("can't refreeze with count <= 0"); end
    Frozen{T,count}(fr.item, fr.watchers)
end

freeze(x::NoFreeze) = x
freeze{T}(item::T) = Frozen(item)
freeze(fr::Frozen) = refreeze(fr,+1)

# callback for watchers
notify_unfreeze(::Nothing, ::Frozen) = nothing

unfreeze(x::NoFreeze) = x
function unfreeze{T}(fr::Frozen{T,1})
    for w in fr.watchers
        notify_unfreeze(w, fr)
    end
    fr.item
end
unfreeze(fr::Frozen) = refreeze(fr,-1)

# todo: check against adding/removing twice/keep ref count?
addwatcher(fr::Frozen, watcher) = (add(fr.watchers, WeakRef(watcher)); nothing)
delwatcher(fr::Frozen, watcher) = (del(fr.watchers, WeakRef(watcher)); nothing)

# usage:
# @freeze a b <body>
#
# translates to
#
# begin
#     a = freeze(a); b = freeze(b)
#     ##value = body
#     a = unfreeze(a); b = unfreeze(b)
#     ##value
# end
macro freeze(args...)
    vars = args[1:end-1]
    body = args[end]
    if !allp(v->isa(v, Symbol), vars);
        error("\n@freeze: all but last argument must be symbols")
    end

    pre = {:($var=freeze($var)) | var in vars}
    # todo: check that the vars haven't been changed/save them away
    post = {:($var=unfreeze($var)) | var in vars}
    value = gensym()
    body = :($value=$body)
    expr(:block, pre..., body, post..., value)
end

# todo: define common non-mutating ops to operate on fr.item

	# union of immutable types not to freeze/unfreeze
	typealias NoFreeze Union(Number, String)

	type Frozen{T,COUNT}
	item::T
	watchers::Set{WeakRef}
	end

	typealias FrozenArray{T,N,COUNT} Frozen{Array{T,N},COUNT}

	function show{T,N,COUNT}(fr::FrozenArray{T,N,COUNT})
	print("FrozenArray{$T,$N,count=$COUNT}($(fr.item))")
	end
	function show{T,COUNT}(fr::Frozen{T,COUNT})
	print("Frozen{$T,fcount=$COUNT}($(fr.item))")
	end

	Frozen{T}(item::T) = Frozen{T,1}(item, Set{WeakRef}())
	function refreeze{T,COUNT}(fr::Frozen{T,COUNT}, delta_count::Int)
	count = COUNT + delta_count
	if (count <= 0); error("can't refreeze with count <= 0"); end
	Frozen{T,count}(fr.item, fr.watchers)
	end

	freeze(x::NoFreeze) = x
	freeze{T}(item::T) = Frozen(item)
	freeze(fr::Frozen) = refreeze(fr,+1)

	# callback for watchers
	notify_unfreeze(::Nothing, ::Frozen) = nothing

	unfreeze(x::NoFreeze) = x
	function unfreeze{T}(fr::Frozen{T,1})
	for w in fr.watchers
	notify_unfreeze(w, fr)
	end
	fr.item
	end
	unfreeze(fr::Frozen) = refreeze(fr,-1)

	# todo: check against adding/removing twice/keep ref count?
	addwatcher(fr::Frozen, watcher) = (add(fr.watchers, WeakRef(watcher)); nothing)
	delwatcher(fr::Frozen, watcher) = (del(fr.watchers, WeakRef(watcher)); nothing)

	# usage:
	# @freeze a b <body>
	#
	# translates to
	#
	# begin
	# a = freeze(a); b = freeze(b)
	# ##value = body
	# a = unfreeze(a); b = unfreeze(b)
	# ##value
	# end
	macro freeze(args...)
	vars = args[1:end-1]
	body = args[end]
	if !allp(v->isa(v, Symbol), vars);
	error("\n@freeze: all but last argument must be symbols")
	end

	pre = {:($var=freeze($var)) \| var in vars}
	# todo: check that the vars haven't been changed/save them away
	post = {:($var=unfreeze($var)) \| var in vars}
	value = gensym()
	body = :($value=$body)
	expr(:block, pre..., body, post..., value)
	end

	# todo: define common non-mutating ops to operate on fr.item