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diff.jl
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diff.jl
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###############
# differences #
###############
# NOTE: values encountered during an update that are not wrapped in Diffed are
# assumed to have not changed (i.e. constants)
# NOTE: the requirement is that if a method takes any Diffed arguments, it must
# return a Diffed value.
# a Julia method may take non-diffed arguments (which indicate no change, in
# the update context) and return a non-diffed arguments. this means that
# constant expressions (and expressions that depend only on contsant
# expressions) can use code that is not overloaded for Diff types.
# Q: what about regular functions that operate on Diffed values. for example,
# suppose there was a method isdiffed(diff::Diffed) that returned true or
# false. can this function not be used in the model?
# A: a different Julia type (e.g. DiffedValue) would need to be used to
# represent Diffed values that do not represent the semantics of Diff. then
# different Julia methods would be implemented that take in Diffed and
# DiffedValues.
# a value with type Diffed should never appear outside of the update context.
"""
abstract type Diff end
Abstract type for information about a change to a value.
"""
abstract type Diff end
"""
UnknownChange
No information is provided about the change to the value.
"""
struct UnknownChange <: Diff end
"""
NoChange
The value did not change.
"""
struct NoChange <: Diff end
struct SetDiff{V} <: Diff
# elements that were added
added::Set{V}
# elements that were deleted
deleted::Set{V}
end
struct DictDiff{K,V} <: Diff
# keys that that were added and their values
added::AbstractDict{K,V}
# keys that were deleted
deleted::AbstractSet{K}
# map from key to diff value for that key
updated::AbstractDict{K,Diff}
end
struct VectorDiff <: Diff
new_length::Int
prev_length::Int
updated::Dict{Int,Diff}
end
struct IntDiff <: Diff
difference::Int # new - old
end
export Diff
export get_diff, strip_diff
export UnknownChange, NoChange
export SetDiff, DictDiff, VectorDiff
export IntDiff
###############################
## differencing of Julia code #
###############################
"""
Diffed{V,DV <: Diff}
Container for a value and information about a change to its value.
"""
struct Diffed{V,DV <: Diff}
value::V
diff::DV
end
# obtain the diff part of a Diffed value
get_diff(diffed::Diffed) = diffed.diff
# a value that is not wrapped in Diffed is a constant
get_diff(value) = NoChange()
strip_diff(diffed::Diffed) = diffed.value
strip_diff(value) = value
export Diffed, diff, strip_diff
# sets
function Base.in(element::Diffed{V,DV}, set::Diffed{T,DT}) where {V, T <: AbstractSet{V}, DV, DT}
result = strip_diff(element) in strip_diff(set)
Diffed(result, UnknownChange())
end
function Base.in(element::Diffed{V,NoChange}, set::Diffed{T,NoChange}) where {V, T <: AbstractSet{V}}
result = strip_diff(element) in strip_diff(set)
Diffed(result, NoChange())
end
function Base.in(element::Diffed{V,NoChange}, set::Diffed{T, SetDiff{V}}) where {V, T <: AbstractSet{V}}
el = strip_diff(element)
result = el in strip_diff(set)
changed = (el in get_diff(set).added) || (el in get_diff(set).deleted)
if changed
Diffed(result, UnknownChange())
else
Diffed(result, NoChange())
end
end
# TODO handle case where the set is itself a constant but the element is a Diffed
function Base.length(set::Diffed{T,UnknownChange}) where {V, T <: AbstractSet{V}}
result = length(strip_diff(set))
Diffed(result, UnknownChange())
end
function Base.length(set::Diffed{T,NoChange}) where {V, T <: AbstractSet{V}}
result = length(strip_diff(set))
Diffed(result, NoChange())
end
function Base.length(set::Diffed{T,SetDiff{V}}) where {V, T <: AbstractSet{V}}
result = length(strip_diff(set))
n_added = length(get_diff(set).added)
n_deleted = length(get_diff(set).deleted)
if n_added != n_deleted
Diffed(result, IntDiff(n_added - n_deleted))
else
Diffed(result, NoChange())
end
end
# dictionaries
function Base.haskey(dict::Diffed{T,DT}, key::Diffed{K,DK}) where {K, V, T <: AbstractDict{K,V}, DT, DK}
result = haskey(strip_diff(dict), strip_diff(key))
Diffed(result, UnknownChange())
end
function Base.haskey(dict::Diffed{T,NoChange}, key::Union{Diffed{K,NoChange},K}) where {K, V, T <: AbstractDict{K,V}}
result = haskey(strip_diff(dict), strip_diff(key))
Diffed(result, NoChange())
end
function Base.haskey(dict::Diffed{T,DictDiff{K,V}}, key::Union{Diffed{K,NoChange},K}) where {K, V, T <: AbstractDict{K,V}}
result = haskey(strip_diff(dict), key)
changed = (key in get_diff(dict).deleted) || haskey(get_diff(dict).added, key)
if changed
Diffed(result, UnknownChange())
else
Diffed(has, NoChange())
end
end
function Base.getindex(dict::Diffed{T,DT}, key::Diffed{K,DK}) where {K, V, T <: AbstractDict{K,V}, DT, DK}
result = getindex(strip_diff(dict), key)
Diffed(result, UnknownChange())
end
function Base.getindex(dict::Diffed{T,NoChange}, key::Union{Diffed{K,NoChange},K}) where {K, V, T <: AbstractDict{K,V}}
result = getindex(strip_diff(dict), key)
Diffed(result, NoChange())
end
function Base.getindex(dict::Diffed{T,DictDiff{K,V}}, key::Union{Diffed{K,NoChange},K}) where {K, V, T <: AbstractDict{K,V}}
result = getindex(strip_diff(dict), key)
changed = (key in get_diff(dict).deleted) || haskey(get_diff(dict).added, key)
if changed
Diffed(result, UnknownChange())
else
Diffed(val, NoChange())
end
end
# TODO handle case where the dictionary is itself a constant, but the key is a Diffed
# vectors and tuples
function Base.length(vec::Union{Diffed{T,UnknownChange}, Diffed{T,UnknownChange}}) where {T <: Union{AbstractVector,Tuple}}
result = length(strip_diff(vec))
Diffed(result, UnknownChange())
end
function Base.length(vec::Diffed{T,NoChange}) where {T <: Union{AbstractVector,Tuple}}
result = length(strip_diff(vec))
Diffed(result, NoChange())
end
function Base.length(vec::Diffed{T,VectorDiff}) where {T <: Union{AbstractVector,Tuple}}
len = length(strip_diff(vec))
len_diff = get_diff(vec).new_length - get_diff(vec).prev_length
if len_diff == 0
Diffed(len, NoChange())
else
Diffed(len, IntDiff(len_diff))
end
end
# TODO: we know that indeices before teh deleted/inserted idnex have not been changed
function Base.getindex(vec::Union{AbstractVector,Tuple}, idx::Diffed{U,DU}) where {U <: Integer, DU}
result = vec[strip_diff(idx)]
Diffed(result, UnknownChange())
end
function Base.getindex(vec::Union{AbstractVector,Tuple}, idx::Diffed{U,NoChange}) where {U <: Integer}
result = vec[strip_diff(idx)]
Diffed(result, NoChange())
end
function Base.getindex(vec::Diffed{T,DT}, idx::Union{Diffed{U,DU},Integer}) where {T <: Union{AbstractVector,Tuple}, U <: Integer, DT, DU}
result = strip_diff(vec)[strip_diff(idx)]
Diffed(result, UnknownChange())
end
function Base.getindex(vec::Diffed{T,NoChange}, idx::Union{Diffed{U,NoChange},Integer}) where {T <: Union{AbstractVector,Tuple}, U <: Integer}
result = strip_diff(vec)[strip_diff(idx)]
Diffed(result, NoChange())
end
function Base.getindex(vec::Diffed{T,VectorDiff}, idx::Union{Diffed{U,NoChange},Integer}) where {T <: Union{AbstractVector,Tuple}, U <: Integer}
v = strip_diff(vec)
i = strip_diff(idx)
d = get_diff(vec)
result = v[i]
if i > d.prev_length
Diffed(result, UnknownChange())
elseif haskey(d.updated, i)
Diffed(result, d.updated[i])
else
Diffed(result, NoChange())
end
end
# TODO handle case where the vector or tuple is itself a constant, but the index is a Diffed
# built-in mathematical operators and functions
macro diffed_unary_function(fn)
quote
function $(fn)(value::Diffed{T,NoChange}) where {T}
Diffed($(fn)(strip_diff(value)), NoChange())
end
function $(fn)(value::Diffed{T,UnknownChange}) where {T}
Diffed($(fn)(strip_diff(value)), UnknownChange())
end
end
end
macro diffed_binary_function(fn)
quote
function $(fn)(a::Diffed{T,NoChange}, b::Diffed{U,NoChange}) where {T,U}
result = $(fn)(strip_diff(a), strip_diff(b))
Diffed(result, NoChange())
end
function $(fn)(a, b::Diffed{U,NoChange}) where {U}
result = $(fn)(a, strip_diff(b))
Diffed(result, NoChange())
end
function $(fn)(a::Diffed{T,NoChange}, b) where {T}
result = $(fn)(strip_diff(a), b)
Diffed(result, NoChange())
end
function $(fn)(a, b::Diffed{U,DU}) where {U,DU}
result = $(fn)(a, strip_diff(b))
Diffed(result, UnknownChange())
end
function $(fn)(a::Diffed{T,DT}, b) where {T,DT}
result = $(fn)(strip_diff(a), b)
Diffed(result, UnknownChange())
end
function $(fn)(a::Diffed{T,DT}, b::Diffed{U,DU}) where {T,U,DT,DU}
result = $(fn)(strip_diff(a), strip_diff(b))
Diffed(result, UnknownChange())
end
function $(fn)(a::Diffed{T,NoChange}, b::Diffed{U,DU}) where {T,U,DU}
result = $(fn)(strip_diff(a), strip_diff(b))
Diffed(result, UnknownChange())
end
function $(fn)(a::Diffed{T,DT}, b::Diffed{U,NoChange}) where {T,U,DT}
result = $(fn)(strip_diff(a), strip_diff(b))
Diffed(result, UnknownChange())
end
end
end
@diffed_binary_function Base.:+
@diffed_binary_function Base.:*
@diffed_binary_function Base.:-
@diffed_binary_function Base.:/
@diffed_binary_function Base.atan
@diffed_unary_function Base.exp
@diffed_unary_function Base.log
@diffed_unary_function Base.sqrt
@diffed_unary_function Base.sin
@diffed_unary_function Base.cos
@diffed_unary_function Base.tan
# fill
function Base.fill(value::Diffed{V,NoChange}, n::Integer) where {V}
result = fill(strip_diff(value), strip_diff(n))
Diffed(result, NoChange())
end
function Base.fill(value::V, n::Diffed{U,NoChange}) where {V,U <: Integer}
result = fill(value, strip_diff(n))
Diffed(result, NoChange())
end
function Base.fill(value::Diffed{V,NoChange}, n::Diffed{U,NoChange}) where {V,U <: Integer}
result = fill(strip_diff(value), strip_diff(n))
Diffed(result, NoChange())
end
function Base.fill(value::Diffed{V,DV}, n::Diffed{U,NoChange}) where {V,U <: Integer,DV}
result = fill(strip_diff(value), strip_diff(n))
Diffed(result, UnknownChange())
end
function Base.fill(value::Diffed{V,DV}, n::Diffed{U,DU}) where {V,U <: Integer,DU,DV}
result = fill(strip_diff(value), strip_diff(n))
Diffed(result, UnknownChange())
end
# TODO filter, map, reduce, foldl, etc.
# NOTE: just handle the case where the function argument is a constant (a Function not a Diffed{Function,Diff})
# broadcasting (?)
function Base.broadcast(f, a::Diffed{T,NoChange}, b::Diffed{U,NoChange}) where {T,U}
result = broadcast(f, strip_diff(a), strip_diff(b))
Diffed(result, NoChange())
end
function Base.broadcast(f, a::Diffed{T,NoChange}, b) where {T}
result = broadcast(f, strip_diff(a), b)
Diffed(result, NoChange())
end
function Base.broadcast(f, a, b::Diffed{U,NoChange}) where {U}
result = broadcast(f, a, strip_diff(b))
Diffed(result, NoChange())
end
function Base.broadcast(f, a::Diffed{T,DT}, b::Diffed{U,NoChange}) where {T,U,DT}
result = broadcast(f, strip_diff(a), strip_diff(b))
Diffed(result, UnknownChange())
end
function Base.broadcast(f, a::Diffed{T,NoChange}, b::Diffed{U,DU}) where {T,U,DU}
result = broadcast(f, strip_diff(a), strip_diff(b))
Diffed(result, UnknownChange())
end
function Base.broadcast(f, a::Diffed{T,DT}, b::Diffed{U,DU}) where {T,U,DT,DU}
result = broadcast(f, strip_diff(a), strip_diff(b))
Diffed(result, UnknownChange())
end
# control flow
function ifelse(c::Union{Bool,Diffed{Bool,NoChange}}, x::Diffed{T,NoChange}, y::Diffed{U,NoChange}) where {T,U}
result = strip_diff(c) ? strip_diff(x) : strip_diff(y)
Diffed(result, NoChange())
end
function ifelse(c::Diffed{Bool,DC}, x, y) where {DC}
result = strip_diff(c) ? strip_diff(x) : strip_diff(y)
Diffed(result, UnknownChange())
end
function ifelse(c::Bool, x, y)
c ? x : y
end
export ifelse