def sketch_update(
lval: syntax.Exp,
old_value: syntax.Exp,
new_value: syntax.Exp,
ctx: [syntax.EVar],
assumptions: [syntax.Exp] = [],
invariants: [syntax.Exp] = []) -> (syntax.Stm, [syntax.Query]):
"""
Write code to update `lval` when it changes from `old_value` to `new_value`.
Variables in `ctx` are assumed to be part of the data structure abstract
state, and `assumptions` will be appended to all generated subgoals.
This function returns a statement (code to update `lval`) and a list of
subgoals (new queries that appear in the code).
"""
if valid(
syntax.EImplies(
syntax.EAll(itertools.chain(assumptions, invariants)),
syntax.EEq(old_value, new_value))):
return (syntax.SNoOp(), [])
subgoals = []
new_value = strip_EStateVar(new_value)
def make_subgoal(e, a=[], docstring=None):
if skip_stateless_synthesis.value and not any(v in ctx
for v in free_vars(e)):
return e
query_name = fresh_name("query")
query = syntax.Query(query_name, syntax.Visibility.Internal, [],
assumptions + a, e, docstring)
query_vars = [v for v in free_vars(query) if v not in ctx]
query.args = [(arg.id, arg.type) for arg in query_vars]
subgoals.append(query)
return syntax.ECall(query_name, tuple(query_vars)).with_type(e.type)
def recurse(*args, **kwargs):
(code, sgs) = sketch_update(*args, **kwargs)
subgoals.extend(sgs)
return code
t = lval.type
if isinstance(t, syntax.TBag) or isinstance(t, syntax.TSet):
to_add = make_subgoal(syntax.EBinOp(new_value, "-",
old_value).with_type(t),
docstring="additions to {}".format(pprint(lval)))
to_del = make_subgoal(
syntax.EBinOp(old_value, "-", new_value).with_type(t),
docstring="deletions from {}".format(pprint(lval)))
v = fresh_var(t.t)
stm = syntax.seq([
syntax.SForEach(v, to_del, syntax.SCall(lval, "remove", [v])),
syntax.SForEach(v, to_add, syntax.SCall(lval, "add", [v]))
])
elif is_numeric(t) and update_numbers_with_deltas.value:
change = make_subgoal(syntax.EBinOp(new_value, "-",
old_value).with_type(t),
docstring="delta for {}".format(pprint(lval)))
stm = syntax.SAssign(lval,
syntax.EBinOp(lval, "+", change).with_type(t))
elif isinstance(t, syntax.TTuple):
get = lambda val, i: syntax.ETupleGet(val, i).with_type(t.ts[i])
stm = syntax.seq([
recurse(get(lval, i),
get(old_value, i),
get(new_value, i),
ctx,
assumptions,
invariants=invariants) for i in range(len(t.ts))
])
elif isinstance(t, syntax.TRecord):
get = lambda val, i: syntax.EGetField(val, t.fields[i][0]).with_type(
t.fields[i][1])
stm = syntax.seq([
recurse(get(lval, i),
get(old_value, i),
get(new_value, i),
ctx,
assumptions,
invariants=invariants) for i in range(len(t.fields))
])
elif isinstance(t, syntax.TMap):
k = fresh_var(lval.type.k)
v = fresh_var(lval.type.v)
key_bag = syntax.TBag(lval.type.k)
old_keys = target_syntax.EMapKeys(old_value).with_type(key_bag)
new_keys = target_syntax.EMapKeys(new_value).with_type(key_bag)
# (1) exit set
deleted_keys = syntax.EBinOp(old_keys, "-",
new_keys).with_type(key_bag)
s1 = syntax.SForEach(
k,
make_subgoal(deleted_keys,
docstring="keys removed from {}".format(
pprint(lval))), target_syntax.SMapDel(lval, k))
# (2) enter/mod set
new_or_modified = target_syntax.EFilter(
new_keys,
syntax.ELambda(
k,
syntax.EAny([
syntax.ENot(syntax.EIn(k, old_keys)),
syntax.ENot(
syntax.EEq(value_at(old_value, k),
value_at(new_value, k)))
]))).with_type(key_bag)
update_value = recurse(v,
value_at(old_value, k),
value_at(new_value, k),
ctx=ctx,
assumptions=assumptions + [
syntax.EIn(k, new_or_modified),
syntax.EEq(v, value_at(old_value, k))
],
invariants=invariants)
s2 = syntax.SForEach(
k,
make_subgoal(new_or_modified,
docstring="new or modified keys from {}".format(
pprint(lval))),
target_syntax.SMapUpdate(lval, k, v, update_value))
stm = syntax.SSeq(s1, s2)
else:
# Fallback rule: just compute a new value from scratch
stm = syntax.SAssign(
lval,
make_subgoal(new_value,
docstring="new value for {}".format(pprint(lval))))
return (stm, subgoals)
def sketch_update(
lval: syntax.Exp,
old_value: syntax.Exp,
new_value: syntax.Exp,
ctx: [syntax.EVar],
assumptions: [syntax.Exp] = []) -> (syntax.Stm, [syntax.Query]):
"""
Write code to update `lval` when it changes from `old_value` to `new_value`.
Variables in `ctx` are assumed to be part of the data structure abstract
state, and `assumptions` will be appended to all generated subgoals.
This function returns a statement (code to update `lval`) and a list of
subgoals (new queries that appear in the code).
"""
if valid(
syntax.EImplies(syntax.EAll(assumptions),
syntax.EEq(old_value, new_value))):
return (syntax.SNoOp(), [])
subgoals = []
def make_subgoal(e, a=[], docstring=None):
e = strip_EStateVar(e)
if skip_stateless_synthesis.value and not any(v in ctx
for v in free_vars(e)):
return e
query_name = fresh_name("query")
query = syntax.Query(query_name, syntax.Visibility.Internal, [],
assumptions + a, e, docstring)
query_vars = [v for v in free_vars(query) if v not in ctx]
query.args = [(arg.id, arg.type) for arg in query_vars]
subgoals.append(query)
return syntax.ECall(query_name, tuple(query_vars)).with_type(e.type)
def recurse(*args, **kwargs):
(code, sgs) = sketch_update(*args, **kwargs)
subgoals.extend(sgs)
return code
t = lval.type
if isinstance(t, syntax.TBag) or isinstance(t, syntax.TSet):
to_add = make_subgoal(syntax.EBinOp(new_value, "-",
old_value).with_type(t),
docstring="additions to {}".format(pprint(lval)))
to_del = make_subgoal(
syntax.EBinOp(old_value, "-", new_value).with_type(t),
docstring="deletions from {}".format(pprint(lval)))
v = fresh_var(t.t)
stm = syntax.seq([
syntax.SForEach(v, to_del, syntax.SCall(lval, "remove", [v])),
syntax.SForEach(v, to_add, syntax.SCall(lval, "add", [v]))
])
# elif isinstance(t, syntax.TList):
# raise NotImplementedError()
elif is_numeric(t):
change = make_subgoal(syntax.EBinOp(new_value, "-",
old_value).with_type(t),
docstring="delta for {}".format(pprint(lval)))
stm = syntax.SAssign(lval,
syntax.EBinOp(lval, "+", change).with_type(t))
elif isinstance(t, syntax.TTuple):
get = lambda val, i: syntax.ETupleGet(val, i).with_type(t.ts[i])
stm = syntax.seq([
recurse(get(lval, i), get(old_value, i), get(new_value, i), ctx,
assumptions) for i in range(len(t.ts))
])
elif isinstance(t, syntax.TRecord):
get = lambda val, i: syntax.EGetField(val, t.fields[i][0]).with_type(
t.fields[i][1])
stm = syntax.seq([
recurse(get(lval, i), get(old_value, i), get(new_value, i), ctx,
assumptions) for i in range(len(t.fields))
])
elif isinstance(t, syntax.THandle):
# handles are tricky, and are dealt with at a higher level
stm = syntax.SNoOp()
elif isinstance(t, syntax.TMap):
value_at = lambda m, k: target_syntax.EMapGet(m, k).with_type(lval.type
.v)
k = fresh_var(lval.type.k)
v = fresh_var(lval.type.v)
key_bag = syntax.TBag(lval.type.k)
if True:
old_keys = target_syntax.EMapKeys(old_value).with_type(key_bag)
new_keys = target_syntax.EMapKeys(new_value).with_type(key_bag)
# (1) exit set
deleted_keys = target_syntax.EFilter(
old_keys,
target_syntax.ELambda(k, syntax.ENot(syntax.EIn(
k, new_keys)))).with_type(key_bag)
s1 = syntax.SForEach(
k,
make_subgoal(deleted_keys,
docstring="keys removed from {}".format(
pprint(lval))),
target_syntax.SMapDel(lval, k))
# (2) modify set
common_keys = target_syntax.EFilter(
old_keys,
target_syntax.ELambda(k,
syntax.EIn(k,
new_keys))).with_type(key_bag)
update_value = recurse(v,
value_at(old_value, k),
value_at(new_value, k),
ctx=ctx,
assumptions=assumptions + [
syntax.EIn(k, common_keys),
syntax.ENot(
syntax.EEq(value_at(old_value, k),
value_at(new_value, k)))
])
altered_keys = target_syntax.EFilter(
common_keys,
target_syntax.ELambda(
k,
syntax.ENot(
syntax.EEq(value_at(old_value, k),
value_at(new_value,
k))))).with_type(key_bag)
s2 = syntax.SForEach(
k,
make_subgoal(altered_keys,
docstring="altered keys in {}".format(
pprint(lval))),
target_syntax.SMapUpdate(lval, k, v, update_value))
# (3) enter set
fresh_keys = target_syntax.EFilter(
new_keys,
target_syntax.ELambda(k, syntax.ENot(syntax.EIn(
k, old_keys)))).with_type(key_bag)
s3 = syntax.SForEach(
k,
make_subgoal(fresh_keys,
docstring="new keys in {}".format(pprint(lval))),
target_syntax.SMapPut(
lval, k,
make_subgoal(value_at(new_value, k),
a=[syntax.EIn(k, fresh_keys)],
docstring="new value inserted at {}".format(
pprint(target_syntax.EMapGet(lval, k))))))
stm = syntax.seq([s1, s2, s3])
else:
# update_value = code to update for value v at key k (given that k is an altered key)
update_value = recurse(v,
value_at(old_value, k),
value_at(new_value, k),
ctx=ctx,
assumptions=assumptions + [
syntax.ENot(
syntax.EEq(value_at(old_value, k),
value_at(new_value, k)))
])
# altered_keys = [k | k <- distinct(lval.keys() + new_value.keys()), value_at(old_value, k) != value_at(new_value, k))]
altered_keys = make_subgoal(
target_syntax.EFilter(
syntax.EUnaryOp(
syntax.UOp.Distinct,
syntax.EBinOp(
target_syntax.EMapKeys(old_value).with_type(
key_bag), "+",
target_syntax.EMapKeys(new_value).with_type(
key_bag)).with_type(key_bag)).with_type(
key_bag),
target_syntax.ELambda(
k,
syntax.ENot(
syntax.EEq(value_at(old_value, k),
value_at(new_value,
k))))).with_type(key_bag))
stm = syntax.SForEach(
k, altered_keys,
target_syntax.SMapUpdate(lval, k, v, update_value))
else:
# Fallback rule: just compute a new value from scratch
stm = syntax.SAssign(
lval,
make_subgoal(new_value,
docstring="new value for {}".format(pprint(lval))))
return (stm, subgoals)