# @generated
# Copyright 2017 The Bazel Authors. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Skylib module containing common set algorithms.
CAUTION: Operating on sets, particularly sets contained in providers, may
asymptotically slow down the analysis phase. While constructing large sets with
addition/union is fast (there is no linear-time copy involved), the
`difference` function and various comparison predicates involve linear-time
traversals.
For convenience, the functions in this module can take either sets or lists as
inputs; operations that take lists treat them as if they were sets (i.e.,
duplicate elements are ignored). Functions that return new sets always return
them as the `set` type, regardless of the types of the inputs.
"""
def _precondition_only_sets_or_lists(*args):
"""Verifies that all arguments are either sets or lists.
The build will fail if any of the arguments is neither a set nor a list.
Args:
*args: A list of values that must be sets or lists.
"""
for a in args:
t = type(a)
if t not in("depset", "list"):
fail("Expected arguments to be depset or list, but found type %s: %r" %
(t, a))
def _is_equal(a, b):
"""Returns whether two sets are equal.
Args:
a: A depset or a list.
b: A depset or a list.
Returns:
True if `a` is equal to `b`, False otherwise.
"""
_precondition_only_sets_or_lists(a, b)
return sorted(depset(a)) == sorted(depset(b))
def _is_subset(a, b):
"""Returns whether `a` is a subset of `b`.
Args:
a: A depset or a list.
b: A depset or a list.
Returns:
True if `a` is a subset of `b`, False otherwise.
"""
_precondition_only_sets_or_lists(a, b)
for e in a:
if e not in b:
return False
return True
def _disjoint(a, b):
"""Returns whether two sets are disjoint.
Two sets are disjoint if they have no elements in common.
Args:
a: A set or list.
b: A set or list.
Returns:
True if `a` and `b` are disjoint, False otherwise.
"""
_precondition_only_sets_or_lists(a, b)
for e in a:
if e in b:
return False
return True
def _intersection(a, b):
"""Returns the intersection of two sets.
Args:
a: A set or list.
b: A set or list.
Returns:
A set containing the elements that are in both `a` and `b`.
"""
_precondition_only_sets_or_lists(a, b)
return depset([e for e in a if e in b])
def _union(*args):
"""Returns the union of several sets.
Args:
*args: An arbitrary number of sets or lists.
Returns:
The set union of all sets or lists in `*args`.
"""
_precondition_only_sets_or_lists(*args)
r = depset()
for a in args:
r += a
return r
def _difference(a, b):
"""Returns the elements in `a` that are not in `b`.
Args:
a: A set or list.
b: A set or list.
Returns:
A set containing the elements that are in `a` but not in `b`.
"""
_precondition_only_sets_or_lists(a, b)
return depset([e for e in a if e not in b])
sets = struct(
difference = _difference,
disjoint = _disjoint,
intersection = _intersection,
is_equal = _is_equal,
is_subset = _is_subset,
union = _union,
)