class CollectionExpression(AbstractExpression):
"""
Base class to provide common code for abstract expressions working on
collections.
"""
_counter = count()
class ConstructCommonResult:
"""
Holder for the result of the "construct_common" method.
"""
def __init__(self, collection_expr, element_vars, index_var,
inner_expr, inner_scope):
self.collection_expr = collection_expr
"""
Resolved expression corresponding to the collection on which the
iteration is done.
:type: ResolvedExpression
"""
self.element_vars = element_vars
"""
List of "element" iteration variables, and their initialization
expression, if any.
we need a list of "element" iteration variables for code generation
purposes. For instance, assuming we iterate on an entity that is an
AST list, we need 3 variables::
* one that contains the node whose type is the root one (AST
lists contain only root nodes in the generated code);
* one that contains the node that is casted to the proper type;
* one that wraps this casted node as an entity.
The first variable is the one used to expand iteration expressions
(see the "user_element_var" property. This is the one that must
have a source name. The other ones are mere code generation
temporaries.
The last variable is the one that is used as the actual iteration
variable in the generated code. This is the only one that will not
require explicit initialization.
:type: list[(ResolvedExpression, ResolvedExpression|None)]
"""
self.index_var = index_var
"""
The index variable as a resolved expression, if required.
:type: ResolvedExpression|None
"""
self.inner_expr = inner_expr
"""
Resolved expression to be evaluated for each collection item.
:type: ResolvedExpression
"""
self.inner_scope = inner_scope
"""
Local variable scope for the body of the iteration.
:type: langkit.expressions.base.LocalVars.Scope
"""
def __init__(self, collection, expr):
"""
:param AbstractExpression collection: Collection on which this map
operation works.
:param expr: Function that takes the induction variable and returns an
expression to evaluate for each item in "collection". If the
function takes two parameters, the first one will also be the
an induction variable for the iteration index.
:type collection: AbstractExpression
"""
super().__init__()
self.collection = collection
self.expr_fn = expr
self.expr = None
self.element_var = None
self.requires_index = False
self.index_var = None
def initialize(self,
expr: AbstractExpression,
element_var: AbstractVariable,
index_var: Optional[AbstractVariable] = None) -> None:
"""
Initialize this expression using already expanded sub-expressions.
This is useful when building expressions with item sub-expressions
outside of our Python DSL.
"""
self.expr = expr
self.element_var = element_var
self.requires_index = index_var is not None
self.index_var = index_var
def do_prepare(self):
# When this expression does not come from our Python DSL (see the
# initialize method above), the sub-expression is ready to use: do not
# try to expand the function.
if self.expr is not None:
return
argspec = inspect.getargspec(self.expr_fn)
check_multiple([
(len(argspec.args)
in (1, 2), 'Invalid collection iteration lambda: only one '
'or two parameters expected'),
(not argspec.varargs and not argspec.keywords,
'Invalid collection iteration lambda: no *args or **kwargs'),
(not argspec.defaults,
'Invalid collection iteration lambda: No default values allowed '
'for arguments')
])
if len(argspec.args) == 2:
self.requires_index = True
index_var_pos = 0
item_var_pos = 1
else:
self.requires_index = False
index_var_pos = None
item_var_pos = 0
# Get the name of the loop variable from the DSL. But don't when we
# have a "default" one, such as for using the ".filter" combinator. In
# this case, it's up to ".filter"'s special implementation to get the
# name from the filter function.
source_name = (None if self.expr_fn == collection_expr_identity else
names.Name.from_lower(argspec.args[item_var_pos]))
self.element_var = AbstractVariable(names.Name("Item_{}".format(
next(CollectionExpression._counter))),
source_name=source_name)
if self.requires_index:
self.index_var = AbstractVariable(
names.Name('I'),
type=T.Int,
source_name=names.Name.from_lower(argspec.args[index_var_pos]))
expr = self.expr_fn(self.index_var, self.element_var)
else:
expr = self.expr_fn(self.element_var)
self.expr = unsugar(expr)
def construct_common(self):
"""
Construct and return the expressions commonly needed by collection
expression subclasses.
:rtype: CollectionExpression.ConstructCommonResult
"""
current_scope = PropertyDef.get_scope()
# First, build the collection expression. From the result, we can
# deduce the type of the element variable.
collection_expr = construct(self.collection)
with_entities = collection_expr.type.is_entity_type
if with_entities:
saved_entity_coll_expr, collection_expr, entity_info = (
collection_expr.destructure_entity())
collection_expr = SequenceExpr(saved_entity_coll_expr,
collection_expr)
check_source_language(
collection_expr.type.is_collection,
'Cannot iterate on {}, which is not a collection'.format(
collection_expr.type.dsl_name))
elt_type = collection_expr.type.element_type
if with_entities:
elt_type = elt_type.entity
self.element_var.set_type(elt_type)
# List of "element" iteration variables
elt_vars = [construct(self.element_var)]
# List of initializing expressions for them
elt_var_inits = []
if with_entities:
entity_var = elt_vars[-1]
node_var = AbstractVariable(names.Name('Bare') +
self.element_var._name,
type=elt_type.element_type)
elt_var_inits.append(
make_as_entity(construct(node_var), entity_info=entity_info))
elt_vars.append(construct(node_var))
# If we are iterating over an AST list, then we get root grammar typed
# values. We need to convert them to the more specific type to get the
# rest of the expression machinery work.
if collection_expr.type.is_list_type:
typed_elt_var = elt_vars[-1]
untyped_elt_var = AbstractVariable(
names.Name('Untyped') + self.element_var._name,
type=get_context().root_grammar_class)
# Initialize the former last variable with a cast from the new last
# variable and push the new last variable.
elt_var_inits.append(
UncheckedCastExpr(construct(untyped_elt_var),
typed_elt_var.type))
elt_vars.append(construct(untyped_elt_var))
# Only then we can build the inner expression
with current_scope.new_child() as inner_scope:
inner_expr = construct(self.expr)
if with_entities:
entity_var.abstract_var.create_local_variable(inner_scope)
if collection_expr.type.is_list_type:
typed_elt_var.abstract_var.create_local_variable(inner_scope)
if self.index_var:
self.index_var.add_to_scope(inner_scope)
elt_var_inits.append(None)
return self.ConstructCommonResult(
collection_expr, funcy.lzip(elt_vars, elt_var_inits),
construct(self.index_var) if self.index_var else None, inner_expr,
inner_scope)
class CollectionExpression(AbstractExpression):
"""
Base class to provide common code for abstract expressions working on
collections.
"""
_counter = count()
def __init__(self, collection, expr):
"""
:param AbstractExpression collection: Collection on which this map
operation works.
:param expr: Function that takes the induction variable and returns an
expression to evaluate for each item in "collection". If the
function takes two parameters, the first one will also be the
an induction variable for the iteration index.
:type collection: AbstractExpression
"""
super(CollectionExpression, self).__init__()
self.collection = collection
self.expr_fn = expr
self.expr = None
self.list_element_var = None
self.element_var = None
self.requires_index = False
self.index_var = None
def do_prepare(self):
argspec = inspect.getargspec(self.expr_fn)
check_multiple([
(len(argspec.args)
in (1, 2), 'Invalid collection iteration lambda: only one '
'or two parameters expected'),
(not argspec.varargs and not argspec.keywords,
'Invalid collection iteration lambda: no *args or **kwargs'),
(not argspec.defaults,
'Invalid collection iteration lambda: No default values allowed '
'for arguments')
])
self.requires_index = len(argspec.args) == 2
self.element_var = AbstractVariable(
names.Name("Item_{}".format(next(CollectionExpression._counter))),
source_name=names.Name.from_lower(argspec.args[0]))
if self.requires_index:
self.index_var = AbstractVariable(
names.Name('I'),
type=LongType,
create_local=True,
source_name=names.Name.from_lower(argspec.args[1]))
expr = self.expr_fn(self.index_var, self.element_var)
else:
expr = self.expr_fn(self.element_var)
self.expr = unsugar(expr)
def construct_common(self):
"""
Construct the expressions commonly needed by collection expression
subclasses, and return them as a tuple constituted of:
1. The resolved collection expression.
2. The resolved expression function passed to CollectionExpression's
constructor.
3. If the collection is an AST list, the iteration variable, whose type
is the root grammar type. None otherwise.
4. The element variable as a resolved expression. In the case of an AST
list collection, this is just 3. converted to the specific type.
5. The index variable as a resolved expression.
6. The inner scope for the iteration.
:rtype: (ResolvedExpression,
ResolvedExpression,
ResolvedExpression|None,
ResolvedExpression,
ResolvedExpression,
langkit.expressions.base.LocalVars.Scope)
"""
collection_expr = construct(
self.collection, lambda t: t.is_collection(),
'Map cannot iterate on {expr_type}, which is not a collection')
self.element_var.set_type(collection_expr.type.element_type())
current_scope = PropertyDef.get_scope()
# If we are iterating over an AST list, then we get root grammar typed
# values. We need to convert them to the more specific type to get the
# rest of the expression machinery work. For this, create a new
# variable.
if collection_expr.type.is_list_type:
self.list_element_var = AbstractVariable(
names.Name("List_Item_{}".format(
next(CollectionExpression._counter))),
type=get_context().root_grammar_class)
self.element_var.add_to_scope(current_scope)
with current_scope.new_child() as iter_scope:
if self.index_var:
PropertyDef.get_scope().add(self.index_var.local_var)
return (collection_expr, construct(self.expr), (construct(
self.list_element_var) if self.list_element_var else None),
construct(self.element_var),
construct(self.index_var) if self.index_var else None,
iter_scope)
