Module grscheller.datastructures.stack
Module grscheller.datastructure.stack - LIFO stack:
Module implementing a LIFO stack using a singularly linked linear tree of nodes. The nodes can be safely shared between different Stack instances and are an implementation detail hidden from client code.
Pushing to, popping from, and getting the length of the stack are all O(1) operations.
Classes
grscheller.datastructure.PStack - LIFO stack, mutable, procedural interface grscheller.datastructure.FStack - LIFO stack, immutable, functional interface
Expand source code
# Copyright 2023 Geoffrey R. Scheller
#
# 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.
"""Module grscheller.datastructure.stack - LIFO stack:
Module implementing a LIFO stack using a singularly linked linear tree of
nodes. The nodes can be safely shared between different Stack instances and
are an implementation detail hidden from client code.
Pushing to, popping from, and getting the length of the stack are all O(1)
operations.
Classes:
grscheller.datastructure.PStack - LIFO stack, mutable, procedural interface
grscheller.datastructure.FStack - LIFO stack, immutable, functional interface
"""
from __future__ import annotations
__all__ = ['PStack', 'FStack']
__author__ = "Geoffrey R. Scheller"
__copyright__ = "Copyright (c) 2023 Geoffrey R. Scheller"
__license__ = "Appache License 2.0"
from typing import Any, Callable, Self
from itertools import chain
from .core.iterlib import merge, exhaust
from .core.carray import CArray
class _Node():
"""Class implementing nodes that can be linked together to form a singularly
linked list. A node always contain data. It either has a reference to the
next _Node object or None to indicate the bottom of the linked list.
Nodes can safely be shared between different Stack instances.
"""
def __init__(self, data: Any, nodeNext: _Node|None):
"""Construct an element of a linked list, semantically immutable.
Note: It is the Stack class's responsibility that the _data property is
never set to None.
"""
self._data = data
self._next = nodeNext
def __bool__(self):
"""Always return true, None will return as false"""
return True
class Stack():
"""Abstract base class for the purposes of DRY inheritance of classes
implementing stack type data structures. Each stack is a very simple
stateful object containing a count of the number of elements on it and
a reference to an immutable node of a linear tree of singularly linked
nodes. Different stack objects can safely share the same data by each
pointing to the same node. Each stack class ensures None values do not
get pushed onto the the stack.
"""
def __init__(self, *ds):
"""Construct a LIFO Stack"""
self._head = None
self._count = 0
for d in ds:
if d is not None:
node = _Node(d, self._head)
self._head = node
self._count += 1
def copy(self) -> Stack:
raise NotImplementedError
def __bool__(self) -> bool:
"""Returns true if stack is not empty"""
return self._count > 0
def __len__(self) -> int:
"""Returns current number of values on the stack"""
return self._count
def __iter__(self):
"""Iterator yielding data stored on the stack, starting at the head"""
node = self._head
while node:
yield node._data
node = node._next
def __reversed__(self):
"""Reverse iterate over the contents of the stack"""
return reversed(CArray(*self))
def __eq__(self, other: Any):
"""Returns True if all the data stored on the two stacks are the same
and the two stacks are of the same subclass. Worst case is O(n) behavior
which happens when all the corresponding data elements on the two stacks
are equal, in whatever sense they equality is defined, and none of the
nodes are shared.
"""
if not isinstance(other, type(self)):
return False
if self._count != other._count:
return False
left = self._head
right = other._head
nn = self._count
while nn > 0:
if left is right:
return True
if left is None or right is None:
return True
if left._data != right._data:
return False
left = left._next
right = right._next
nn -= 1
return True
class PStack(Stack):
"""Class implementing a Last In, First Out (LIFO) stack data structure. The
stack contains a singularly linked list of nodes. Class designed to share
nodes with other PStack instances.
PStacks stacks are stateful objects, values can be pushed on & popped off.
A stack points to either the top node of a singlely linked list, or to
None which indicates an empty stack.
A stack keeps a count of the number of objects currently on it.
None represents the absence of a value and ignored if pushed on a stack.
"""
def __init__(self, *ds):
"""Construct a stateful LIFO Stack"""
super().__init__(*ds)
def __repr__(self):
"""Display the data in the stack, left to right starting at bottom"""
return '|| ' + ' <- '.join(reversed(CArray(*self).map(repr))) + ' ><'
def copy(self) -> PStack:
"""Return shallow copy of a PStack in O(1) time & space complexity"""
pstack = PStack()
pstack._head = self._head
pstack._count = self._count
return pstack
def push(self, *ds: Any) -> Self:
"""Push data that is not NONE onto top of stack,
return the stack being pushed.
"""
for d in ds:
if d is not None:
node = _Node(d, self._head)
self._head = node
self._count += 1
return self
def pop(self) -> Any:
"""Pop data off of top of stack"""
if self._head is None:
return None
else:
data = self._head._data
self._head = self._head._next
self._count -= 1
return data
def peak(self, default: Any=None) -> Any:
"""Returns the data at the top of the stack. Does not consume the data.
If stack is empty, data does not exist so in that case return default.
"""
if self._head is None:
return default
return self._head._data
def map(self, f: Callable[[Any], PStack]) -> None:
"""Maps a function (or callable object) over the values on the stack.
Returns a new stack with new nodes. None values surpressed.
"""
newPStack = PStack(*map(f, reversed(self)))
self._head = newPStack._head
self._count = newPStack._count
def flatMap(self, f: Callable[[Any], PStack]) -> None:
"""Apply function and flatten result, returns new instance.
Merge the stacks produced sequentially front-to-back.
"""
newPStack = PStack(*chain(*map(reversed, map(f, reversed(self)))))
self._head = newPStack._head
self._count = newPStack._count
def mergeMap(self, f: Callable[[Any], PStack]) -> None:
"""Apply function and flatten result, returns new instance.
Round Robin Merge the stacks produced until first cached stack is
exhausted.
"""
newPStack = PStack(*merge(*map(reversed, map(f, reversed(self)))))
self._head = newPStack._head
self._count = newPStack._count
def exhaustMap(self, f: Callable[[Any], PStack]) -> None:
"""Apply function and flatten result, returns new instance
Round Robin Merge the stacks produced until all the cached stacks are
exhausted.
"""
newPStack = PStack(*exhaust(*map(reversed, map(f, reversed(self)))))
self._head = newPStack._head
self._count = newPStack._count
class FStack(Stack):
"""Class implementing an immutable singularly linked stack data
structure consisting of a singularly linked list of nodes. This
class is designed to share nodes with other FStack instances.
FStack stacks are immutable objects.
A functional stack points to either the top node in the list, or to None
which indicates an empty stack.
A functional stack has the count of the number of objects on it.
None represents the absence of a value and ignored if pushed on an FStack.
"""
def __init__(self, *ds):
"""Construct an immutable LIFO Stack"""
super().__init__(*ds)
def __repr__(self):
"""Display the data in the stack, left to right starting at bottom"""
return '| ' + ' <- '.join(reversed(CArray(*self).map(repr))) + ' ><'
def copy(self) -> FStack:
"""Return shallow copy of a FStack in O(1) time & space complexity"""
fstack = FStack()
fstack._head = self._head
fstack._count = self._count
return fstack
def head(self, default: Any=None) -> Any:
"""Returns the data at the top of the stack. Does not consume the data.
If stack is empty, head does not exist so in that case return default.
"""
if self._head is None:
return default
return self._head._data
def tail(self, default=None) -> FStack:
"""Return tail of the stack. If Stack is empty, tail does not exist, so
return a default of type FStack instead. If default is not given, return
an empty FStack.
"""
if self._head:
stack = FStack()
stack._head = self._head._next
stack._count = self._count - 1
return stack
elif default is None:
return FStack()
else:
return default
def cons(self, data: Any) -> FStack:
"""Return a new stack with data as head and self as tail. Constructing
a stack using a non-existent value as head results in a non-existent
stack. In that case, just return a copy of the stack.
"""
if data is not None:
stack = FStack()
stack._head = _Node(data, self._head)
stack._count = self._count + 1
return stack
else:
return self.copy()
def map(self, f: Callable[[Any], FStack]) -> FStack:
"""Maps a function (or callable object) over the values on the stack.
Returns a new stack with new nodes. None values surpressed.
"""
return FStack(*map(f, reversed(self)))
def flatMap(self, f: Callable[[Any], FStack]) -> FStack:
"""Apply function and flatten result, returns new instance
Merge the stacks produced sequentially front-to-back.
"""
return FStack(*chain(*map(reversed, map(f, reversed(self)))))
def mergeMap(self, f: Callable[[Any], FStack]) -> FStack:
"""Apply function and flatten result, returns new instance
Round Robin Merge the stacks produced until first cached stack is
exhausted.
"""
return FStack(*merge(*map(reversed, map(f, reversed(self)))))
def exhaustMap(self, f: Callable[[Any], FStack]) -> FStack:
"""Apply function and flatten result, returns new instance
Round Robin Merge the stacks produced until all the cached stacks are
exhausted.
"""
return FStack(*exhaust(*map(reversed, map(f, reversed(self)))))
if __name__ == "__main__":
pass
Classes
class FStack (*ds)
-
Class implementing an immutable singularly linked stack data structure consisting of a singularly linked list of nodes. This class is designed to share nodes with other FStack instances.
FStack stacks are immutable objects.
A functional stack points to either the top node in the list, or to None which indicates an empty stack.
A functional stack has the count of the number of objects on it.
None represents the absence of a value and ignored if pushed on an FStack.
Construct an immutable LIFO Stack
Expand source code
class FStack(Stack): """Class implementing an immutable singularly linked stack data structure consisting of a singularly linked list of nodes. This class is designed to share nodes with other FStack instances. FStack stacks are immutable objects. A functional stack points to either the top node in the list, or to None which indicates an empty stack. A functional stack has the count of the number of objects on it. None represents the absence of a value and ignored if pushed on an FStack. """ def __init__(self, *ds): """Construct an immutable LIFO Stack""" super().__init__(*ds) def __repr__(self): """Display the data in the stack, left to right starting at bottom""" return '| ' + ' <- '.join(reversed(CArray(*self).map(repr))) + ' ><' def copy(self) -> FStack: """Return shallow copy of a FStack in O(1) time & space complexity""" fstack = FStack() fstack._head = self._head fstack._count = self._count return fstack def head(self, default: Any=None) -> Any: """Returns the data at the top of the stack. Does not consume the data. If stack is empty, head does not exist so in that case return default. """ if self._head is None: return default return self._head._data def tail(self, default=None) -> FStack: """Return tail of the stack. If Stack is empty, tail does not exist, so return a default of type FStack instead. If default is not given, return an empty FStack. """ if self._head: stack = FStack() stack._head = self._head._next stack._count = self._count - 1 return stack elif default is None: return FStack() else: return default def cons(self, data: Any) -> FStack: """Return a new stack with data as head and self as tail. Constructing a stack using a non-existent value as head results in a non-existent stack. In that case, just return a copy of the stack. """ if data is not None: stack = FStack() stack._head = _Node(data, self._head) stack._count = self._count + 1 return stack else: return self.copy() def map(self, f: Callable[[Any], FStack]) -> FStack: """Maps a function (or callable object) over the values on the stack. Returns a new stack with new nodes. None values surpressed. """ return FStack(*map(f, reversed(self))) def flatMap(self, f: Callable[[Any], FStack]) -> FStack: """Apply function and flatten result, returns new instance Merge the stacks produced sequentially front-to-back. """ return FStack(*chain(*map(reversed, map(f, reversed(self))))) def mergeMap(self, f: Callable[[Any], FStack]) -> FStack: """Apply function and flatten result, returns new instance Round Robin Merge the stacks produced until first cached stack is exhausted. """ return FStack(*merge(*map(reversed, map(f, reversed(self))))) def exhaustMap(self, f: Callable[[Any], FStack]) -> FStack: """Apply function and flatten result, returns new instance Round Robin Merge the stacks produced until all the cached stacks are exhausted. """ return FStack(*exhaust(*map(reversed, map(f, reversed(self)))))
Ancestors
- grscheller.datastructures.stack.Stack
Methods
def cons(self, data: Any) ‑> FStack
-
Return a new stack with data as head and self as tail. Constructing a stack using a non-existent value as head results in a non-existent stack. In that case, just return a copy of the stack.
Expand source code
def cons(self, data: Any) -> FStack: """Return a new stack with data as head and self as tail. Constructing a stack using a non-existent value as head results in a non-existent stack. In that case, just return a copy of the stack. """ if data is not None: stack = FStack() stack._head = _Node(data, self._head) stack._count = self._count + 1 return stack else: return self.copy()
def copy(self) ‑> FStack
-
Return shallow copy of a FStack in O(1) time & space complexity
Expand source code
def copy(self) -> FStack: """Return shallow copy of a FStack in O(1) time & space complexity""" fstack = FStack() fstack._head = self._head fstack._count = self._count return fstack
def exhaustMap(self, f: Callable[[Any], FStack]) ‑> FStack
-
Apply function and flatten result, returns new instance
Round Robin Merge the stacks produced until all the cached stacks are exhausted.
Expand source code
def exhaustMap(self, f: Callable[[Any], FStack]) -> FStack: """Apply function and flatten result, returns new instance Round Robin Merge the stacks produced until all the cached stacks are exhausted. """ return FStack(*exhaust(*map(reversed, map(f, reversed(self)))))
def flatMap(self, f: Callable[[Any], FStack]) ‑> FStack
-
Apply function and flatten result, returns new instance
Merge the stacks produced sequentially front-to-back.
Expand source code
def flatMap(self, f: Callable[[Any], FStack]) -> FStack: """Apply function and flatten result, returns new instance Merge the stacks produced sequentially front-to-back. """ return FStack(*chain(*map(reversed, map(f, reversed(self)))))
def head(self, default: Any = None) ‑> Any
-
Returns the data at the top of the stack. Does not consume the data. If stack is empty, head does not exist so in that case return default.
Expand source code
def head(self, default: Any=None) -> Any: """Returns the data at the top of the stack. Does not consume the data. If stack is empty, head does not exist so in that case return default. """ if self._head is None: return default return self._head._data
def map(self, f: Callable[[Any], FStack]) ‑> FStack
-
Maps a function (or callable object) over the values on the stack.
Returns a new stack with new nodes. None values surpressed.
Expand source code
def map(self, f: Callable[[Any], FStack]) -> FStack: """Maps a function (or callable object) over the values on the stack. Returns a new stack with new nodes. None values surpressed. """ return FStack(*map(f, reversed(self)))
def mergeMap(self, f: Callable[[Any], FStack]) ‑> FStack
-
Apply function and flatten result, returns new instance
Round Robin Merge the stacks produced until first cached stack is exhausted.
Expand source code
def mergeMap(self, f: Callable[[Any], FStack]) -> FStack: """Apply function and flatten result, returns new instance Round Robin Merge the stacks produced until first cached stack is exhausted. """ return FStack(*merge(*map(reversed, map(f, reversed(self)))))
def tail(self, default=None) ‑> FStack
-
Return tail of the stack. If Stack is empty, tail does not exist, so return a default of type FStack instead. If default is not given, return an empty FStack.
Expand source code
def tail(self, default=None) -> FStack: """Return tail of the stack. If Stack is empty, tail does not exist, so return a default of type FStack instead. If default is not given, return an empty FStack. """ if self._head: stack = FStack() stack._head = self._head._next stack._count = self._count - 1 return stack elif default is None: return FStack() else: return default
class PStack (*ds)
-
Class implementing a Last In, First Out (LIFO) stack data structure. The stack contains a singularly linked list of nodes. Class designed to share nodes with other PStack instances.
PStacks stacks are stateful objects, values can be pushed on & popped off.
A stack points to either the top node of a singlely linked list, or to None which indicates an empty stack.
A stack keeps a count of the number of objects currently on it.
None represents the absence of a value and ignored if pushed on a stack.
Construct a stateful LIFO Stack
Expand source code
class PStack(Stack): """Class implementing a Last In, First Out (LIFO) stack data structure. The stack contains a singularly linked list of nodes. Class designed to share nodes with other PStack instances. PStacks stacks are stateful objects, values can be pushed on & popped off. A stack points to either the top node of a singlely linked list, or to None which indicates an empty stack. A stack keeps a count of the number of objects currently on it. None represents the absence of a value and ignored if pushed on a stack. """ def __init__(self, *ds): """Construct a stateful LIFO Stack""" super().__init__(*ds) def __repr__(self): """Display the data in the stack, left to right starting at bottom""" return '|| ' + ' <- '.join(reversed(CArray(*self).map(repr))) + ' ><' def copy(self) -> PStack: """Return shallow copy of a PStack in O(1) time & space complexity""" pstack = PStack() pstack._head = self._head pstack._count = self._count return pstack def push(self, *ds: Any) -> Self: """Push data that is not NONE onto top of stack, return the stack being pushed. """ for d in ds: if d is not None: node = _Node(d, self._head) self._head = node self._count += 1 return self def pop(self) -> Any: """Pop data off of top of stack""" if self._head is None: return None else: data = self._head._data self._head = self._head._next self._count -= 1 return data def peak(self, default: Any=None) -> Any: """Returns the data at the top of the stack. Does not consume the data. If stack is empty, data does not exist so in that case return default. """ if self._head is None: return default return self._head._data def map(self, f: Callable[[Any], PStack]) -> None: """Maps a function (or callable object) over the values on the stack. Returns a new stack with new nodes. None values surpressed. """ newPStack = PStack(*map(f, reversed(self))) self._head = newPStack._head self._count = newPStack._count def flatMap(self, f: Callable[[Any], PStack]) -> None: """Apply function and flatten result, returns new instance. Merge the stacks produced sequentially front-to-back. """ newPStack = PStack(*chain(*map(reversed, map(f, reversed(self))))) self._head = newPStack._head self._count = newPStack._count def mergeMap(self, f: Callable[[Any], PStack]) -> None: """Apply function and flatten result, returns new instance. Round Robin Merge the stacks produced until first cached stack is exhausted. """ newPStack = PStack(*merge(*map(reversed, map(f, reversed(self))))) self._head = newPStack._head self._count = newPStack._count def exhaustMap(self, f: Callable[[Any], PStack]) -> None: """Apply function and flatten result, returns new instance Round Robin Merge the stacks produced until all the cached stacks are exhausted. """ newPStack = PStack(*exhaust(*map(reversed, map(f, reversed(self))))) self._head = newPStack._head self._count = newPStack._count
Ancestors
- grscheller.datastructures.stack.Stack
Methods
def copy(self) ‑> PStack
-
Return shallow copy of a PStack in O(1) time & space complexity
Expand source code
def copy(self) -> PStack: """Return shallow copy of a PStack in O(1) time & space complexity""" pstack = PStack() pstack._head = self._head pstack._count = self._count return pstack
def exhaustMap(self, f: Callable[[Any], PStack]) ‑> None
-
Apply function and flatten result, returns new instance
Round Robin Merge the stacks produced until all the cached stacks are exhausted.
Expand source code
def exhaustMap(self, f: Callable[[Any], PStack]) -> None: """Apply function and flatten result, returns new instance Round Robin Merge the stacks produced until all the cached stacks are exhausted. """ newPStack = PStack(*exhaust(*map(reversed, map(f, reversed(self))))) self._head = newPStack._head self._count = newPStack._count
def flatMap(self, f: Callable[[Any], PStack]) ‑> None
-
Apply function and flatten result, returns new instance.
Merge the stacks produced sequentially front-to-back.
Expand source code
def flatMap(self, f: Callable[[Any], PStack]) -> None: """Apply function and flatten result, returns new instance. Merge the stacks produced sequentially front-to-back. """ newPStack = PStack(*chain(*map(reversed, map(f, reversed(self))))) self._head = newPStack._head self._count = newPStack._count
def map(self, f: Callable[[Any], PStack]) ‑> None
-
Maps a function (or callable object) over the values on the stack.
Returns a new stack with new nodes. None values surpressed.
Expand source code
def map(self, f: Callable[[Any], PStack]) -> None: """Maps a function (or callable object) over the values on the stack. Returns a new stack with new nodes. None values surpressed. """ newPStack = PStack(*map(f, reversed(self))) self._head = newPStack._head self._count = newPStack._count
def mergeMap(self, f: Callable[[Any], PStack]) ‑> None
-
Apply function and flatten result, returns new instance.
Round Robin Merge the stacks produced until first cached stack is exhausted.
Expand source code
def mergeMap(self, f: Callable[[Any], PStack]) -> None: """Apply function and flatten result, returns new instance. Round Robin Merge the stacks produced until first cached stack is exhausted. """ newPStack = PStack(*merge(*map(reversed, map(f, reversed(self))))) self._head = newPStack._head self._count = newPStack._count
def peak(self, default: Any = None) ‑> Any
-
Returns the data at the top of the stack. Does not consume the data. If stack is empty, data does not exist so in that case return default.
Expand source code
def peak(self, default: Any=None) -> Any: """Returns the data at the top of the stack. Does not consume the data. If stack is empty, data does not exist so in that case return default. """ if self._head is None: return default return self._head._data
def pop(self) ‑> Any
-
Pop data off of top of stack
Expand source code
def pop(self) -> Any: """Pop data off of top of stack""" if self._head is None: return None else: data = self._head._data self._head = self._head._next self._count -= 1 return data
def push(self, *ds: Any) ‑> Self
-
Push data that is not NONE onto top of stack, return the stack being pushed.
Expand source code
def push(self, *ds: Any) -> Self: """Push data that is not NONE onto top of stack, return the stack being pushed. """ for d in ds: if d is not None: node = _Node(d, self._head) self._head = node self._count += 1 return self