* changed queue to set in AC3

Changed queue to set in AC3 (as in the pseudocode of the original algorithm) to reduce the number of consistency-check due to the redundancy of the same arcs in queue. For example, on the harder1 configuration of the Sudoku CSP the number consistency-check has been reduced from 40464 to 12562!

* re-added test commented by mistake

* added the mentioned AC4 algorithm for constraint propagation

AC3 algorithm has non-optimal worst case time-complexity O(cd^3 ), while AC4 algorithm runs in O(cd^2) worst case time

* added doctest in Sudoku for AC4 and and the possibility of choosing the constant propagation algorithm in mac inference

* removed useless doctest for AC4 in Sudoku because AC4's tests are already present in test_csp.py

* added map coloring SAT problems

* fixed typo errors and removed unnecessary brackets

* reformulated the map coloring problem

* Revert "reformulated the map coloring problem"

This reverts commit 20ab0e5afa238a0556e68f173b07ad32d0779d3b.

* Revert "fixed typo errors and removed unnecessary brackets"

This reverts commit f743146c43b28e0525b0f0b332faebc78c15946f.

* Revert "added map coloring SAT problems"

This reverts commit 9e0fa550e85081cf5b92fb6a3418384ab5a9fdfd.

* Revert "removed useless doctest for AC4 in Sudoku because AC4's tests are already present in test_csp.py"

This reverts commit b3cd24c511a82275f5b43c9f176396e6ba05f67e.

* Revert "added doctest in Sudoku for AC4 and and the possibility of choosing the constant propagation algorithm in mac inference"

This reverts commit 6986247481a05f1e558b93b2bf3cdae395f9c4ee.

* Revert "added the mentioned AC4 algorithm for constraint propagation"

This reverts commit 03551fbf2aa3980b915d4b6fefcbc70f24547b03.

* added map coloring SAT problem

* fixed build error

* Revert "added map coloring SAT problem"

This reverts commit 93af259e4811ddd775429f8a334111b9dd9e268c.

* Revert "fixed build error"

This reverts commit 6641c2c861728f3d43d3931ef201c6f7093cbc96.

* added map coloring SAT problem

* removed redundant parentheses

* added Viterbi algorithm

* added monkey & bananas planning problem

* simplified condition in search.py

* added tests for monkey & bananas planning problem

* removed monkey & bananas planning problem

* Revert "removed monkey & bananas planning problem"

This reverts commit 9d37ae0def15b9e058862cb465da13d2eb926968.

* Revert "added tests for monkey & bananas planning problem"

This reverts commit 24041e9a1a0ab936f7a2608e3662c8efec559382.

* Revert "simplified condition in search.py"

This reverts commit 6d229ce9bde5033802aca29ad3047f37ee6d870d.

* Revert "added monkey & bananas planning problem"

This reverts commit c74933a8905de7bb569bcaed7230930780560874.

* defined the PlanningProblem as a specialization of a search.Problem & fixed typo errors

* fixed doctest in logic.py

* fixed doctest for cascade_distribution

* added ForwardPlanner and tests

* added __lt__ implementation for Expr

* added more tests

* renamed forward planner

* Revert "renamed forward planner"

This reverts commit c4139e50e3a75a036607f4627717d70ad0919554.

* renamed forward planner class & added doc

* added backward planner and tests

* fixed mdp4e.py doctests

* removed ignore_delete_lists_heuristic flag

* fixed heuristic for forward and backward planners

* added SATPlan and tests

* fixed ignore delete lists heuristic in forward and backward planners

* fixed backward planner and added tests

* updated doc

* added nary csp definition and examples

* added CSPlan and tests

* fixed CSPlan

* added book's cryptarithmetic puzzle example

* fixed typo errors in test_csp

* fixed #1111

* added sortedcontainers to yml and doc to CSPlan

* added tests for n-ary csp

* fixed utils.extend

* updated test_probability.py

* converted static methods to functions

* added AC3b and AC4 with heuristic and tests

* added conflict-driven clause learning sat solver

* added tests for cdcl and heuristics

* fixed probability.py

* fixed import

* fixed kakuro

* added Martelli and Montanari rule-based unification algorithm

* removed duplicate standardize_variables

* renamed variables known as built-in functions

* fixed typos in learning.py

* renamed some files and fixed typos

* fixed typos

* fixed typos

* fixed tests

* removed unify_mm

* remove unnecessary brackets

* fixed tests

* moved utility functions to utils.py

* added test case for CYK_parse

* added testcase for CYK_parse

* corrected spacing

* fixed issues like alignment, missing comma etc.

* test case for double tennis problem

* Update planning.py

removed commented print statements.

* test commit

* agents.ipynb

* agents.ipynb

* Fixed all the instances of issue #833

* minor fix and cleared change in agents.ipynb

* Update nlp.py

* add chart parsing test

* add chart parsing section

* add cnf_rules to grammar

* Update nlp.ipynb

* Update test_nlp.py

* add more to CNF section

* Update nlp.py

* add CYK parsing test

* add prob-grammar to notebook

* Update nlp.py

* add weighted choice

* tests for prob grammar + generation

* add test for weighted choice

* Update nlp.py

* Update nlp.py

* Update test_nlp.py

* Add files via upload

* Update nlp.ipynb

* add generate_random

* Update nlp.py

* Update test_nlp.py

* Update nlp.ipynb

* Fix flake8 warnings

* Remove unnecessary #noqa

* Fix doctest

* Modified relevant_pages()

* Additional tests for relevant_pages()

* Add test for determineInlinks()

* Add test for HITS()

* fixed premature updation

* Refactor code to match pseudocode

* Fixed normalize()

* Update test for normalize()

* Exclude test files from flake8 check

* Fix flake8 for main files

* Add flake8 check to build

* Modern string formatting in csp.py.

* Modern string formatting in games.py.

* Modern string formatting in learning.py.

* Modern string formatting in nlp.py.

* Modern string formatting in probability.py.

* Modern string formatting in search.py.

* Replaced {0\!r} by {} if %s.

* Corrected a typo.

* Update search.py

Commenting issues fixed (spacing and punctuation was off sometimes).

* Update agents.py

* Update canvas.py

Grammar

* Update grid.py

* Update learning.py

Added period

* Update logic.py

Fix quoting

* Update mdp.py

Fixed quoting

* Update nlp.py

Capitalization and punctuation fixes

* Update planning.py

* Update probability.py

* Update rl.py

'th' to 'the'

* Update search.py

* Update text.py

* Update utils.py

* Update utils.py

* Update utils.py

* Update learning.py

Typo

* Update utils.py

* Implementing HITS algorithm

* Moving HITS work to nlp.py and test_nlp.py

* modifies Fig. to Figure all over the repository

* fixed a small type in logic.py

* Made Log Usage Consistent in text.py

* Added Explicit Imports from utils

- Fix relative imports in base of is a package or not
- Fix not working notebooks
- Add notebooks to packages sources

Used tool 2to3 to finish the porting to Python 3 plus some fixes by
hand.

These functions, which I had to implement in Python 2.2, are now
available in standard Python.

Fixed error in Chart parses method, where it would
incorrectly return some parses that did not start at the beginning
of the input (and therefore did not span the whole input).