# -*- coding: utf-8 -*-
"""
**********
Exceptions
**********

Base exceptions and errors for NetworkX.

"""
__author__ = """Aric Hagberg (hagberg@lanl.gov)\nPieter Swart (swart@lanl.gov)\nDan Schult(dschult@colgate.edu)\nLoïc Séguin-C. <loicseguin@gmail.com>"""
#    Copyright (C) 2004-2015 by
#    Aric Hagberg <hagberg@lanl.gov>
#    Dan Schult <dschult@colgate.edu>
#    Pieter Swart <swart@lanl.gov>
#    All rights reserved.
#    BSD license.
#

# Exception handling

# the root of all Exceptions
class NetworkXException(Exception):
    """Base class for exceptions in NetworkX."""

class NetworkXError(NetworkXException):
    """Exception for a serious error in NetworkX"""

class NetworkXPointlessConcept(NetworkXException):
    """Harary, F. and Read, R. "Is the Null Graph a Pointless Concept?"
In Graphs and Combinatorics Conference, George Washington University.
New York: Springer-Verlag, 1973.
"""

class NetworkXAlgorithmError(NetworkXException):
    """Exception for unexpected termination of algorithms."""

class NetworkXUnfeasible(NetworkXAlgorithmError):
    """Exception raised by algorithms trying to solve a problem
    instance that has no feasible solution."""

class NetworkXNoPath(NetworkXUnfeasible):
    """Exception for algorithms that should return a path when running
    on graphs where such a path does not exist."""

class NetworkXNoCycle(NetworkXUnfeasible):
    """Exception for algorithms that should return a cycle when running
    on graphs where such a cycle does not exist."""

class NetworkXUnbounded(NetworkXAlgorithmError):
    """Exception raised by algorithms trying to solve a maximization
    or a minimization problem instance that is unbounded."""

class NetworkXNotImplemented(NetworkXException):
    """Exception raised by algorithms not implemented for a type of graph."""