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""" 

Recursive Species 

""" 

#***************************************************************************** 

# Copyright (C) 2008 Mike Hansen <mhansen@gmail.com>, 

# 

# Distributed under the terms of the GNU General Public License (GPL) 

# 

# This code is distributed in the hope that it will be useful, 

# but WITHOUT ANY WARRANTY; without even the implied warranty of 

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 

# General Public License for more details. 

# 

# The full text of the GPL is available at: 

# 

# http://www.gnu.org/licenses/ 

#***************************************************************************** 

from sage.combinat.species.species import GenericCombinatorialSpecies 

from sage.combinat.species.structure import SpeciesStructureWrapper 

from sage.rings.all import QQ 

 

 

class CombinatorialSpeciesStructure(SpeciesStructureWrapper): 

pass 

 

 

class CombinatorialSpecies(GenericCombinatorialSpecies): 

def __init__(self): 

""" 

EXAMPLES:: 

 

sage: F = CombinatorialSpecies() 

sage: loads(dumps(F)) 

Combinatorial species 

 

:: 

 

sage: X = species.SingletonSpecies() 

sage: E = species.EmptySetSpecies() 

sage: L = CombinatorialSpecies() 

sage: L.define(E+X*L) 

sage: L.generating_series().coefficients(4) 

[1, 1, 1, 1] 

sage: LL = loads(dumps(L)) 

sage: LL.generating_series().coefficients(4) 

[1, 1, 1, 1] 

""" 

self._generating_series = {} 

self._isotype_generating_series = {} 

self._cycle_index_series = {} 

self._min = None 

self._max = None 

self._weight = 1 

GenericCombinatorialSpecies.__init__(self, min=None, max=None, weight=None) 

 

_default_structure_class = CombinatorialSpeciesStructure 

 

def __hash__(self): 

""" 

EXAMPLES:: 

 

sage: hash(CombinatorialSpecies) #random 

53751280 

 

:: 

 

sage: X = species.SingletonSpecies() 

sage: E = species.EmptySetSpecies() 

sage: L = CombinatorialSpecies() 

sage: L.define(E+X*L) 

sage: hash(L) #random 

-826511807095108317 

""" 

try: 

return hash(('CombinatorialSpecies', id(self._reference))) 

except AttributeError: 

return hash('CombinatorialSpecies') 

 

def __eq__(self, other): 

""" 

TESTS:: 

 

sage: A = species.CombinatorialSpecies() 

sage: B = species.CombinatorialSpecies() 

sage: A == B 

False 

sage: X = species.SingletonSpecies() 

sage: A.define(X+A*A) 

sage: B.define(X+B*B) 

sage: A == B 

True 

 

sage: C = species.CombinatorialSpecies() 

sage: E = species.EmptySetSpecies() 

sage: C.define(E+X*C*C) 

sage: A == C 

False 

""" 

if not isinstance(other, CombinatorialSpecies): 

return False 

if not hasattr(self, "_reference"): 

return False 

if hasattr(self, '_computing_eq'): 

return True 

 

self._computing_eq = True 

res = self._unique_info() == other._unique_info() 

del self._computing_eq 

return res 

 

def __ne__(self, other): 

""" 

Check whether ``self`` is not equal to ``other``. 

 

EXAMPLES:: 

 

sage: A = species.CombinatorialSpecies() 

sage: B = species.CombinatorialSpecies() 

sage: A != B 

True 

sage: X = species.SingletonSpecies() 

sage: A.define(X+A*A) 

sage: B.define(X+B*B) 

sage: A != B 

False 

 

sage: C = species.CombinatorialSpecies() 

sage: E = species.EmptySetSpecies() 

sage: C.define(E+X*C*C) 

sage: A != C 

True 

""" 

return not (self == other) 

 

def _unique_info(self): 

""" 

Return a tuple which should uniquely identify the species. 

 

EXAMPLES:: 

 

sage: F = CombinatorialSpecies() 

sage: F._unique_info() 

(<class 'sage.combinat.species.recursive_species.CombinatorialSpecies'>,) 

 

:: 

 

sage: X = species.SingletonSpecies() 

sage: E = species.EmptySetSpecies() 

sage: L = CombinatorialSpecies() 

sage: L.define(E+X*L) 

sage: L._unique_info() 

(<class 'sage.combinat.species.recursive_species.CombinatorialSpecies'>, 

<class 'sage.combinat.species.sum_species.SumSpecies'>, 

None, 

None, 

1, 

Empty set species, 

Product of (Singleton species) and (Combinatorial species)) 

""" 

if hasattr(self, "_reference"): 

return (self.__class__,) + self._reference._unique_info() 

else: 

return (self.__class__,) 

 

def __getstate__(self): 

""" 

EXAMPLES:: 

 

sage: X = species.SingletonSpecies() 

sage: E = species.EmptySetSpecies() 

sage: L = CombinatorialSpecies() 

sage: L.define(E+X*L) 

sage: L.__getstate__() 

{'reference': Sum of (Empty set species) and (Product of (Singleton species) and (Combinatorial species))} 

""" 

state = {} 

if hasattr(self, '_reference'): 

state['reference'] = self._reference 

return state 

 

def __setstate__(self, state): 

""" 

EXAMPLES:: 

 

sage: X = species.SingletonSpecies() 

sage: E = species.EmptySetSpecies() 

sage: L = CombinatorialSpecies() 

sage: L.define(E+X*L) 

sage: state = L.__getstate__(); state 

{'reference': Sum of (Empty set species) and (Product of (Singleton species) and (Combinatorial species))} 

sage: L._reference = None 

sage: L.__setstate__(state) 

sage: L._reference 

Sum of (Empty set species) and (Product of (Singleton species) and (Combinatorial species)) 

""" 

CombinatorialSpecies.__init__(self) 

if 'reference' in state: 

self.define(state['reference']) 

 

def _structures(self, structure_class, labels): 

""" 

EXAMPLES:: 

 

sage: F = CombinatorialSpecies() 

sage: list(F._structures(F._default_structure_class, [1,2,3])) 

Traceback (most recent call last): 

... 

NotImplementedError 

""" 

if not hasattr(self, "_reference"): 

raise NotImplementedError 

for s in self._reference.structures(labels): 

yield structure_class(self, s) 

 

def _isotypes(self, structure_class, labels): 

""" 

EXAMPLES:: 

 

sage: F = CombinatorialSpecies() 

sage: list(F._isotypes(F._default_structure_class, [1,2,3])) 

Traceback (most recent call last): 

... 

NotImplementedError 

""" 

if not hasattr(self, "_reference"): 

raise NotImplementedError 

for s in self._reference.isotypes(labels): 

yield structure_class(self, s) 

 

def _gs(self, series_ring, base_ring): 

""" 

EXAMPLES:: 

 

sage: F = CombinatorialSpecies() 

sage: F.generating_series() 

Uninitialized lazy power series 

""" 

if base_ring not in self._generating_series: 

self._generating_series[base_ring] = series_ring() 

 

res = self._generating_series[base_ring] 

if hasattr(self, "_reference") and not hasattr(res, "_reference"): 

res._reference = None 

res.define(self._reference.generating_series(base_ring)) 

return res 

 

def _itgs(self, series_ring, base_ring): 

""" 

EXAMPLES:: 

 

sage: F = CombinatorialSpecies() 

sage: F.isotype_generating_series() 

Uninitialized lazy power series 

""" 

if base_ring not in self._isotype_generating_series: 

self._isotype_generating_series[base_ring] = series_ring() 

 

res = self._isotype_generating_series[base_ring] 

if hasattr(self, "_reference") and not hasattr(res, "_reference"): 

res._reference = None 

res.define(self._reference.isotype_generating_series(base_ring)) 

return res 

 

def _cis(self, series_ring, base_ring): 

""" 

EXAMPLES:: 

 

sage: F = CombinatorialSpecies() 

sage: F.cycle_index_series() 

Uninitialized lazy power series 

""" 

if base_ring not in self._cycle_index_series: 

self._cycle_index_series[base_ring] = series_ring() 

 

res = self._cycle_index_series[base_ring] 

if hasattr(self, "_reference") and not hasattr(res, "_reference"): 

res._reference = None 

res.define(self._reference.cycle_index_series(base_ring)) 

return res 

 

def weight_ring(self): 

""" 

EXAMPLES:: 

 

sage: F = species.CombinatorialSpecies() 

sage: F.weight_ring() 

Rational Field 

 

:: 

 

sage: X = species.SingletonSpecies() 

sage: E = species.EmptySetSpecies() 

sage: L = CombinatorialSpecies() 

sage: L.define(E+X*L) 

sage: L.weight_ring() 

Rational Field 

""" 

if not hasattr(self, "_reference"): 

return QQ 

 

if hasattr(self, "_weight_ring_been_called"): 

return QQ 

else: 

self._weight_ring_been_called = True 

res = self._reference.weight_ring() 

del self._weight_ring_been_called 

return res 

 

def define(self, x): 

""" 

Define ``self`` to be equal to the combinatorial species ``x``. 

 

This is 

used to define combinatorial species recursively. All of the real 

work is done by calling the .set() method for each of the series 

associated to self. 

 

EXAMPLES: The species of linear orders L can be recursively defined 

by `L = 1 + X*L` where 1 represents the empty set species 

and X represents the singleton species. 

 

:: 

 

sage: X = species.SingletonSpecies() 

sage: E = species.EmptySetSpecies() 

sage: L = CombinatorialSpecies() 

sage: L.define(E+X*L) 

sage: L.generating_series().coefficients(4) 

[1, 1, 1, 1] 

sage: L.structures([1,2,3]).cardinality() 

6 

sage: L.structures([1,2,3]).list() 

[1*(2*(3*{})), 

1*(3*(2*{})), 

2*(1*(3*{})), 

2*(3*(1*{})), 

3*(1*(2*{})), 

3*(2*(1*{}))] 

 

:: 

 

sage: L = species.LinearOrderSpecies() 

sage: L.generating_series().coefficients(4) 

[1, 1, 1, 1] 

sage: L.structures([1,2,3]).cardinality() 

6 

sage: L.structures([1,2,3]).list() 

[[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]] 

 

TESTS:: 

 

sage: A = CombinatorialSpecies() 

sage: A.define(E+X*A*A) 

sage: A.generating_series().coefficients(6) 

[1, 1, 2, 5, 14, 42] 

sage: A.generating_series().counts(6) 

[1, 1, 4, 30, 336, 5040] 

sage: len(A.structures([1,2,3,4]).list()) 

336 

sage: A.isotype_generating_series().coefficients(6) 

[1, 1, 2, 5, 14, 42] 

sage: len(A.isotypes([1,2,3,4]).list()) 

14 

 

:: 

 

sage: A = CombinatorialSpecies() 

sage: A.define(X+A*A) 

sage: A.generating_series().coefficients(6) 

[0, 1, 1, 2, 5, 14] 

sage: A.generating_series().counts(6) 

[0, 1, 2, 12, 120, 1680] 

sage: len(A.structures([1,2,3]).list()) 

12 

sage: A.isotype_generating_series().coefficients(6) 

[0, 1, 1, 2, 5, 14] 

sage: len(A.isotypes([1,2,3,4]).list()) 

5 

 

:: 

 

sage: X2 = X*X 

sage: X5 = X2*X2*X 

sage: A = CombinatorialSpecies() 

sage: B = CombinatorialSpecies() 

sage: C = CombinatorialSpecies() 

sage: A.define(X5+B*B) 

sage: B.define(X5+C*C) 

sage: C.define(X2+C*C+A*A) 

sage: A.generating_series().coefficients(Integer(10)) 

[0, 0, 0, 0, 0, 1, 0, 0, 1, 2] 

sage: A.generating_series().coefficients(15) 

[0, 0, 0, 0, 0, 1, 0, 0, 1, 2, 5, 4, 14, 10, 48] 

sage: B.generating_series().coefficients(15) 

[0, 0, 0, 0, 1, 1, 2, 0, 5, 0, 14, 0, 44, 0, 138] 

sage: C.generating_series().coefficients(15) 

[0, 0, 1, 0, 1, 0, 2, 0, 5, 0, 15, 0, 44, 2, 142] 

 

:: 

 

sage: F = CombinatorialSpecies() 

sage: F.define(E+X+(X*F+X*X*F)) 

sage: F.generating_series().counts(10) 

[1, 2, 6, 30, 192, 1560, 15120, 171360, 2217600, 32296320] 

sage: F.generating_series().coefficients(10) 

[1, 2, 3, 5, 8, 13, 21, 34, 55, 89] 

sage: F.isotype_generating_series().coefficients(10) 

[1, 2, 3, 5, 8, 13, 21, 34, 55, 89] 

""" 

if not isinstance(x, GenericCombinatorialSpecies): 

raise TypeError("x must be a combinatorial species") 

 

if self.__class__ is not CombinatorialSpecies: 

raise TypeError("only undefined combinatorial species can be set") 

 

self._reference = x 

 

 

def _add_to_digraph(self, d): 

""" 

Adds this species as a vertex to the digraph d along with any 

'children' of this species. 

 

Note that to avoid infinite recursion, we just return if this 

species already occurs in the digraph d. 

 

EXAMPLES:: 

 

sage: d = DiGraph(multiedges=True) 

sage: X = species.SingletonSpecies() 

sage: B = species.CombinatorialSpecies() 

sage: B.define(X+B*B) 

sage: B._add_to_digraph(d); d 

Multi-digraph on 4 vertices 

 

TESTS:: 

 

sage: C = species.CombinatorialSpecies() 

sage: C._add_to_digraph(d) 

Traceback (most recent call last): 

... 

NotImplementedError 

""" 

if self in d: 

return 

try: 

d.add_edge(self, self._reference) 

self._reference._add_to_digraph(d) 

except AttributeError: 

raise NotImplementedError 

 

def _equation(self, var_mapping): 

""" 

Returns the right hand side of an algebraic equation satisfied by 

this species. This is a utility function called by the 

algebraic_equation_system method. 

 

EXAMPLES:: 

 

sage: C = species.CombinatorialSpecies() 

sage: C.algebraic_equation_system() 

Traceback (most recent call last): 

... 

NotImplementedError 

 

:: 

 

sage: B = species.BinaryTreeSpecies() 

sage: B.algebraic_equation_system() 

[-node3^2 + node1, -node1 + node3 - z] 

""" 

try: 

return var_mapping[self._reference] 

except AttributeError: 

raise NotImplementedError