def _get_connected_components(objects, merged_morphisms):
"""
Given a container of morphisms, returns a list of connected
components formed by these morphisms. A connected component
is represented by a diagram consisting of the corresponding
morphisms.
"""
component_index = {}
for o in objects:
component_index[o] = None
# Get the underlying undirected graph of the diagram.
adjlist = DiagramGrid._get_undirected_graph(objects, merged_morphisms)
def traverse_component(object, current_index):
"""
Does a depth-first search traversal of the component
containing ``object``.
"""
component_index[object] = current_index
for o in adjlist[object]:
if component_index[o] is None:
traverse_component(o, current_index)
# Traverse all components.
current_index = 0
for o in adjlist:
if component_index[o] is None:
traverse_component(o, current_index)
current_index += 1
# List the objects of the components.
component_objects = [[] for i in xrange(current_index)]
for o, idx in component_index.items():
component_objects[idx].append(o)
# Finally, list the morphisms belonging to each component.
#
# Note: If some objects are isolated, they will not get any
# morphisms at this stage, and since the layout algorithm
# relies, we are essentially going to lose this object.
# Therefore, check if there are isolated objects and, for each
# of them, provide the trivial identity morphism. It will get
# discarded later, but the object will be there.
component_morphisms = []
for component in component_objects:
current_morphisms = {}
for m in merged_morphisms:
if (m.domain in component) and (m.codomain in component):
current_morphisms[m] = merged_morphisms[m]
if len(component) == 1:
# Let's add an identity morphism, for the sake of
# surely having morphisms in this component.
current_morphisms[IdentityMorphism(component[0])] = FiniteSet()
component_morphisms.append(Diagram(current_morphisms))
return component_morphisms
def test_categories():
from sympy.categories import (Object, Morphism, IdentityMorphism,
NamedMorphism, CompositeMorphism, Category,
Diagram, DiagramGrid)
A1 = Object("A1")
A2 = Object("A2")
A3 = Object("A3")
f1 = NamedMorphism(A1, A2, "f1")
f2 = NamedMorphism(A2, A3, "f2")
id_A1 = IdentityMorphism(A1)
K1 = Category("K1")
assert latex(A1) == "A_{1}"
assert latex(f1) == "f_{1}:A_{1}\\rightarrow A_{2}"
assert latex(id_A1) == "id:A_{1}\\rightarrow A_{1}"
assert latex(f2 * f1) == "f_{2}\\circ f_{1}:A_{1}\\rightarrow A_{3}"
assert latex(K1) == "\mathbf{K_{1}}"
d = Diagram()
assert latex(d) == "\emptyset"
d = Diagram({f1: "unique", f2: S.EmptySet})
assert latex(d) == "\\begin{Bmatrix}f_{2}\\circ f_{1}:A_{1}" \
"\\rightarrow A_{3} : \\emptyset, & id:A_{1}\\rightarrow " \
"A_{1} : \\emptyset, & id:A_{2}\\rightarrow A_{2} : " \
"\\emptyset, & id:A_{3}\\rightarrow A_{3} : \\emptyset, " \
"& f_{1}:A_{1}\\rightarrow A_{2} : \\left\\{unique\\right\\}, " \
"& f_{2}:A_{2}\\rightarrow A_{3} : \\emptyset\\end{Bmatrix}"
d = Diagram({f1: "unique", f2: S.EmptySet}, {f2 * f1: "unique"})
assert latex(d) == "\\begin{Bmatrix}f_{2}\\circ f_{1}:A_{1}" \
"\\rightarrow A_{3} : \\emptyset, & id:A_{1}\\rightarrow " \
"A_{1} : \\emptyset, & id:A_{2}\\rightarrow A_{2} : " \
"\\emptyset, & id:A_{3}\\rightarrow A_{3} : \\emptyset, " \
"& f_{1}:A_{1}\\rightarrow A_{2} : \\left\\{unique\\right\\}," \
" & f_{2}:A_{2}\\rightarrow A_{3} : \\emptyset\\end{Bmatrix}" \
"\\Longrightarrow \\begin{Bmatrix}f_{2}\\circ f_{1}:A_{1}" \
"\\rightarrow A_{3} : \\left\\{unique\\right\\}\\end{Bmatrix}"
# A linear diagram.
A = Object("A")
B = Object("B")
C = Object("C")
f = NamedMorphism(A, B, "f")
g = NamedMorphism(B, C, "g")
d = Diagram([f, g])
grid = DiagramGrid(d)
assert latex(grid) == "\\begin{array}{cc}\n" \
"A & B \\\\\n"\
" & C \n" \
"\\end{array}\n"
def test_categories():
from sympy.categories import Object, NamedMorphism, IdentityMorphism, Category
A = Object("A")
B = Object("B")
f = NamedMorphism(A, B, "f")
id_A = IdentityMorphism(A)
K = Category("K")
assert str(A) == 'Object("A")'
assert str(f) == 'NamedMorphism(Object("A"), Object("B"), "f")'
assert str(id_A) == 'IdentityMorphism(Object("A"))'
assert str(K) == 'Category("K")'
def test_diagram():
A = Object("A")
B = Object("B")
C = Object("C")
f = NamedMorphism(A, B, "f")
g = NamedMorphism(B, C, "g")
id_A = IdentityMorphism(A)
id_B = IdentityMorphism(B)
empty = EmptySet
# Test the addition of identities.
d1 = Diagram([f])
assert d1.objects == FiniteSet(A, B)
assert d1.hom(A, B) == (FiniteSet(f), empty)
assert d1.hom(A, A) == (FiniteSet(id_A), empty)
assert d1.hom(B, B) == (FiniteSet(id_B), empty)
assert d1 == Diagram([id_A, f])
assert d1 == Diagram([f, f])
# Test the addition of composites.
d2 = Diagram([f, g])
homAC = d2.hom(A, C)[0]
assert d2.objects == FiniteSet(A, B, C)
assert g * f in d2.premises.keys()
assert homAC == FiniteSet(g * f)
# Test equality, inequality and hash.
d11 = Diagram([f])
assert d1 == d11
assert d1 != d2
assert hash(d1) == hash(d11)
d11 = Diagram({f: "unique"})
assert d1 != d11
# Make sure that (re-)adding composites (with new properties)
# works as expected.
d = Diagram([f, g], {g * f: "unique"})
assert d.conclusions == Dict({g * f: FiniteSet("unique")})
# Check the hom-sets when there are premises and conclusions.
assert d.hom(A, C) == (FiniteSet(g * f), FiniteSet(g * f))
d = Diagram([f, g], [g * f])
assert d.hom(A, C) == (FiniteSet(g * f), FiniteSet(g * f))
# Check how the properties of composite morphisms are computed.
d = Diagram({f: ["unique", "isomorphism"], g: "unique"})
assert d.premises[g * f] == FiniteSet("unique")
# Check that conclusion morphisms with new objects are not allowed.
d = Diagram([f], [g])
assert d.conclusions == Dict({})
# Test an empty diagram.
d = Diagram()
assert d.premises == Dict({})
assert d.conclusions == Dict({})
assert d.objects == empty
# Check a SymPy Dict object.
d = Diagram(Dict({f: FiniteSet("unique", "isomorphism"), g: "unique"}))
assert d.premises[g * f] == FiniteSet("unique")
# Check the addition of components of composite morphisms.
d = Diagram([g * f])
assert f in d.premises
assert g in d.premises
# Check subdiagrams.
d = Diagram([f, g], {g * f: "unique"})
d1 = Diagram([f])
assert d.is_subdiagram(d1)
assert not d1.is_subdiagram(d)
d = Diagram([NamedMorphism(B, A, "f'")])
assert not d.is_subdiagram(d1)
assert not d1.is_subdiagram(d)
d1 = Diagram([f, g], {g * f: ["unique", "something"]})
assert not d.is_subdiagram(d1)
assert not d1.is_subdiagram(d)
d = Diagram({f: "blooh"})
d1 = Diagram({f: "bleeh"})
assert not d.is_subdiagram(d1)
assert not d1.is_subdiagram(d)
d = Diagram([f, g], {f: "unique", g * f: "veryunique"})
d1 = d.subdiagram_from_objects(FiniteSet(A, B))
assert d1 == Diagram([f], {f: "unique"})
raises(ValueError,
lambda: d.subdiagram_from_objects(FiniteSet(A, Object("D"))))
raises(ValueError, lambda: Diagram({IdentityMorphism(A): "unique"}))
def test_morphisms():
A = Object("A")
B = Object("B")
C = Object("C")
D = Object("D")
# Test the base morphism.
f = NamedMorphism(A, B, "f")
assert f.domain == A
assert f.codomain == B
assert f == NamedMorphism(A, B, "f")
# Test identities.
id_A = IdentityMorphism(A)
id_B = IdentityMorphism(B)
assert id_A.domain == A
assert id_A.codomain == A
assert id_A == IdentityMorphism(A)
assert id_A != id_B
# Test named morphisms.
g = NamedMorphism(B, C, "g")
assert g.name == "g"
assert g != f
assert g == NamedMorphism(B, C, "g")
assert g != NamedMorphism(B, C, "f")
# Test composite morphisms.
assert f == CompositeMorphism(f)
k = g.compose(f)
assert k.domain == A
assert k.codomain == C
assert k.components == Tuple(f, g)
assert g * f == k
assert CompositeMorphism(f, g) == k
assert CompositeMorphism(g * f) == g * f
# Test the associativity of composition.
h = NamedMorphism(C, D, "h")
p = h * g
u = h * g * f
assert h * k == u
assert p * f == u
assert CompositeMorphism(f, g, h) == u
# Test flattening.
u2 = u.flatten("u")
assert isinstance(u2, NamedMorphism)
assert u2.name == "u"
assert u2.domain == A
assert u2.codomain == D
# Test identities.
assert f * id_A == f
assert id_B * f == f
assert id_A * id_A == id_A
assert CompositeMorphism(id_A) == id_A
# Test bad compositions.
raises(ValueError, lambda: f * g)
raises(TypeError, lambda: f.compose(None))
raises(TypeError, lambda: id_A.compose(None))
raises(TypeError, lambda: f * None)
raises(TypeError, lambda: id_A * None)
raises(TypeError, lambda: CompositeMorphism(f, None, 1))
raises(ValueError, lambda: NamedMorphism(A, B, ""))
raises(NotImplementedError, lambda: Morphism(A, B))
def test_morphisms():
A = Object("A")
B = Object("B")
C = Object("C")
D = Object("D")
# Test the base morphism.
f = NamedMorphism(A, B, "f")
assert f.domain == A
assert f.codomain == B
assert f == NamedMorphism(A, B, "f")
# Test identities.
id_A = IdentityMorphism(A)
id_B = IdentityMorphism(B)
assert id_A.domain == A
assert id_A.codomain == A
assert id_A == IdentityMorphism(A)
assert id_A != id_B
# Test named morphisms.
g = NamedMorphism(B, C, "g")
assert g.name == "g"
assert g != f
assert g == NamedMorphism(B, C, "g")
assert g != NamedMorphism(B, C, "f")
# Test composite morphisms.
assert f == CompositeMorphism(f)
k = g.compose(f)
assert k.domain == A
assert k.codomain == C
assert k.components == Tuple(f, g)
assert g * f == k
assert CompositeMorphism(f, g) == k
assert CompositeMorphism(g * f) == g * f
# Test the associativity of composition.
h = NamedMorphism(C, D, "h")
p = h * g
u = h * g * f
assert h * k == u
assert p * f == u
assert CompositeMorphism(f, g, h) == u
# Test flattening.
u2 = u.flatten("u")
assert isinstance(u2, NamedMorphism)
assert u2.name == "u"
assert u2.domain == A
assert u2.codomain == D
# Test identities.
assert f * id_A == f
assert id_B * f == f
assert id_A * id_A == id_A
assert CompositeMorphism(id_A) == id_A
# Test bad compositions.
raises(ValueError, lambda: f * g)
raises(TypeError, lambda: f.compose(None))
raises(TypeError, lambda: id_A.compose(None))
raises(TypeError, lambda: f * None)
raises(TypeError, lambda: id_A * None)
raises(TypeError, lambda: CompositeMorphism(f, None, 1))
raises(ValueError, lambda: NamedMorphism(A, B, ""))
raises(NotImplementedError, lambda: Morphism(A, B))