def assume(self):
"""
TEST::
sage: from sage.symbolic.assumptions import GenericDeclaration
sage: decl = GenericDeclaration(x, 'even')
sage: decl.assume()
sage: cos(x*pi).simplify()
1
sage: decl2 = GenericDeclaration(x, 'odd')
sage: decl2.assume()
Traceback (most recent call last):
...
ValueError: Assumption is inconsistent
sage: decl.forget()
"""
from sage.calculus.calculus import maxima
if self._context is None:
# We get the list here because features may be added with time.
valid_features = list(maxima("features"))
if self._assumption not in [repr(x).strip() for x in list(valid_features)]:
raise ValueError, "%s not a valid assumption, must be one of %s" % (self._assumption, valid_features)
cur = maxima.get("context")
self._context = maxima.newcontext('context' + maxima._next_var_name())
try:
maxima.eval("declare(%s, %s)" % (repr(self._var), self._assumption))
# except TypeError, mess:
# if 'inconsistent' in str(mess): # note Maxima doesn't tell you if declarations are redundant
# raise ValueError, "Assumption is inconsistent"
except RuntimeError, mess:
if 'inconsistent' in str(mess): # note Maxima doesn't tell you if declarations are redundant
raise ValueError, "Assumption is inconsistent"
else:
raise
maxima.set("context", cur)
def assume(self):
"""
Make this assumption.
TESTS::
sage: from sage.symbolic.assumptions import GenericDeclaration
sage: decl = GenericDeclaration(x, 'even')
sage: decl.assume()
sage: cos(x*pi).simplify()
1
sage: decl2 = GenericDeclaration(x, 'odd')
sage: decl2.assume()
Traceback (most recent call last):
...
ValueError: Assumption is inconsistent
sage: decl.forget()
"""
if self in _assumptions:
return
from sage.calculus.calculus import maxima
cur = None
context = None
if self._context is None:
self._validate_feature()
cur = maxima.get("context")
# newcontext makes a fresh context that only has $global as
# a subcontext, and makes it the current $context,
# but does not deactivate other current contexts.
context = maxima.newcontext('context' + maxima._next_var_name())
must_declare = True
elif not maxima.featurep(self._var, self._assumption):
# Reactivating a previously active context.
# Run $declare again with the assumption
# to catch possible inconsistency
# with the active contexts.
cur = maxima.get("context")
# Redeclaring on the existing context does not seem to trigger
# inconsistency checking.
## maxima.set("context", self._context._maxima_init_())
# Instead, use a temporary context for this purpose
context = maxima.newcontext('context' + maxima._next_var_name())
must_declare = True
else:
must_declare = False
if must_declare:
try:
maxima.eval("declare(%s, %s)" %
(self._var._maxima_init_(), self._assumption))
except RuntimeError as mess:
if 'inconsistent' in str(
mess
): # note Maxima doesn't tell you if declarations are redundant
# Inconsistency with one of the active contexts.
raise ValueError("Assumption is inconsistent")
else:
raise
else:
if self._context is None:
self._context = context
context = None
finally:
assert cur is not None
maxima.set("context", cur)
if context is not None:
maxima.killcontext(context)
maxima.activate(self._context)
self._var.decl_assume(self._assumption)
_assumptions[self] = True