Hi. I think that I have come across a bug in
sage.calculus.calculus.SymbolicArithmetic.substitute_over_ring
The first three examples below work, but the fourth does not. It seems
that sage can coerce Integers(10)(3) into a symbolic expression, but
only when it is passed as a keyword argument.
I'm not sure what is going on here, but when R = Integers(10), an
explicit conversion such as SymbolicExpressionRing(R(3)) does not work
either (I'm not claiming that it should). I think that is why the fourth
example below doesn't work. I don't know how the third example does
work, however.
sage: R = Integers(10)
sage: x = var('x')
sage: expression = 3*x
sage: expression.substitute_over_ring(x=3,ring=R)
9
sage: expression.substitute_over_ring(3,ring=R)
9
sage: expression.substitute_over_ring(x=R(3),ring=R)
9
sage: expression.substitute_over_ring(R(3),ring=R)
---------------------------------------------------------------------------
<type 'exceptions.TypeError'> Traceback (most recent call last)
/home/bober/math/talof/<ipython console> in <module>()
/home/bober/sage/local/lib/python2.5/site-packages/sage/calculus/calculus.py in
substitute_over_ring(self, in_dict, ring, **kwds)
2052 def substitute_over_ring(self, in_dict=None, ring=None, **kwds):
2053 X = self.simplify()
-> 2054 kwds = self.__parse_in_dict(in_dict, kwds)
2055 kwds = self.__varify_kwds(kwds)
2056 if ring is None:
/home/bober/sage/local/lib/python2.5/site-packages/sage/calculus/calculus.py in
__parse_in_dict(self, in_dict, kwds)
2034 if len(kwds) > 0:
2035 raise ValueError, "you must not both give the variable
and specify it explicitly when doing a substitution."
-> 2036 in_dict = SR(in_dict)
2037 vars = self.variables()
2038 #if len(vars) > 1:
/home/bober/sage/local/lib/python2.5/site-packages/sage/calculus/calculus.py in
__call__(self, x)
313 elif hasattr(x, '_symbolic_'):
314 return x._symbolic_(self)
--> 315 return self._coerce_impl(x)
316
317 def _coerce_impl(self, x):
/home/bober/sage/local/lib/python2.5/site-packages/sage/calculus/calculus.py in
_coerce_impl(self, x)
342 return
evaled_symbolic_expression_from_maxima_string('%s+%%i*%s'%(x.real,x.imag))
343 else:
--> 344 raise TypeError, "cannot coerce type '%s' into a
SymbolicExpression."%type(x)
345
346 def _repr_(self):
<type 'exceptions.TypeError'>: cannot coerce type '<type
'sage.rings.integer_mod.IntegerMod_int'>' into a SymbolicExpression.
sage:
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