My objective is to concisely define an expression with variables,
assign values to the variables, and then compute the answer.
Here is what I did today:
┌────────────────────────────────────────────────────────────────────┐
│ SageMath version 9.3.rc4, Release Date: 2021-04-18 │
│ Using Python 3.9.2. Type "help()" for help. │
└────────────────────────────────────────────────────────────────────┘
┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
┃ Warning: this is a prerelease version, and it may be unstable. ┃
┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
sage: z = SR.var('z')
sage: i = 2 * z
sage: i
2*z
sage: z
z
sage: type(i)
<class 'sage.symbolic.expression.Expression'>
sage: type(z)
<class 'sage.symbolic.expression.Expression'>
sage: z = random_prime(100)
sage: z
79
sage: type(z)
<class 'sage.rings.integer.Integer'>
sage: i
2*z
sage: valuation(i)
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
/var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/arith/misc.py
in valuation(m, *args, **kwds)
743 try:
--> 744 return m.valuation(*args, **kwds)
745 except AttributeError:
/var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/structure/element.pyx
in sage.structure.element.Element.__getattr__
(build/cythonized/sage/structure/element.c:4709)()
492 """
--> 493 return self.getattr_from_category(name)
494
/var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/structure/element.pyx
in sage.structure.element.Element.getattr_from_category
(build/cythonized/sage/structure/element.c:4821)()
505 cls = P._abstract_element_class
--> 506 return getattr_from_other_class(self, cls, name)
507
/var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/cpython/getattr.pyx
in sage.cpython.getattr.getattr_from_other_class
(build/cythonized/sage/cpython/getattr.c:2619)()
371 dummy_error_message.name = name
--> 372 raise AttributeError(dummy_error_message)
373 attribute = <object>attr
AttributeError: 'sage.symbolic.expression.Expression' object has no
attribute '__custom_name'
During handling of the above exception, another exception occurred:
TypeError Traceback (most recent call last)
/var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/symbolic/expression.pyx
in sage.symbolic.expression.Expression._integer_
(build/cythonized/sage/symbolic/expression.cpp:8808)()
1298 try:
-> 1299 n = self.pyobject()
1300 except TypeError:
/var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/symbolic/expression.pyx
in sage.symbolic.expression.Expression.pyobject
(build/cythonized/sage/symbolic/expression.cpp:6143)()
586 if not is_a_numeric(self._gobj):
--> 587 raise TypeError("self must be a numeric expression")
588 return py_object_from_numeric(self._gobj)
TypeError: self must be a numeric expression
During handling of the above exception, another exception occurred:
TypeError Traceback (most recent call last)
<ipython-input-11-227398a9d1bf> in <module>
----> 1 valuation(i)
/var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/arith/misc.py
in valuation(m, *args, **kwds)
744 return m.valuation(*args, **kwds)
745 except AttributeError:
--> 746 return ZZ(m).valuation(*args, **kwds)
747
748
/var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/structure/parent.pyx
in sage.structure.parent.Parent.__call__
(build/cythonized/sage/structure/parent.c:9335)()
896 if mor is not None:
897 if no_extra_args:
--> 898 return mor._call_(x)
899 else:
900 return mor._call_with_args(x, args, kwds)
/var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/structure/coerce_maps.pyx
in sage.structure.coerce_maps.NamedConvertMap._call_
(build/cythonized/sage/structure/coerce_maps.c:6042)()
285 raise TypeError("Cannot coerce {} to {}".format(x, C))
286 cdef Map m
--> 287 cdef Element e = method(C)
288 if e is None:
289 raise RuntimeError("BUG in coercion model: {} method of
{} returned None".format(self.method_name, type(x)))
/var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/symbolic/expression.pyx
in sage.symbolic.expression.Expression._integer_
(build/cythonized/sage/symbolic/expression.cpp:8857)()
1299 n = self.pyobject()
1300 except TypeError:
-> 1301 raise TypeError("unable to convert %r to an integer" %
self)
1302 if isinstance(n, sage.rings.integer.Integer):
1303 return n
TypeError: unable to convert 2*z to an integer
sage:
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