While
sage_eval('sin(x)')
does not work,
sage_eval('sin(x)', {'x': x})
does work. sage_eval needs to know the context (which variables have been
defined, etc.) in which to evaluate. I am not an expert, but
sage_eval('sin(x)', locals=locals())
might work pretty reliably, without having to specify each previously
defined variable by hand.
-- John
On Wednesday, April 26, 2023 at 12:05:03 AM UTC-7 Nasser M. Abbasi wrote:
> I can't use SR(sage_eval(' expression')) Now all my integral are
> failing.
> Here is an example
>
> >sage
> │ SageMath version 9.8, Release Date: 2023-02-11 │
> │ Using Python 3.11.1. Type "help()" for help. │
>
> sage: var('x')
> x
>
> sage: SR(sage_eval('sin(x)'))
> ---------------------------------------------------------------------------
> NameError Traceback (most recent call last)
> Cell In [3], line 1
> ----> 1 SR(sage_eval('sin(x)'))
>
> File ~/TMP/sage-9.8/src/sage/misc/sage_eval.py:198, in sage_eval(source,
> locals, cmds, preparse)
> 196 return locals['_sage_eval_returnval_']
> 197 else:
> --> 198 return eval(source, sage.all.__dict__, locals)
>
> File <string>:1
>
> NameError: name 'x' is not defined
>
>
> But
>
> sage: SR('sin(x)')
> sin(x)
>
> Works.
>
> So adding sage_eval() did not work.
>
> --Nasser
>
>
> On Wednesday, April 26, 2023 at 1:33:26 AM UTC-5 Nils Bruin wrote:
>
>> I think the problem is that the SR exression parses does not know about
>> python's "(a,b)" tuple notation. If you replace the round brackets with
>> square brackets, it does seem to work; at least for the example you give:
>>
>> sage: SR('hypergeometric([3/2,], [5/2, 3], -1/4*3^2)')
>> hypergeometric((3/2,), (5/2, 3), -1/4*3^2)
>>
>> You could use the python parser instead, via something like:
>>
>> SR(sage_eval(' hypergeometric((3/2,), (5/2, 3), -1/4*3^2)'))
>>
>> but note that SR will happily define symbols it doesn't know, whereas
>> sage_eval will complain:
>>
>> sage: SR("my_function(var1,var2)")
>> my_function(var1, var2)
>> sage: SR(sage_eval("my_function(var1,var2)"))
>> NameError: name 'my_function' is not defined
>>
>>
>>
>> On Tuesday, 25 April 2023 at 23:08:02 UTC-7 Nasser M. Abbasi wrote:
>>
>>> I read integrals from a file. They all are stored as strings.
>>>
>>> Then use SR('expression') inside sagemath to convert them to sagemath
>>> symbolic expression before calling integrate.
>>>
>>> Some give parsing error.
>>>
>>> Is using SR('expression') not the correct way to convert string to a
>>> symbolic expression?
>>>
>>> I am using 9.8 on Linux. Here is an example
>>>
>>> >sage
>>> │ SageMath version 9.8, Release Date: 2023-02-11 │
>>> │ Using Python 3.11.1. Type "help()" for help. │
>>>
>>> sage: hypergeometric((3/2,), (5/2, 3), -1/4*3^2)
>>> hypergeometric((3/2,), (5/2, 3), -9/4)
>>>
>>> You see, there is no error. But now if put the expression inside string
>>> and use SR, it gives error:
>>>
>>>
>>> sage: SR('hypergeometric((3/2,), (5/2, 3), -1/4*3^2)')
>>>
>>> ---------------------------------------------------------------------------
>>> SyntaxError Traceback (most recent call
>>> last)
>>> File ~/TMP/sage-9.8/src/sage/symbolic/expression.pyx:13706, in
>>> sage.symbolic.expression.new_Expression()
>>> 13705 from sage.calculus.calculus import
>>> symbolic_expression_from_string
>>> > 13706 return parent(symbolic_expression_from_string(x))
>>> 13707 except SyntaxError as err:
>>>
>>> File ~/TMP/sage-9.8/src/sage/calculus/calculus.py:2578, in
>>> symbolic_expression_from_string(s, syms, accept_sequence, parser)
>>> 2576 parser._callable_constructor().set_names({k[0]: v for k, v in
>>> syms.items()
>>> 2577 if _is_function(v)})
>>> -> 2578 return parse_func(s)
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:556, in
>>> sage.misc.parser.Parser.parse_expression()
>>> 555
>>> --> 556 cpdef parse_expression(self, s):
>>> 557 """
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:568, in
>>> sage.misc.parser.Parser.parse_expression()
>>> 567 cdef Tokenizer tokens = Tokenizer(s)
>>> --> 568 expr = self.p_expr(tokens)
>>> 569 if tokens.next() != EOS:
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:792, in
>>> sage.misc.parser.Parser.p_expr()
>>> 791 cdef int op
>>> --> 792 operand1 = self.p_term(tokens)
>>> 793 op = tokens.next()
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:826, in
>>> sage.misc.parser.Parser.p_term()
>>> 825 cdef int op
>>> --> 826 operand1 = self.p_factor(tokens)
>>> 827 op = tokens.next()
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:869, in
>>> sage.misc.parser.Parser.p_factor()
>>> 868 tokens.backtrack()
>>> --> 869 return self.p_power(tokens)
>>> 870
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:897, in
>>> sage.misc.parser.Parser.p_power()
>>> 896 """
>>> --> 897 operand1 = self.p_atom(tokens)
>>> 898 cdef int token = tokens.next()
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:952, in
>>> sage.misc.parser.Parser.p_atom()
>>> 951 func = self.callable_constructor(name)
>>> --> 952 args, kwds = self.p_args(tokens)
>>> 953 token = tokens.next()
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:989, in
>>> sage.misc.parser.Parser.p_args()
>>> 988 while token == c',':
>>> --> 989 arg = self.p_arg(tokens)
>>> 990 if isinstance(arg, tuple):
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:1039, in
>>> sage.misc.parser.Parser.p_arg()
>>> 1038 tokens.backtrack()
>>> -> 1039 return self.p_expr(tokens)
>>> 1040
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:792, in
>>> sage.misc.parser.Parser.p_expr()
>>> 791 cdef int op
>>> --> 792 operand1 = self.p_term(tokens)
>>> 793 op = tokens.next()
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:826, in
>>> sage.misc.parser.Parser.p_term()
>>> 825 cdef int op
>>> --> 826 operand1 = self.p_factor(tokens)
>>> 827 op = tokens.next()
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:869, in
>>> sage.misc.parser.Parser.p_factor()
>>> 868 tokens.backtrack()
>>> --> 869 return self.p_power(tokens)
>>> 870
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:897, in
>>> sage.misc.parser.Parser.p_power()
>>> 896 """
>>> --> 897 operand1 = self.p_atom(tokens)
>>> 898 cdef int token = tokens.next()
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:964, in
>>> sage.misc.parser.Parser.p_atom()
>>> 963 if token != c')':
>>> --> 964 self.parse_error(tokens, "Mismatched parentheses")
>>> 965 return expr
>>>
>>> File ~/TMP/sage-9.8/src/sage/misc/parser.pyx:1042, in
>>> sage.misc.parser.Parser.parse_error()
>>> 1041 cdef parse_error(self, Tokenizer tokens, msg="Malformed
>>> expression"):
>>> -> 1042 raise SyntaxError(msg, tokens.s, tokens.pos)
>>> 1043
>>>
>>> SyntaxError: Mismatched parentheses
>>>
>>> During handling of the above exception, another exception occurred:
>>>
>>> TypeError Traceback (most recent call
>>> last)
>>> Cell In [19], line 1
>>> ----> 1 SR('hypergeometric((3/2,), (5/2, 3), -1/4*3^2)')
>>>
>>> File ~/TMP/sage-9.8/src/sage/structure/parent.pyx:896, in
>>> sage.structure.parent.Parent.__call__()
>>> 894 if mor is not None:
>>> 895 if no_extra_args:
>>> --> 896 return mor._call_(x)
>>> 897 else:
>>> 898 return mor._call_with_args(x, args, kwds)
>>>
>>> File ~/TMP/sage-9.8/src/sage/structure/coerce_maps.pyx:161, in
>>> sage.structure.coerce_maps.DefaultConvertMap_unique._call_()
>>> 159 print(type(C), C)
>>> 160 print(type(C._element_constructor),
>>> C._element_constructor)
>>> --> 161 raise
>>> 162
>>> 163 cpdef Element _call_with_args(self, x, args=(), kwds={}):
>>>
>>> File ~/TMP/sage-9.8/src/sage/structure/coerce_maps.pyx:156, in
>>> sage.structure.coerce_maps.DefaultConvertMap_unique._call_()
>>> 154 cdef Parent C = self._codomain
>>> 155 try:
>>> --> 156 return C._element_constructor(x)
>>> 157 except Exception:
>>> 158 if print_warnings:
>>>
>>> File ~/TMP/sage-9.8/src/sage/symbolic/ring.pyx:384, in
>>> sage.symbolic.ring.SymbolicRing._element_constructor_()
>>> 382 TypeError: Malformed expression: λ + * !!! 1
>>> 383 """
>>> --> 384 return new_Expression(self, x)
>>> 385
>>> 386 def _force_pyobject(self, x, bint force=False, bint
>>> recursive=True):
>>>
>>> File ~/TMP/sage-9.8/src/sage/symbolic/expression.pyx:13709, in
>>> sage.symbolic.expression.new_Expression()
>>> 13707 except SyntaxError as err:
>>> 13708 msg, s, pos = err.args
>>> > 13709 raise TypeError("%s: %s !!! %s" % (msg, s[:pos],
>>> s[pos:]))
>>> 13710
>>> 13711 from sage.rings.infinity import (infinity, minus_infinity,
>>>
>>> TypeError: Mismatched parentheses: hypergeometric((3/2, !!! ), (5/2, 3),
>>> -1/4*3^2)
>>> sage:
>>>
>>>
>>>
>>> Is this a bug or Am I doing something wrong? This happens on very few
>>> cases, not all the time. The above is an example where SR gives an error.
>>>
>>> Thanks
>>> --Nasser
>>>
>>>
--
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