eq: giving TypeError: cannot determine truth value of Relational

[cbm755]

On SymPy 1.9:

>> eqn = 2*x + 7 == 17
error: Python exception: TypeError: cannot determine truth value of Relational
    occurred at line 16 of the Python code block:
    q[i] = _op(*[k[i] if isinstance(k, MatrixBase) else k for k in _ins])
error: called from
    pycall_sympy__ at line 178 column 7
    elementwise_op at line 99 column 5
    ineq_helper at line 35 column 5
    eq at line 91 column 5

Same for eq(2*x+7, 17). This is leading to a lot of test failures.

Might be useful to determine the behaviour on 1.6, 1.7, 1.8 as well

[cbm755]

Works on 1.8

[cbm755]

MWE in SymPy

x = Symbol('x')
e = Eq(2*x, 7)
A = Matrix([[e]])      # you are no longer allowed to keep an Eq inside a Matrix

We get the warning from #1052.

/home/cbm/work/octsympy/octsympy.git/inst/sympy/matrices/repmatrix.py:98: SymPyDeprecationWarning: 

non-Expr objects in a Matrix has been deprecated since SymPy 1.9. Use
list of lists, TableForm or some other data structure instead. See
https://github.com/sympy/sympy/issues/21497 for more info.

  SymPyDeprecationWarning(

But A is still valid (its "just" a warning):

>>> A
Matrix([[Eq(2*x, 7)]])

But if you assign e to a existing Matrix its an error:

>>> B = Matrix([[42]])                                                                                             
>>> B[0]        # good
42
>>> B[0] = 7    # fine
>>> B[0] = e      # <--  our elementwise_op does this

...inst/sympy/matrices/repmatrix.py:85: SymPyDeprecationWarning: 

non-Expr objects in a Matrix has been deprecated since SymPy 1.9. Use
list of lists, TableForm or some other data structure instead. See
https://github.com/sympy/sympy/issues/21497 for more info.

  SymPyDeprecationWarning(
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-33-c093b1f7650a> in <module>
----> 1 B[0] = e

~/work/octsympy/octsympy.git/inst/sympy/matrices/repmatrix.py in __setitem__(self, key, value)
    390             i, j, value = rv
    391             self._rep, value = self._unify_element_sympy(self._rep, value)
--> 392             self._rep.rep.setitem(i, j, value)
    393 
    394     def _eval_col_del(self, col):

~/work/octsympy/octsympy.git/inst/sympy/polys/matrices/sdm.py in setitem(self, i, j, value)
     94             raise IndexError("index out of range")
     95         i, j = i % m, j % n
---> 96         if value:
     97             try:
     98                 self[i][j] = value

~/work/octsympy/octsympy.git/inst/sympy/core/relational.py in __bool__(self)
    396 
    397     def __bool__(self):
--> 398         raise TypeError("cannot determine truth value of Relational")
    399 
    400     def _eval_as_set(self):

TypeError: cannot determine truth value of Relational

I'm not sure if this is a bug upstream but its certainly clear we are not supposed to be storing Eq inside matrices any more...

[cbm755]

Most (all?) of these have been worked around, closing in favour of #1124 where we look for a more permanent solution