AskSage results to json about pg

[dpvc]

Just FYI, the MathObject Real stores the same number of digits as perl reals, but it only displays fewer. It uses the %g format for sprintf() by default, which gives 6 digits of precision. You could change that to get more (or fewer).

[FloraHerzner]

Thank you for pointing that out. So the number of digits actually differs. repr(o) gives a higher precision than float(o). But is it nessecary to limit the number of digits for some reason?

[dpvc]

I don't believe there is any reason to limit the number. The internal format stores about 17 digits of precision (it actually uses 54 binary digits, and that gives 16 to 17 digits of precision in base 10, depending on the number being represented -- the conversion doesn't match up with decimal digits precisely). So if repr(0) produces 17 or more, then that is the best you can do.

[heiderich]

As I understand it, this function _webwork_safe_json is used to as a convenience function to convert Sage objects into JSON objects that can be interpreted properly by WeBWorK. This is necessary, since the standard representations of Sage objects are not JSON compatible. For instance we have:

• For floats:

print float(pi)
print repr(pi)

returns

3.14159265359
pi

• For elements of free modules:

M = FreeModule(base_ring=QQ,rank=2)
v = M([1,0])
print list(v)
print repr(v)

returns

[1, 0]
(1, 0)

• For matrices:

I = matrix.identity(2)
print [list(i) for i in I.rows()]
print repr(I)

returns

[[1, 0], [0, 1]]
[1 0]
[0 1]

So the last case handled in

elif isinstance(o, SageObject):
                json_obj = repr(o)

seems not to cover the cases treated before.