Etuplize Python lists using `cons`

[rlouf]

etuplize currently transforms a Python list to an expression tuple that contains the elements of the list:

from etuples import etuplize
from etuples.core import InvalidExpression

et = etuplize([1, 2])
print(et)
# e(1, 2)

This expression tuple is invalid and cannot be evaluated:

try:
    et.evaled_obj
except InvalidExpression as e:
    print(e)
# ExpressionTuple does not have a callable operator.

I thus suggest that etuplize returns the following expression that uses cons, which can be emulated by registering _car and _cdr from cons.core for lists:

from cons.core import _car, _cdr, cons
from etuples import etuple

@_car.register(list)
def car_list(x):
    return cons

@_cdr.register(list)
def cdr_list(x):
    return etuple(*x, [])

et = etuplize([1, 2])
print(et)
# e(<class 'cons.core.ConsPair'>, 1, 2, [])

[brandonwillard]

The question is whether or not etuplize(x).evaled_obj == x should always hold, and I want to say "yes", but I'm not entirely sure.