import proveit
# Prepare this notebook for defining the axioms of a theory:
%axioms_notebook # Keep this at the top following 'import proveit'.
from proveit import Literal
from proveit import n, x
from proveit.logic import Equals, Forall, And, InSet
from proveit.numbers import num, zero, one, Add, LessEq, Natural
from proveit.numbers.numerals.decimals import DecimalSequence, Digits
%begin axioms
one_def = Equals(num(1), Add(zero, one))
two_def = Equals(num(2), Add(one, one))
three_def = Equals(num(3), Add(num(2), one))
four_def = Equals(num(4), Add(num(3), one))
five_def = Equals(num(5), Add(num(4), one))
six_def = Equals(num(6), Add(num(5), one))
seven_def = Equals(num(7), Add(num(6), one))
eight_def = Equals(num(8), Add(num(7), one))
nine_def = Equals(num(9), Add(num(8), one))
#\forall_{n} (n \in N_{\leq 9}) = (n \in N and n \leq 9)
N_leq_9_def = Forall(n, Equals(InSet(n, Digits), And(InSet(n, Natural), LessEq(n, num(9)))))
single_digit_reduction = Forall(n, Equals(DecimalSequence(n), n), domain=Digits)
%end axioms