Thinking about numbers in the 01_ programming language, the natural way to represent integers would be to use little-endian base 2. To further simplify things, consider only infinite lists of bits. So the important numbers are

zero = 0 zero.
one = 1 zero.

Negative numbers can also be represented

-one = 1 -one.

Integer addition can be defined as

+/integer 0a 0b = 0 +/integer a b.
+/integer 1a 0b = 1 +/integer a b.
+/integer 0a 1b = 1 +/integer a b.
+/integer 1a 1b = 0 +/integer/carry a b.

where integer addition with carry is

+/integer/carry 0a 0b = 1 +/integer a b.
+/integer/carry 1a 0b = 0 +/integer/carry a b.
+/integer/carry 0a 1b = 0 +/integer/carry a b.
+/integer/carry 1a 1b = 1 +/integer/carry a b.

And integer subtraction is

-/integer 0a 0b = 0 -/integer a b.
-/integer 1a 0b = 1 -/integer a b.
-/integer 0a 1b = 1 -/integer/borrow a b.
-/integer 1a 1b = 0 -/integer a b.

where integer subtraction with borrow is

-/integer/borrow 0a 0b = 1 -/integer/borrow a b.
-/integer/borrow 1a 0b = 0 -/integer a b.
-/integer/borrow 0a 1b = 0 -/integer/borrow a b.
-/integer/borrow 1a 1b = 1 -/integer/borrow a b.