A simple Python project where numbers are represented by strings. No ints, longs, or floats are used, nor any function that returns a value of any of these types. Computations are performed through string manipulations only. No integers are used in indexing strings or arrays.

Numbers are signed integers represented as 32-bit binary strings. Overflow and underflow may occur just as in ordinary 32-bit integer computations. Operations supported are: negation, addition, subtraction, multiplication, division, modulo, divmod, and left and right shifts. The operators +, -, *, /, %, <<, and >> may be used to invoke these operations. Comparisons may be invoked using <, <=, ==, >=, and >.

Example:

>>> print(StrNum('13') * StrNum('1071'))
13923
>>> print((StrNum('-1024') >> StrNum('2')) * StrNum('12') + StrNum('15'))
-3057
>>> print('q = %s, r = %s' % divmod(StrNum('21809'), StrNum('101')))
q = 215, r = 94

These calculations may be verified using ordinary arithmetic:

>>> 13 * 1071
13923
>>> (-1024 >> 2) * 12 + 15
-3057
>>> divmod(21809, 101)
(215, 94)

The code also provides example implementations of the functions multmod and powmod, which are identical to the implementations of these functions using ordinary arithmetic except that the strmath equivalents of certain constants are used. For example, zero and one is used instead of 0 and 1. Note that zero is defined as StrNum('0') and one is defined as StrNum('1').

Example:

>>> print(powmod(StrNum('23'), StrNum('12345'), StrNum('700')))
43

This result may be verified using the built-in function pow:

>>> pow(23, 12345, 700)
43