8000 gh-81313: Add the intmath module (PEP-791) by serhiy-storchaka · Pull Request #133909 · python/cpython · GitHub
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99 changes: 99 additions & 0 deletions Doc/library/imath.rst
Original file line number Diff line number Diff line change
@@ -0,0 +1,99 @@
:mod:`imath` --- Mathematical functions for integer numbers
===========================================================

.. module:: imath
:synopsis: Mathematical functions for integer numbers.

.. versionadded:: next

--------------

This module provides access to the mathematical functions for integer arguments.
These functions accept integers and objects that implement the
:meth:`~object.__index__` method which is used to convert the object to an integer
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In the same way we could simplify now description of argument processing in the math module. Except for a special snowflake "log" - all use PyFloat_AsDouble(). (Well, few functions also try special dunder methods.)

Though, probably it's for following prs.

number. They cannot be used with floating-point numbers or complex
numbers.

The following functions are provided by this module. All return values are
integers.


.. function:: comb(n, k)

Return the number of ways to choose *k* items from *n* items without repetition
and without order.

Evaluates to ``n! / (k! * (n - k)!)`` when ``k <= n`` and evaluates
to zero when ``k > n``.

Also called the binomial coefficient because it is equivalent
to the coefficient of k-th term in polynomial expansion of
``(1 + x)ⁿ``.

Raises :exc:`TypeError` if either of the arguments are not integers.
Raises :exc:`ValueError` if either of the arguments are negative.


.. function:: factorial(n)

Return *n* factorial as an integer. Raises :exc:`ValueError` if *n* is not integral or
is negative.


.. function:: gcd(a, b)

Return the greatest common divisor of the specified integer arguments.
If any of the arguments is nonzero, then the returned value is the largest
positive integer that is a divisor of all arguments. If all arguments
are zero, then the returned value is ``0``. ``gcd()`` without arguments
returns ``0``.


.. function:: ilog2(n)

Return the integer base 2 logarithm of the positive integer *n*. This is the
floor of the exact base 2 logarithm root of *n*, or equivalently the
greatest integer *k* such that
2\ :sup:`k` |nbsp| ≤ |nbsp| *n* |nbsp| < |nbsp| 2\ :sup:`k+1`.

It is equivalent to ``n.bit_length() - 1`` for positive *n*.


.. function:: isqrt(n)

Return the integer square root of the nonnegative integer *n*. This is the
floor of the exact square root of *n*, or equivalently the greatest integer
*a* such that *a*\ ² |nbsp| ≤ |nbsp| *n*.

For some applications, it may be more convenient to have the least integer
*a* such that *n* |nbsp| ≤ |nbsp| *a*\ ², or in other words the ceiling of
the exact square root of *n*. For positive *n*, this can be computed using
``a = 1 + isqrt(n - 1)``.


.. function:: lcm(*integers)

Return the least common multiple of the specified integer arguments.
If all arguments are nonzero, then the returned value is the smallest
positive integer that is a multiple of all arguments. If any of the arguments
is zero, then the returned value is ``0``. ``lcm()`` without arguments
returns ``1``.


.. function:: perm(n, k=None)

Return the number of ways to choose *k* items from *n* items
without repetition and with order.

Evaluates to ``n! / (n - k)!`` when ``k <= n`` and evaluates
to zero when ``k > n``.

If *k* is not specified or is ``None``, then *k* defaults to *n*
and the function returns ``n!``.

Raises :exc:`TypeError` if either of the arguments are not integers.
Raises :exc:`ValueError` if either of the arguments are negative.


.. |nbsp| unicode:: 0xA0
:trim:
55 changes: 9 additions & 46 deletions Doc/library/math.rst
Original file line number Diff line number Diff line change
Expand Up @@ -124,40 +124,27 @@ noted otherwise, all return values are floats.
Number-theoretic functions
--------------------------

.. function:: comb(n, k)

Return the number of ways to choose *k* items from *n* items without repetition
and without order.

Evaluates to ``n! / (k! * (n - k)!)`` when ``k <= n`` and evaluates
to zero when ``k > n``.
These functions are aliases of corresponding functions in the
:mod:`imath` module.

Also called the binomial coefficient because it is equivalent
to the coefficient of k-th term in polynomial expansion of
``(1 + x)ⁿ``.
.. function:: comb(n, k)

Raises :exc:`TypeError` if either of the arguments are not integers.
Raises :exc:`ValueError` if either of the arguments are negative.
An alias of :func:`imath.comb`.

.. versionadded:: 3.8


.. function:: factorial(n)

Return *n* factorial as an integer. Raises :exc:`ValueError` if *n* is not integral or
is negative.
An alias of :func:`imath.factorial`.

.. versionchanged:: 3.10
Floats with integral values (like ``5.0``) are no longer accepted.


.. function:: gcd(*integers)

Return the greatest common divisor of the specified integer arguments.
If any of the arguments is nonzero, then the returned value is the largest
positive integer that is a divisor of all arguments. If all arguments
are zero, then the returned value is ``0``. ``gcd()`` without arguments
returns ``0``.
An alias of :func:`imath.gcd`.

.. versionadded:: 3.5

Expand All @@ -168,42 +155,21 @@ Number-theoretic functions

.. function:: isqrt(n)

Return the integer square root of the nonnegative integer *n*. This is the
floor of the exact square root of *n*, or equivalently the greatest integer
*a* such that *a*\ ² |nbsp| ≤ |nbsp| *n*.

For some applications, it may be more convenient to have the least integer
*a* such that *n* |nbsp| ≤ |nbsp| *a*\ ², or in other words the ceiling of
the exact square root of *n*. For positive *n*, this can be computed using
``a = 1 + isqrt(n - 1)``.
An alias of :func:`imath.isqrt`.

.. versionadded:: 3.8


.. function:: lcm(*integers)

Return the least common multiple of the specified integer arguments.
If all arguments are nonzero, then the returned value is the smallest
A3E2 positive integer that is a multiple of all arguments. If any of the arguments
is zero, then the returned value is ``0``. ``lcm()`` without arguments
returns ``1``.
An alias of :func:`imath.lcm`.

.. versionadded:: 3.9


.. function:: perm(n, k=None)

Return the number of ways to choose *k* items from *n* items
without repetition and with order.

Evaluates to ``n! / (n - k)!`` when ``k <= n`` and evaluates
to zero when ``k > n``.

If *k* is not specified or is ``None``, then *k* defaults to *n*
and the function returns ``n!``.

Raises :exc:`TypeError` if either of the arguments are not integers.
Raises :exc:`ValueError` if either of the arguments are negative.
An alias of :func:`imath.perm`.

.. versionadded:: 3.8

Expand Down Expand Up @@ -838,6 +804,3 @@ Constants

Module :mod:`cmath`
Complex number versions of many of these functions.

.. |nbsp| unicode:: 0xA0
:trim:
6 changes: 5 additions & 1 deletion Doc/whatsnew/3.15.rst
Original file line number Diff line number Diff line change
Expand Up @@ -83,7 +83,11 @@ Other language changes
New modules
===========

* None yet.
imath
-----

This module provides access to the mathematical functions for integer arguments.
(Contributed by Serhiy Storchaka in :gh:`81313`.)
Comment on lines +89 to +90
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Suggested change
This module provides access to the mathematical functions for integer arguments.
(Contributed by Serhiy Storchaka in :gh:`81313`.)
This module provides access to the mathematical functions for integer
arguments (:pep:`791`).
(Contributed by Serhiy Storchaka in :gh:`81313`.)



Improved modules
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