diff options
| -rw-r--r-- | Doc/library/stdtypes.rst | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst index 2e551dc..e6f7b2c 100644 --- a/Doc/library/stdtypes.rst +++ b/Doc/library/stdtypes.rst @@ -382,7 +382,7 @@ modules. .. _bitstring-ops: Bitwise Operations on Integer Types --------------------------------------- +----------------------------------- .. index:: triple: operations on; integer; types @@ -396,9 +396,9 @@ Bitwise Operations on Integer Types operator: >> operator: ~ -Bitwise operations only make sense for integers. Negative numbers are treated -as their 2's complement value (this assumes that there are enough bits so that -no overflow occurs during the operation). +Bitwise operations only make sense for integers. The result of bitwise +operations is calculated as though carried out in two's complement with an +infinite number of sign bits. The priorities of the binary bitwise operations are all lower than the numeric operations and higher than the comparisons; the unary operation ``~`` has the @@ -409,13 +409,13 @@ This table lists the bitwise operations sorted in ascending priority: +------------+--------------------------------+----------+ | Operation | Result | Notes | +============+================================+==========+ -| ``x | y`` | bitwise :dfn:`or` of *x* and | | +| ``x | y`` | bitwise :dfn:`or` of *x* and | (4) | | | *y* | | +------------+--------------------------------+----------+ -| ``x ^ y`` | bitwise :dfn:`exclusive or` of | | +| ``x ^ y`` | bitwise :dfn:`exclusive or` of | (4) | | | *x* and *y* | | +------------+--------------------------------+----------+ -| ``x & y`` | bitwise :dfn:`and` of *x* and | | +| ``x & y`` | bitwise :dfn:`and` of *x* and | (4) | | | *y* | | +------------+--------------------------------+----------+ | ``x << n`` | *x* shifted left by *n* bits | (1)(2) | @@ -438,6 +438,12 @@ Notes: A right shift by *n* bits is equivalent to division by ``pow(2, n)`` without overflow check. +(4) + Performing these calculations with at least one extra sign extension bit in + a finite two's complement representation (a working bit-width of + ``1 + max(x.bit_length(), y.bit_length()`` or more) is sufficient to get the + same result as if there were an infinite number of sign bits. + Additional Methods on Integer Types ----------------------------------- |