> On Jul 18, 2015, at 1:34 PM, Mark Lawrence <[email protected]> wrote:
>
>
[byte]
> What is an {HP calculator} roll operation?
>
The original Hewlett Packard “Scientific” calculators (HP-35, 45, 65, etc) that
used Polish notation (operand, operand, operation; with no “=“ sign) had a
stack. That stack itself could be manipulated (e.g., interchange X and Y). One
of the stack manipulation commands was “Roll” which moved the top entry into X
and pushed remaining elements up one. Later versions had both Roll-up and
Roll-down, Roll-down moved the X entry to the top of the stack and dropped the
other elements.
Bill (Who still uses an HP-45 emulator on his iPhone)
> --
> My fellow Pythonistas, ask not what our language can do for you, ask
> what you can do for our language.
>
> Mark Lawrence
>
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