BCD List to HEX List

[bryanjugglercryptographer at yahoo.com]

John Machin wrote:
> bryanjugglercryptographer at yahoo.com wrote:
>
> >My version assumes three subroutines: extracting
> > nibbles, shifting, and adding, Those are pretty simple, so I asked
> > if he needed them rather than presenting them.
> > Assuming we have
> > them, the algorithm is three lines long.
>
> Perhaps you could enlighten us by publishing (a) the spec for each of
> the get_nibble(s), shift, and add subroutines (b) the three-line
> algorithm (c) what the algorithm is intended to achieve ...

"For each nibble n of x" means to take each 4 bit piece of the BCD
integer as a value from zero to sixteen (though only 0 through 9
will appear), from most significant to least significant. "Adding"
integers and "shifting" binary integers is well-defined
terminology. I already posted the three-line algorithm. It
appeared immediately under the phrase "To turn BCD x to binary
integer y," and that is what it is intended to achieve.

> > He took a while to state the problem, but was clear from the start
> > that he had lists of digits rather than an integer datatype.
>
> Yes, input was a list [prototyping a byte array] of decimal digits. The
> OUTPUT was also a list of something. A few messages later, it became
> clear that the output desired was a list of hexadecimal digits. Until
> he revealed that the input was up to 24 decimal digits,  I was pursuing
> the notion that a solution involving converting decimal to binary (in a
> 32-bit long) then to hexadecimal was the way to go.
>
> What is apparently needed is an algorithm for converting a "large"
> number from a representation of one base-10 digit per storage unit to
> one of a base-16  digit per storage unit,  when the size of the number
> exceeds the size (8, 16, 32, etc bits) of the "registers" available.

I read his "Yes I realized that after writing it." response to
Dennis Lee Bieber to mean Bieber was correct and what he wanted
was to go from BCD to a normal binary integer, which is base 256.

The point of posting the simple high-level version of the
algorithm was to show a general form that works regardless of
particular languages, register sizes and storage considerations.
Those matters can effect the details of how one shifts a binary
integer left one bit, but shifting is not complicated in any
plausible case.

> Is that what you have?

I'm sorry my post so confused, and possibly offended you.


-- 
--Bryan