Re: BCD List to HEX List


John Machin wrote:
bryanjugglercryptographer@xxxxxxxxx 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

.

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