I have 8 bytes expressed as integer values stored in a list.
They correspond to a 64-bit counter with the lowest significant byte at first position.
Here is an example what I am doing:
byteIntegers = {123, 12, 0, 169, 255, 20, 67, 199};
counter=Total[Table[byteIntegers[[i]]*256^(i - 1), {i, 1, 8}]]
14358343125271841915
How would you calculate this value?
You can use
FromDigits[Reverse[byteIntegers], 256]
because the elements of the list can be considered digits of a number expressed in base 256.
If we did not have this function, we could also use
Total[byteIntegers 256^(Range@Length[byteIntegers] - 1)]
Whether you find this better than the Table version depends on taste.
FromDigits function did not exist. This is how I would implement it. But your Table solution is more readable for those not used to the style of mine. You could change Total@Table[...] to Sum[...], which would be shorter, but personally I don't like that because I tend to think of Sum as a symbolic processing function. We could also do Total@MapIndexed[#1 256^(First[#2] - 1) &, byteIntegers], but it feels too convoluted to me. A similar solution can also be constructed with MapThread.
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– Szabolcs
Feb 26 '17 at 11:27
Inner[#1 256^#2 &, byteIntegers, Range@Length[byteIntegers] - 1], which looks clever, but I need a second before I understand what it actually does. As usual, Mathematica has myriads of ways. The two ways I like the most (after FromDigits, which is the clear winner) are what you showed and my second solution.
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– Szabolcs
Feb 26 '17 at 11:28
