Did you ever saw a char and thought: "Damn, 1 byte for a single char is pretty darn inefficient"? No? Well I did. So what I decided to do instead is to pack 5 chars, convert each char to a 2 digit integer and then concat those 5 2 digit ints together into one big unsigned int and boom, I saved 5 chars using only 4 instead of 5 bytes. The reason this works is, because one unsigned int is a ten digit long number and so I can save one char using 2 digits. In theory you could save 32 different chars using this technique (the first two digits of an unsigned int are 42 and if you dont want to account for a possible 0 in the beginning you end up with 32 chars). If you would decide to use all 10 digits you could save exactly 3 chars. Why should anyone do that? Idk. Is it way to much work to be useful? Yes. Was it funny? Yes.

Anyone whos interested in the code: Heres how I did it in C: https://pastebin.com/hDeHijX6

Yes I know, the code is probably bad, but I do not care. It was just a funny useless idea I had.

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[–] cows_are_underrated@feddit.org 2 points 7 hours ago (1 children)

Just stupid

[–] ChaoticNeutralCzech@feddit.org 1 points 6 hours ago* (last edited 6 hours ago) (2 children)

If you couldn't write

if(pChar >= 'a' && pChar <= 'z') return pChar - ('a' - 10);

I suppose you typed this "all the size of a lookup table with none of the speed" abomination manually too.

[–] Zacryon@feddit.org 2 points 5 hours ago (1 children)

switch case structures are very efficient in c and c++. They work similarly like an offset into memory. Compute the offset once (any expression in the 'case' lines), then jump. Using primitives directly, like here with chars, is directly the offset. Contrary to if-else branches, where each case must be evaluated first and the CPU has basically no-op cycles in the pipeline until the result of the branch is known. If it fails, it proceeds with the next one, waits again etc.. (Some CPU architectures might have stuff like speculative branch execution, which can speed this up.)

However, code-style wise this is really not elegant and something like your proposal or similar would be much better.

[–] ChaoticNeutralCzech@feddit.org 1 points 4 hours ago* (last edited 2 hours ago)

Oh, I didn't know that they were a LUT of jump addresses. Stil, a LUT of values would be more space-efficient and likely faster. Also, what if the values are big and sparse, e.g.

switch (banknoteValue) {
    case 5000:
        check_uv();
        check_holograph();
    case 2000:
        check_stripe();
    case 1000:
        check_watermark();
}

...does the compiler make it into an if-else-like machine code instead?

[–] cows_are_underrated@feddit.org 1 points 6 hours ago

Yes, I did type it out manually (not really, I just copy pasted it and changed the according values)