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Eight, Nine, Ten...

Started by MilchoPenchev Mar 18, 2013 at 4:28 PM 31 replies 10.4k views
Original Post
MilchoPenchev
MilchoPenchev

Excerpt from code I recently saw:


#define EIGHT  (0x08) 
#define NINE   (0x09) 
#define TEN    (0x10) 

. . .

I hope I wasn't too subtle - the definition of TEN is what is ... interesting here.

MilchoPenchev
MilchoPenchev


edit:
Oh gosh, I didn't even realize the TEN issue... That's horrible.

That edit made my day :D - that is exactly why this is so scary.

Rattrap
Rattrap

an explanation for the more noobish of us? what's wrong with that definition? >_<;

0x10 in 16 in hex.

"I can't believe I'm defending logic to a turing machine." - Kent Woolworth [Other Space]
Paradigm Shifter
Paradigm Shifter

Could be binary coded decimal... and it makes outputting a text value easier as well ;)

Manic Miner on the ZX Spectrum didn't even store the game score or high score in a variable... it just used ASCII text on the screen (the screen area where the score was displayed was never cleared).

The algorithm only added to your score either 1 or 10 or 100 at a time IIRC. It just increased the ASCII value at the screen position by 1 and if that makes it > 9 it made the current digit 0 and added 1 to the next digit along (and looped if that was bumped to > 9 as well).

It then just copied the score to the high score location if the score was larger than the current high score (check was done with another ASCII comparison).

"Most people think, great God will come from the sky, take away everything, and make everybody feel high" - Bob Marley
MilchoPenchev
MilchoPenchev


Could be binary coded decimal... [snip]

That sounds so convoluted it requires its own thread.

Unfortunately that wasn't the case here - this code, according to a colleague who originally fixed it - caused a fatal crash in the software.

Adaline
Adaline

Obvious, the coder has 8 fingers on each hand

cr88192
cr88192

Obvious, the coder has 8 fingers on each hand

... maybe the use of named constants is what was at fault here ...

...
#define FOURTY_TWO (042)
#define NINETEEN_EIGHTY_FOUR (NINETEEN, EIGHTY, FOUR)
...
21st Century Moose
21st Century Moose

#define FOURTY_TWO (042)

That's even worse!!!

Direct3D has need of instancing, but we do not. We have plenty of glVertexAttrib calls. 
Bacterius
Bacterius

That's even worse!!!

This used to happen to me when I was trying to align constants properly. Nowadays I just put spaces instead, been burned too often by this damn octal notation "feature" which I'm guessing nobody actually uses, except the odd raw socket hacker (if even). Permission bits are another one, but constants for those are already defined anyway.

“If I understand the standard right it is legal and safe to do this but the resulting value could be anything.”
cr88192
cr88192


That's even worse!!!

This used to happen to me when I was trying to align constants properly. Nowadays I just put spaces instead, been burned too often by this damn octal notation "feature" which I'm guessing nobody actually uses, except the odd raw socket hacker (if even). Permission bits are another one, but constants for those are already defined anyway.


at one point I made things more orthogonal (for my script language) by adding several number notations:
0b... //binary
0c... //octal
0d... //decimal
in addition to:
0x... //hexadecimal

then got into a big mental debate as to whether or not to keep '0' by itself as an octal prefix, make it decimal, or maybe just deprecate it and issue a warning...

note, '_' is also a spacer, so:
0d999_999_999
is the same as:
999999999

likewise:
0x5CD13A42_3B9AC9FFL
or:
999_999_999_999_999_999L
or:
0x0DE0_B6B3__A763_FFFFL
Sik_the_hedgehog
Sik_the_hedgehog

Octal was big back in the day when C was being made, maybe even moreso than hexadecimal. These days nobody really uses it since it can't be aligned nicely to 8-bit (some computers back then had words with a bit count multiple of 3, so octal probably made a lot more of sense).

Don't pay much attention to "the hedgehog" in my nick, it's just because "Sik" was already taken =/ By the way, Sik is pronounced like seek, not like sick.
Cornstalks
Cornstalks

But they could have made it useful by adding pluses!


#define ONE     +1
#define TWENTY  +20
#define HUNDRED +100
 
// Here's a little example
#include <iostream>
 
int main()
{
    int x = ONE;
    std::cout << x << std::endl;
 
    x = ONE HUNDRED;
    std::cout << x << std::endl;
 
    x = ONE HUNDRED TWENTY;
    std::cout << x << std::endl;
 
    x = ONE HUNDRED TWENTY ONE;
    std::cout << x << std::endl;
}

Or even worse:


 
#define ONE     +0x001
#define TWENTY  +0x020
#define HUNDRED +0x100
Trienco
Trienco

Still trying to figure out the reasoning behind that. Is that what happens when your code analysis tool complains about "magic numbers" and somebody just decides to "fix it"?

Because having one such tool complain about '0' being a "magic number" really made me question the worth of that tool and what the creators' code would look like.

f@dzhttp://festini.device-zero.de
Bacterius
Bacterius


But they could have made it useful by adding pluses!


#define ONE     +1
#define TWENTY  +20
#define HUNDRED +100
 
// Here's a little example
#include <iostream>
 
int main()
{
    int x = ONE;
    std::cout << x << std::endl;
 
    x = ONE HUNDRED;
    std::cout << x << std::endl;
 
    x = ONE HUNDRED TWENTY;
    std::cout << x << std::endl;
 
    x = ONE HUNDRED TWENTY ONE;
    std::cout << x << std::endl;
}

Or even worse:


 
#define ONE     +0x001
#define TWENTY  +0x020
#define HUNDRED +0x100

Sadly this doesn't fully work:


TWO HUNDRED == 102

But don't worry - we can fix it! We just need to be "clever"...


#define AND +0
#define ONE +1
#define TWO +2
#define TWENTY +20
#define HUNDRED *100
 
// Here's a little example
#include <iostream>
 
int main()
{
    int x = TWO HUNDRED AND TWENTY ONE;
    std::cout << x << std::endl;
    // prints 221
}

This way you even get to write grammatically correct numbers. happy.png

“If I understand the standard right it is legal and safe to do this but the resulting value could be anything.”
Khatharr
Khatharr

I think we should pool our efforts and make a programming language where this kind of thing is sane.

void hurrrrrrrr() {__asm sub [ebp+4],5;}

There are ten kinds of people in this world: those who understand binary and those who don't.

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