What's your philosophy?

http://developeronline.blogspot.com/2009/04/if-philosophers-were-programmers.html

Modulo a negative number

I'm quite surprised to found that MOD with -ve dividend number is NOT THE SAME as MOD with +ve dividend number.

What is modulo (MOD)?
It's a operation/function which returns the remainder of a division by two integers. It's like division, except it returns the remainder. E.g. 9/4=2.25, 9 MOD 4 = 1 (since 2x4+1=9).

For +ve dividend number, x MOD n means = x - (floor(x/n) * n)
But for -ve dividend number, x MOD n means =

1. x + ( floor(-x/n)+1 ) * n, or
2. -(-x MOD n) + n

Literally, the solution is like this : do as normal MOD, but add the remainder (negative number) with the divisor. E.g. -8 MOD 3, frankly return -2, but then add -2 with 3 = 1. Also in the above formulae, floor() is a function which return the answer rounded up towards bottom integer value e.g. 8.4 = 8, 11.9 = 11 etc. (always take the low integer).

Example:

x = 11, n = 3

11 MOD 3, use x - (floor(x/n) * n);
= 11 - ( floor(11/3) * 3)
= 11 - (3 * 3)
= 2

but if x = -11, n = 3

-11 MOD 3, use x + ( floor(-x/n)+1 ) * n;
= -11 + ( floor(11/3) + 1) * 3
= -11 + (3 + 1) * 3
= -11 + 12
= 1

or

-11 MOD 3, use -(-x MOD n) + n
= -(-(-11) MOD 3) + 3
= -(11 MOD 3) + 3
= -2 + 3
= 1

but, what if -11 MOD -3?
Hmmm...

Links:
http://en.wikipedia.org/wiki/Modulo_operation


p/s: if u still wondering what is 'dividend' : if a/b = c, a is dividend, b is divisor and c is quotient.

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A blunder ... can compiler help?

Yesterday, as i was writing another code, i made this simple mistake, illustrated by the following example (example only, don't do this!):

int foo(int i)
{

int j = 2;
if(i > 0)
return i; /* here should be j*/
else
return 0;

}

ok, this is not a good example (it is rubbish), yet clarify my point. It is not simply a typo (which can possibly be another blunder, duh!). I wrote 'return i' instead of 'return j' because i thought it should be 'i'. This is called semantical error. It is not syntactical error, nor grammatical error. It is simply a blunder, and worse, it can't be detected by a compiler.

Is it only about logic?

What programming is all about? I mean the philosophy beneath. Is it only about logical thinking, or pure imagination (creative) or something that combined both? Hmmm... i'm still curious ...

However, i believe that both thinking are involved (other than the fact both are the functions of our brain). Since at certain levels, we have to use our abstract, creative imagination as to think about a any possible solutions. Whereas during the level where we are going to form the solution, we must use our logical thinking.

... ?