help

[Richard Heathfield]

Bart C said:

Dangling else problem, you mean?

No, the use of +

 

[Bart C]

Bart C said:


No, the use of +

omg! Didn't see that. Result of tidying up.

Better use return ++d then

Bart

 

[spaglia]

Hi,

Can anyone please give me a hint/logic to divide a number with any
number without using '/' '+' '*' '-'.

Thank You.

Regards,
New

I think this will do it. It handles unsigned operands and /0 is not
special cased (assumes 32-bit integers):

typedef struct {unsigned quot; unsigned rem;} udiv_t;
udiv_t udiv(unsigned divdnd, unsigned divisor)
{
udiv_t res;

unsigned rem = 0;
unsigned bits = 32;
do {
// shift dividend left into remainder
rem = (rem << 1) | (divdnd >> 31);
divdnd <<= 1;

// if ramainder larger than divisor then
// correct and add 1 to dividend
if (rem >= divisor)
{
// rem -= divisor
unsigned cnt = divisor;
while (cnt--) rem--;
divdnd |= 1;
}
}
while (--bits);

res.quot = divdnd;
res.rem = rem;

return res;
}

-Steve

 

[CBFalconer]

I think this will do it. It handles unsigned operands and /0 is
not special cased (assumes 32-bit integers):

The use of "--" or "++" involves the use of '-' or '+'. At any
rate, why spend time on such a foolish project?

 

[spaglia]

The use of "--" or "++" involves the use of '-' or '+'.  At any
rate, why spend time on such a foolish project?

Right, and comparisons are really subtractions and a logical or is
really addition without carry, etc.

I'm guessing this is a school project of some kind.

Steve

 

[Bart C]

The use of "--" or "++" involves the use of '-' or '+'.

'+' could mean the character +, or the operator symbol +, the latter seems
more logical; the OP hasn't clarified. (And disallowing the '*' character
would make comments difficult.)

And whether ++ may or not involve + at some implementation level is
irrelevant; otherwise the entire exercise done correctly could implement the
divide / operator and therefore would be disqualified!

At any rate, why spend time on such a foolish project?

In my case (newish to C) it's a useful exercise.

 

[Army1987]

Hi,

Can anyone please give me a hint/logic to divide a number with any
number without using '/' '+' '*' '-'.

For integers:
#include <stdlib.h>
....
int result;
div_t q;
q = div(numer, denom);
result = q.quot;

For floating point (C99 only):
#include <math.h>
#include <limits.h>
result = fma(numer, pow(denom, copysign(1, cos(3)), 0);

 

[Army1987]

Here are some other ways to divide without using division that are
equally horrible:

#include <stdio.h>
#include <math.h>
#include <float.h>

int double_compare(double d1, double d2)
{
if (d1 > d2)
if ((d1 - d2) < fabs(d1 * DBL_EPSILON))

You can't use - or *, either.

 

[Army1987]

For integers:
#include <stdlib.h>
...
int result;
div_t q;
q = div(numer, denom);
result = q.quot;

For floating point (C99 only):
#include <math.h>
#include <limits.h>
result = fma(numer, pow(denom, copysign(1, cos(3)), 0);

or even... copysign(1, EOF)
, (provided <stdio.h> has been #included) of course...

 

[Chris Dollin]

Bart C wrote:

In my case (newish to C) it's a useful exercise.

I think there are /many/ other things about C that would
make more useful initial exercises than re-implementing
arithmetic.

Do you not?

 

[Bart C]

I think there are /many/ other things about C that would
make more useful initial exercises than re-implementing
arithmetic.

Do you not?

Maybe. The OPs tutor (if s/he exists) seemed to think there was a use. Does
it matter? The learning is the important thing. And the limitation imposed
gave an added dimension. And posting code on c.l.c so that it could possibly
be savaged to pieces was an extra kick.

Bart