GP32 Increase Variable

[pea]

Hey all,

Have temporary brain-fry problems
You know how
length++;
increases value of var 'length' by one?

What is the shorthand to increase the value pointed to by a pointer-to-an-int?
Basically the shorthand for this:

int *length;
*length = (*length)+1;

Because
*length++

Is very dangerous and incorrect (basically, return the value pointed to by length - which is ignored - and then increase the pointer by 1)

 

[Drag]

length++;

I think. I'm not 100% positive.

 

[pea]

No, that would just increase the pointer to point at the next int in memory

 

[WhiteFalcon]

*length = (*length) + 1;

is okay as is

*length = *length + 1;

but never

*length++;

 

[iignotus]

::bows::

 

[Squidge]

To increase the int pointed to by length quickly, you could do:

(*length)++;

or treat it as an array, which is safer and more readable:

length[0]++;

Which is also my preferred method.

 

[gp32rich]

If you're going for shorthanded elegance, this ...

#include <stdio.h>

void main(void)
{
	int a[5]={1,8,7,3,6},*l=a;

	printf("%d",*l);

	(*l)+=1;

	printf("%d",*l);

	(*l)++;

	printf("%d",*l);

	*l+=1;

	printf("%d",*l);

	*l++;

	printf("%d",*l);
}

gives...

12348

Use anything but *l++

 

[janniz]

...

Use anything but *l++

​

Don't forget

 ++*l;

as a valid choice

Janniz

 

[pea]

Thanks all. Brackets huh

Janniz

++*l;

is NOT a valid choice! It would increase the pointer and then return the value. You may be thinking of

++(*l);

 

[K-teto]

To increase the int pointed to by length quickly, you could do:

(*length)++;

or treat it as an array, which is safer and more readable:

length[0]++;

Which is also my preferred method.

​

and mine, this way is much more clear to me (i'm too lazy to comment everything)

 

[janniz]

++*l;

is NOT a valid choice! It would increase the pointer and then return the value. You may be thinking of

++(*l);

​

I don't have K&R with me now but I'm pretty sure that ++*l would do the job...

Pointer dereference and ++ have are both unary operator... so they will have the same priority and will be evaluated from right to left...
++*l is the same as ++(*l) and WRONG *l++ is the same as *(l++)...

I compiled&run this piece of code on gcc 3.3.3 under cygwin:

#include <stdio.h>

void main(void)
{
int a[5]={1,8,7,3,6},*l=a;

printf("%d",*l);

(*l)+=1;

printf("%d",*l);

(*l)++;

printf("%d",*l);

*l+=1;

printf("%d",*l);

++*l;

printf("%d",*l);

*l++;

printf("%d",*l);
}

and the output was:
123458

See ya
Janniz

 

[gp32rich]

Don't forget

 ++*l;

as a valid choice

Hmm. Yeah. I forget about prefixing the increment.
But then again, I hardly ever* use it.



My preferred method of non-inline increment (ie. standalone statement) is v+=1;
v++; on it's own looks kinda nasty to me




* never say never