Why Not Local Loops? Reasons Explained

[Svein]

strcpy is sort of like this, but with one very big difference. destination=source won't copy the character, it'l copy the pointer (*destination = *source) does a copy, notice that you must dereference the pointer and like I said destination++ has no pointer.

I absolutely agree. My only excuse is that I was late to an appointment and a bug snuck in (never write code in a hurry). Here are the correct statements:

char *destination, *source;

while (*destination++ = *source++);
...
while (*++destination= *source++);
...
while (*destination++ = *++source);
...
while (*++destination= *++source);
...

 

[jk22]

I never understood this, does ++source jump 4 bytes since it is an address ?

 

[Mark44]

I never understood this, does ++source jump 4 bytes since it is an address ?

"Pointer arithmetic is scaled by the type of object pointed to."
What this means is that you can't know what incrementing, decrementing, adding an integer to, subtracting an integer from, or subtracting two pointers will do, unless you know what type they are pointers to.

If source is declared as char * source;
then incrementing source evaluates to the address in memory of the next character.

If source is declared as int * source;
then incrementing source evaluates to the address in memory of the next int, which would typically be four bytes higher in memory.

If source is declared as double * source;
then incrementing source evaluates to the address in memory of the next double, which would typically be eight bytes higher in memory.

 

[Svein]

I never understood this, does ++source jump 4 bytes since it is an address ?

No. It depends on what the pointer points to. Thus:

char *cptr;
cptr++; /* Increases the pointer by 1, since it points to (an array of) characters */

short *sptr;
sptr++; /* Increases the pointer by 2, since it points to (an array of) shorts (16 bit) */

long *lptr;
lptr++; /* Increases the pointer by 4, since it points to (an array of) longs (32 bit) */

struct complicated *comptr;
comptr++; /* Increases the pointer by [I]sizeof(struct complicated[/I]), since it points to (an array of) structs */

But beware:

void *ptr;
ptr++;  /* Illegal, causes a compiler error. A void pointer is just a pointer, it cannot be used for anything but as a parameter in a call */

long *lptr;
lptr = ptr; /* Legal, since the void pointer is compatible with all pointers */
lptr++;  /* Now we know how to increment the pointer */