array traversal

[Tyler Knott]

arun wrote:
> i want to know during array traversal ,whether pointers do a better job than indices by considering the code snippet
> 
> int [10]array;
> foreach( value;array) {
>    //something
> }
> 
> i heard that implementations decides which one to use.i want to know how those two traversal differs? 
> 
> 
At least on x86/x64 they shouldn't differ.  They should both compile down to the pseudo-code x86 instruction

mov value,[array.ptr+sizeof(int)*index]

which is read as "move the value at the address (array.ptr+size(int)*index) into value" using flat pointer arithmetic 
(i.e. not C-style; use 1-byte increments always, even for types where sizeof(type) > 1 byte).  The above examples uses a 
bit of pseudo-code.  The real version uses a few more instructions to make sure that index is within array's bounds (in 
debug mode) and temporarily store array.ptr and index in a CPU registers.