Thanks for Your answers!
On 23/09/07 14:14:33, candido lopez rodriguez wrote:
> switch statement: if the case is in sequence (for example case 1: 2, etc)
> the compiler will translate to a translation table (a very short operation)
> if not the compiler will use jumps (same as if/then else).
So a switch statement cannot be slower than an else-if?
>try to eliminate operations, for example
>
> if ( a == 1)
> b=10
> else
> b = 1
>
> change to
> b=1;
> if ( a == 1)
> b= 10;
>
>
> about your question where to change from an if to a switch
>
> if the compare is other than a int/char use if
I'm not sure what You mean here. Aren't all comparisions int/char (equal zero
or not)?
>
> does it save RAM when I define variables in the innermost scope possible?
> no try to reuse variables
Reuse is best sure, but what about:
void Openfile(void){
if (error){
char s[5];
itoa(int, s, 10);
lcd_write_str(s);
}
}
Is the char-array only allocated when the error occures, or will it be
allocated when the function is called, or is it already allocated when the
whole programme is loaded?
>
> - is it better to nest switch statement or use else-if instead of nesting?
> think about the logic, are the if needed to begin? the compiler needs to
generate jump operations, depending how far needs to go it needs to require a
long jump and for your question both will be the same
>
>
> - when does it help writing out loops?
>
> speed vs memory (you mean unroll loops)
Is there a method to let the preprocessor unroll loops?
> please do not do things like I see all the time
> int count;
> for(count=0; count < function(a); count++)
> {
> operations
> }
>
> instead
> int count;
> int limit = function(a);
> for (count=0; count < limit; count++)
> {
> operations;
> }
>
>
> - should I concider using banned goto instructions for microcontrollers?
>
> a good book that I highly recommend is hacker delight henry s. warren junior
> ISBN-0-201-91465-4
Great, I'll have a look into it. Thank You very much.
Lynx
