map function

any ideas why negative values out of this:

code: [select]

long a;
long b;

void loop() {
 while(true){
   delay(1000);
   for (int = 0; < 255; i++){
       a = pow(i,3);
       b = map(a, 0,pow(255,3), 0,300 );
...
...
...
i print b on lcd. starts run nocely after 127 turns negative , starts run closer 0.

regards
orbitrek

it's somewhere in implementation of de map() function, integer overflow occuring. if don't need negative numbers being fed map(), might want use adapted method:

code: [select]

unsigned long mymap(unsigned long x, unsigned long in_min, unsigned long in_max, unsigned long out_min, unsigned long out_max) {

     return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

i think solve problem.

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