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static
Descrição
A palavra-chave static é usada para criar variáveis que são visíveis para apenas uma função. No entanto, diferentemente de variáveis locais, que são criadas e destruidas toda vez que uma função é chamada, variáveis static persistem entre chamadas da função, preservando seu valor.
Variáveis declaradas como static são criadas e inicializadas apenas a primeria vez que uma função é chamada.
Código de Exemplo
/* RandomWalk
Paul Badger 2007
RandomWalk wanders up and down randomly between two
endpoints. The maximum move in one loop is governed by
the parameter "stepsize".
A static variable is moved up and down a random amount.
This technique is also known as "pink noise" and "drunken walk".
*/
#define randomWalkLowRange -20
#define randomWalkHighRange 20
int stepsize;
int thisTime;
int total;
void setup() {
Serial.begin(9600);
}
void loop() {
// test randomWalk function
stepsize = 5;
thisTime = randomWalk(stepsize);
Serial.println(thisTime);
delay(10);
}
int randomWalk(int moveSize) {
static int place; // variable to store value in random walk - declared static so that it stores
// values in between function calls, but no other functions can change its value
place = place + (random(-moveSize, moveSize + 1));
if (place < randomWalkLowRange) { // check lower and upper limits
place = randomWalkLowRange + (randomWalkLowRange - place); // reflect number back in positive direction
}
else if (place > randomWalkHighRange) {
place = randomWalkHighRange - (place - randomWalkHighRange); // reflect number back in negative direction
}
return place;
}
Ver também
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