ldexp()
[Math]
double ldexp(double x, int exponent);Description
Returns the value of x times 2 raised to the power of exponent.
Parameters
x: The value to calculate the fractional part.
exponent: The power of 2 to multiply x.
Returns
The value of x times 2 raised to the power of exponent.
Example Code
The code reads the value of two potentiometers connected to pins
INX and INY and place the value of x
times 2 raised to the power of exponent on pin
OUT.
void setup() {
pinLabel(0, "INY"); // set the label of pin 0 to "INY"
pinLabel(1, "INX"); // set the label of pin 1 to "INX"
pinLabel(2, "OUT"); // set the label of pin 2 to "OUT"
pinMode(2, OUTPUT); // set pin 2 as output
pinLabel(3, "OUT2"); // set the label of pin 3 to "OUT2"
pinMode(3, OUTPUT); // set pin 3 as output
pinLabel(4, "VCC"); // set the label of pin 4 to "VCC"
powerPin(4); // set pin 4 as power pin
pinLabel(5, "GND"); // set the label of pin 5 to "GND"
groundPin(5); // set pin 5 as ground pin
}
void loop() {
// read the value of the potentiometers
int val_x = analogRead(0);
int val_y = analogRead(1);
// map the value of the potentiometers from 0 to 1023
// to the range of 0 to 10
double x = map(val_x, 0, 1023, 0, 10);
double y = map(val_y, 0, 1023, 0, 10);
// calculate the value of x times 2 raised to the power of y
double z = ldexp(x, (int) y);
// map the value of z from 0 to 10230 to 0 to 1023
int pwm = (int) map(z, 0, 10230, 0, 1023);
// write the value of pwm to pin 2
analogWrite(2, pwm);
}Notes and Warnings
This function permits a zero pointer as a directive to skip storing the exponent.
