Arduino入門：算術関数

//Arduino Sketch Example: min(x, y)
//Date: 2015.1.18
//Edited and Modified by: easy labo
//Original Source: Arduino Reference (http://arduino.cc/en/Reference/HomePage)

//Syntax
min(x, y)

//Parameters
//x: the first number, any data type
//y: the second number, any data type

//Returns
//The smaller of the two numbers.

//Description
//Calculates the minimum of two numbers.

//Examples
sensVal = min(sensVal, 100); // assigns sensVal to the smaller of sensVal or 100
                             // ensuring that it never gets above 100.

//Note
/*
Perhaps counter-intuitively, max() is often used to constrain the lower end of a variable's range, while min() is used to constrain the upper end of the range.
*/

//Warning
/*
Because of the way the min() function is implemented, avoid using other functions inside the brackets, it may lead to incorrect results
*/

//Arduino Sketch Example: max(x, y)
//Date: 2015.1.18
//Edited and Modified by: easy labo
//Original Source: Arduino Reference (http://arduino.cc/en/Reference/HomePage)

//Syntax
max(x, y)

//Parameters
//x: the first number, any data type
//y: the second number, any data type

//Returns
//The larger of the two parameter values.

//Description
//Calculates the maximum of two numbers.

//Example
sensVal = max(senVal, 20); // assigns sensVal to the larger of sensVal or 20
                           // (effectively ensuring that it is at least 20)

//Note
/*
Perhaps counter-intuitively, max() is often used to constrain the lower end of a variable's range, while min() is used to constrain the upper end of the range.
*/

//Warning
/*
Because of the way the max() function is implemented, avoid using other functions inside the brackets, it may lead to incorrect results
*/

max(a--, 0);   // avoid this - yields incorrect results

a--;           // use this instead -
max(a, 0);     // keep other math outside the function

//Arduino Sketch Example: abs(x)
//Date: 2015.1.18
//Edited and Modified by: easy labo
//Original Source: Arduino Reference (http://arduino.cc/en/Reference/HomePage)

//Syntax
abs(x)

//Parameters
//x: the number

//Returns
//x: if x is greater than or equal to 0.
//-x: if x is less than 0.

//Description
//Computes the absolute value of a number.

//Warning
/*
Because of the way the abs() function is implemented, avoid using other functions inside the brackets, it may lead to incorrect results.
*/

abs(a++);   // avoid this - yields incorrect results

a++;          // use this instead -
abs(a);       // keep other math outside the function

//Arduino Sketch Example: constrain(x, a, b)
//Date: 2015.1.18
//Edited and Modified by: easy labo
//Original Source: Arduino Reference (http://arduino.cc/en/Reference/HomePage)

//Syntax
constrain(x, a, b)

//Parameters
//x: the number to constrain, all data types
//a: the lower end of the range, all data types
//b: the upper end of the range, all data types

//Returns
//x: if x is between a and b
//a: if x is less than a
//b: if x is greater than b

//Description
//Constrains a number to be within a range.

//Example
sensVal = constrain(sensVal, 10, 150);

// limits range of sensor values to between 10 and 150 

//Arduino Sketch Example: map
//Date: 2015.1.18
//Edited and Modified by: easy labo
//Original Source: Arduino Reference (http://arduino.cc/en/Reference/HomePage)

long map(long value, long fromLow, long fromHigh, long toLow, long toHigh) {
  return (value - fromLow) * (toHigh - toLow) / (fromHigh - fromLow) + toLow;
}

//Arduino Sketch Example: Syntax of map
//Date: 2015.1.18
//Edited and Modified by: easy labo
//Original Source: Arduino Reference (http://arduino.cc/en/Reference/HomePage)

//Syntax
 map(value, fromLow, fromHigh, toLow, toHigh)

//Parameters
//value: the number to map
//fromLow: the lower bound of the value's current range
//fromHigh: the upper bound of the value's current range
//toLow: the lower bound of the value's target range
//toHigh: the upper bound of the value's target range

//Returns
//The mapped value.

//Arduino Sketch Example: map example 1
//Date: 2015.1.18
//Edited and Modified by: easy labo
//Original Source: Arduino Reference (http://arduino.cc/en/Reference/HomePage)

//Description
/*
Re-maps a number from one range to another. That is, a value of fromLow would get mapped to toLow, a value of fromHigh to toHigh, values in-between to values in-between, etc.
Does not constrain values to within the range, because out-of-range values are sometimes intended and useful. The constrain() function may be used either before or after this function, if limits to the ranges are desired.
Note that the "lower bounds" of either range may be larger or smaller than the "upper bounds" so the map() function may be used to reverse a range of numbers, for example
*/

y = map(x, 1, 50, 50, 1);

//The function also handles negative numbers well, so that this example

y = map(x, 1, 50, 50, -100);

/*
is also valid and works well.
The map() function uses integer math so will not generate fractions, when the math might indicate that it should do so. Fractional remainders are truncated, and are not rounded or averaged.
*/

//Arduino Sketch Example: map example 2
//Date: 2015.1.18
//Edited and Modified by: easy labo
//Original Source: Arduino Reference (http://arduino.cc/en/Reference/HomePage)

//Example
//Map an analog value to 8 bits (0 to 255)
void setup() {}

void loop()
{
  int val = analogRead(0);
  val = map(val, 0, 1023, 0, 255);
  analogWrite(9, val);
}

//Arduino Sketch Example: pow
//Date: 2015.1.18
//Edited and Modified by: easy labo
//Original Source: Arduino Reference (http://arduino.cc/en/Reference/HomePage)

//Syntax
pow(base, exponent)

//Parameters
//base: the number (float)
//exponent: the power to which the base is raised (float)

//Returns
//The result of the exponentiation (double)

//Description
/*
Calculates the value of a number raised to a power. Pow() can be used to raise a number to a fractional power. This is useful for generating exponential mapping of values or curves.
*/

//Example
a = pow(10, 1.5); // return around 31

//Arduino Sketch Example: sqrt
//Date: 2015.1.18
//Edited and Modified by: easy labo
//Original Source: Arduino Reference (http://arduino.cc/en/Reference/HomePage)

//Syntax
sqrt(x)

//Parameters
//x: the number, any data type

//Returns
//double, the number's square root.

//Description
//Calculates the square root of a number.