Page 59 - Programming the Photon Getting Started With the Internet of Things

anywhere within the whole program, this means you need to understand your program in
order to know what happened to the variable. Sometimes it is much easier to debug when
you only use that variable within its own scope.

Floats

All the examples that we have used thus far have included int variables. Integer variables
are by far the most commonly used type; however, there are others that you should be

familiar with.

One type that will become more relevant later on in this book is floats. A good
example is the conversion of temperature when using temperature sensors. The variable

type is a number that may consist of a decimal place for more precise measurements such
as 1.6. Take a look at the following formula:

f = c * 9 / 5 + 32

This formula is the calculation for converting temperature from degrees Celsius to degrees
Fahrenheit. If we give c the value of 23, then f will be 23 * 9 / 5 + 32 or 73.4. If we set f as
an integer, then the value will return 73.

Note the order in which the calculation is in. If we are not careful in the order in which
we calculate, things may turn out differently when using integers. For example, this
formula:

f = (c / 5) * 9 + 32

would result in the following:

23 is divided by 5, which returns 4.6, which is then rounded down to 4.

4 is then multiplied by 9 and 32 is added to give a result of 68, which is way off our
actual temperature value of 73.4.

For situations like this, we use floats; in the following example our temperature

conversion function is rewritten to use floats:

float centToFaren (float c)

{
float f = c * 9.0 / 5.0 + 32.0;
return f;
}

We have also added .0 to the end of each value—this way our compiler knows that it
should treat the values as floats and not integers.