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Diffstat (limited to 'source/arduino/float.rst')
| -rw-r--r-- | source/arduino/float.rst | 85 |
1 files changed, 26 insertions, 59 deletions
diff --git a/source/arduino/float.rst b/source/arduino/float.rst index 2f83a67..683f32d 100644 --- a/source/arduino/float.rst +++ b/source/arduino/float.rst @@ -1,88 +1,55 @@ +.. highlight:: cpp + .. _arduino-float: float ===== +.. TODO move all the useful examples over to arduino/double.rst. We +.. want to discourage using floats, since most of the common cmath +.. functions are only declared with doubles. + Description ----------- -Datatype for floating-point numbers, a number that has a decimal -point. Floating-point numbers are often used to approximate analog -and continuous values because they have greater resolution than -integers. Floating-point numbers can be as large as 3.4028235E+38 -and as low as -3.4028235E+38. They are stored as 32 bits (4 bytes) -of information. - - - -Floats have only 6-7 decimal digits of precision. That means the -total number of digits, not the number to the right of the decimal -point. Unlike other platforms, where you can get more precision by -using a double (e.g. up to 15 digits), on the Arduino, double is -the same size as float. - - +Single-precision floating point number. ``float`` values can be as +large as 3.4028235E+38 and as low as -3.4028235E+38. They are stored +as 32 bits (4 bytes) of information. -Floating point numbers are not exact, and may yield strange results -when compared. For example ``6.0 / 3.0`` may not equal ``2.0``. You -should instead check that the absolute value of the difference -between the numbers is less than some small number. +``float``\ s have only 6-7 decimal digits of precision. That means the total +number of digits, not the number to the right of the decimal point. +You can get more precision by using a :ref:`double <arduino-double>` +(which has a precision of about 16 decimal digits). - - -Floating point math is also much slower than integer math in -performing calculations, so should be avoided if, for example, a -loop has to run at top speed for a critical timing function. -Programmers often go to some lengths to convert floating point -calculations to integer math to increase speed. - - - -Examples --------- - -:: +The following example declares a ``float`` value named ``myfloat``:: float myfloat; - float sensorCalbrate = 1.117; - +This example declares a ``float`` value named ``sensorCalibrate``, +with value 1.117:: -Syntax ------- + float sensorCalibrate = 1.117; -:: +The general syntax for declaring a float named ``var`` with value +``val`` is:: float var = val; - - - -- var - your float variable name -- val - the value you assign to that variable - - - -Example Code ------------- - -:: +Here is a more extended example involving a :ref:`float cast +<arduino-floatcast>`:: int x; int y; float z; x = 1; - y = x / 2; // y now contains 0, ints can't hold fractions - z = (float)x / 2.0; // z now contains .5 (you have to use 2.0, not 2) - - + y = x / 2; // y now contains 0, ints can't hold fractions + z = float(x) / 2; // z now contains .5 See Also -------- - -- `int <http://arduino.cc/en/Reference/Int>`_ -- `double <http://arduino.cc/en/Reference/Double>`_ -- `Variable Declaration <http://arduino.cc/en/Reference/VariableDeclaration>`_ +- :ref:`int <arduino-int>` +- :ref:`double <arduino-double>` +- :ref:`Variables <arduino-variables>` |