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Diffstat (limited to 'source/arduino/double.rst')
| -rw-r--r-- | source/arduino/double.rst | 36 |
1 files changed, 25 insertions, 11 deletions
diff --git a/source/arduino/double.rst b/source/arduino/double.rst index 4e7f20c..658af12 100644 --- a/source/arduino/double.rst +++ b/source/arduino/double.rst @@ -3,30 +3,44 @@ double ====== -Desciption ----------- +Description +----------- -Double precision floating point number. Occupies 4 bytes. +Double precision floating point number. Occupies 8 bytes. +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. +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. -The double implementation on the Arduino is currently exactly the -same as the float, with no gain in precision. +For more information about floating point math, see the `Wikipedia +article <http://en.wikipedia.org/wiki/Floating_point>`_\ . +Floating-point numbers represent numbers with "decimal point", unlike +integral types, which always represent whole numbers. Floating-point +numbers are often used to approximate analog and continuous values +because they have greater resolution than integers. +The double implementation on the Maple uses twice the number of bytes +as a :ref:`float <arduino-float>`, with the corresponding gains in +precision. Tip --- Users who borrow code from other sources that includes double variables may wish to examine the code to see if the implied -precision is different from that actually achieved on the Arduino. +precision is different from that actually achieved on the Maple. +See Also +-------- -See: ----- - - -- `float <http://arduino.cc/en/Reference/Float>`_ +- :ref:`float <arduino-float>` |