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author | Marti Bolivar <mbolivar@mit.edu> | 2010-10-20 06:46:52 -0400 |
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committer | Marti Bolivar <mbolivar@mit.edu> | 2010-10-20 06:46:52 -0400 |
commit | 85c1c72db022bba891868afd3375e39dbe245701 (patch) | |
tree | 9d86a3db825667362a8c89a98a205586015aec94 /source/arduino/float.rst | |
parent | abcfcc62cc62dfc088d30d5a6b6c36d6c89f7b07 (diff) | |
download | librambutan-85c1c72db022bba891868afd3375e39dbe245701.tar.gz librambutan-85c1c72db022bba891868afd3375e39dbe245701.zip |
initial check-in of arduino docs in RST format (converted using wget+pandoc)
Diffstat (limited to 'source/arduino/float.rst')
-rw-r--r-- | source/arduino/float.rst | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/source/arduino/float.rst b/source/arduino/float.rst new file mode 100644 index 0000000..2f83a67 --- /dev/null +++ b/source/arduino/float.rst @@ -0,0 +1,88 @@ +.. _arduino-float: + +float +===== + +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. + + + +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. + + + +Examples +-------- + +:: + + float myfloat; + float sensorCalbrate = 1.117; + + + +Syntax +------ + +:: + + float var = val; + + + + +- var - your float variable name +- val - the value you assign to that variable + + + +Example Code +------------ + +:: + + 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) + + + +See Also +-------- + + +- `int <http://arduino.cc/en/Reference/Int>`_ +- `double <http://arduino.cc/en/Reference/Double>`_ +- `Variable Declaration <http://arduino.cc/en/Reference/VariableDeclaration>`_ + |