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.. highlight:: cpp
.. _arduino-include:
#include
========
``#include`` is used to include outside libraries in your sketch.
This gives the programmer access to a large group of standard C
libraries (groups of pre-made functions and data types), and also
libraries written especially for Maple.
Example
-------
This example (from the `Arduino LiquidCrystal Tutorial
<http://arduino.cc/en/Tutorial/LiquidCrystal>`_) includes a library
that is used to control :ref:`LCD displays <liquid-crystal>`::
// include the library code:
#include <LiquidCrystal.h>
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
void setup() {
// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
// Print a message to the LCD.
lcd.print("hello, world!");
}
void loop() {
// set the cursor to column 0, line 1
// (note: line 1 is the second row, since counting begins with 0):
lcd.setCursor(0, 1);
// print the number of seconds since reset:
lcd.print(millis()/1000);
}
Note that a ``#include`` line, like :ref:`#define <arduino-define>`,
has **no semicolon**. The compiler will print strange error messages
if you add one.
C Standard Library
------------------
The standard C library that comes with Maple is called `newlib
<http://sourceware.org/newlib/>`_. Its main sources of documentation
are its `main reference <http://sourceware.org/newlib/libc.html>`_
page and its `math functions
<http://sourceware.org/newlib/libm.html>`_ reference page. Here's an
example that imports the math.h library in order to take the `cube
root <http://en.wikipedia.org/wiki/Cube_root>`_ of a number::
#include <math.h>
void setup() {
// no setup necessary
}
void loop() {
// "cbrt" stands for "cube root"
double cubeRootOf3 = cbrt(3.0);
// prints a number that is approximately the cube root of 3:
SerialUSB.println(cubeRootOf3);
}
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