merge libmaple docs ("leaflabs-docs") into ./docs

In the past, libample documentation was forked out of this repository
because the documentation had increased in scope. For the librambutan,
and the rambutan project in general, we will try to keep documentation
closer to the source code, so the librambutan-specific documentation
should live here. Other sections of leaflabs-docs will be culled in a
following commit.

This merge attempts to maintain history by using a subtree strategy.
Followed directions at:

    http://nuclearsquid.com/writings/subtree-merging-and-you/

Full history for files should be accessible using the "--follow" flag to
git log, eg:

    git log --follow docs/source/adc.rst

It should be possible to pull patches from leaflabs-docs with:

    git pull -s subtree leaflabs-docs master

... at least until the docs in this repository diverge significantly.

1 files changed, 56 insertions, 0 deletions

diff --git a/docs/source/lang/cpp/static.rst b/docs/source/lang/cpp/static.rst
new file mode 100644
index 0000000..8c52ba0
--- /dev/null
+++ b/docs/source/lang/cpp/static.rst
@@ -0,0 +1,56 @@
+.. highlight:: cpp
+
+.. _lang-static:
+
+``static``
+==========
+
+The ``static`` keyword can be used to create variables that are
+visible to only one function. However, unlike local variables that get
+created and destroyed every time a function is called, ``static``
+variables persist beyond the function call, preserving their data
+between function calls.
+
+Variables declared as ``static`` will only be created and initialized
+the first time a function is called.
+
+.. note:: This is only one use of the ``static`` keyword in C++.  It
+   has some other important uses that are not documented here; consult
+   a reliable C++ reference for details.
+
+Example
+-------
+
+One use case for ``static`` variables is implementing counters that
+last longer than the functions which need them, but shouldn't be
+shared to other functions.  Here's an example::
+
+    void setup() {
+        SerialUSB.begin();
+    }
+
+    void loop() {
+        int reading;
+        if (timeToReadSensors()) {
+            reading = readSensors();
+        }
+        // do something with reading
+    }
+
+    int readSensors() {
+        static int numSensorReadings = 0;
+        numSensorReadings++;
+        if (numSensorReadings % 100 == 0) {
+            SerialUSB.print("just got to another 100 sensor readings");
+        }
+        return analogRead(...);
+    }
+
+In this example, the static variable ``numSensorReadings`` is
+initialized to zero the first time ``readSensors()`` is called, and
+then incremented, so it starts out at one.  Subsequent calls to
+``readSensors()`` won't reset ``numSensorReadings`` to zero, because
+it was declared ``static``.  Thus, ``numSensorReadings`` is a count of
+the number of times that ``readSensors()`` has been called.
+
+.. include:: /arduino-cc-attribution.txt