From d9cbd78e29d42e70bb46641dd43ee0772c8c975f Mon Sep 17 00:00:00 2001
From: Marti Bolivar <mbolivar@mit.edu>
Date: Sun, 28 Nov 2010 11:23:33 -0500
Subject: reorganized all the arduino/ docs into a lang/ subdirectory since
 they're properly CC attributed now.

---
 source/lang/switchcase.rst | 117 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 117 insertions(+)
 create mode 100644 source/lang/switchcase.rst

(limited to 'source/lang/switchcase.rst')

diff --git a/source/lang/switchcase.rst b/source/lang/switchcase.rst
new file mode 100644
index 0000000..46c47d8
--- /dev/null
+++ b/source/lang/switchcase.rst
@@ -0,0 +1,117 @@
+.. highlight:: cpp
+
+.. _lang-switchcase:
+
+switch / case statements
+========================
+
+Like :ref:`if/else <lang-else>` blocks, A ``switch`` statement
+controls program flow by allowing you to specify different code that
+should be executed under various cases.
+
+The general syntax looks like this::
+
+    switch (var) {
+    case val1:
+        // statements
+        break;
+    case val2:
+        // statements
+        break;
+    ...
+    default:
+        // statements
+    }
+
+Where ``var`` is a variable whose value to investigate, and the
+``val1``, ``val2`` after each ``case`` are constant values that
+``var`` might be.
+
+
+Description
+-----------
+
+A ``switch`` statement compares the value of a variable to the values
+specified in ``case`` statements. When a ``case`` statement is found
+whose value matches that of the variable, the code in that case
+statement is run.
+
+Here's a more concrete example::
+
+      switch (var) {
+      case 1:
+          doThing1();
+          break;
+      case 2:
+          doThing2();
+          break;
+      }
+      afterTheSwitch();
+
+In the above example, if ``var == 1``, then the code beginning on the
+line after ``case 1`` gets executed.  That is, if ``var`` is one,
+``doThing1()`` gets called first, and then the ``break`` statement is
+executed.
+
+The ``break`` keyword exits the ``switch`` statement, and is typically
+used at the end of each ``case``.  Since there is a ``break`` at the
+end of ``case 1``, the ``switch`` statement exits, and the next line
+to be run is the one which calls ``afterTheSwitch()``.
+
+Without a ``break``, the ``switch`` statement will continue executing
+the following ``case`` expressions ("falling-through") until a
+``break`` (or the end of the switch statement) is reached.  Let's
+pretend the ``switch`` looked like this instead::
+
+      switch (var) {
+      case 1:
+          doThing1();
+          // no break statement anymore
+      case 2:
+          doThing2();
+          break;
+      }
+      afterTheSwitch();
+
+Now, if ``var`` is one, ``doThing1()`` gets executed like before.
+However, without a ``break``, the code would continue to be executed
+line-by-line, so ``doThing2()`` would be called next.  At this point,
+a ``break`` has been reached, so the program continues by calling
+``afterTheSwitch()``.  This is usually not what you want, which is why
+each ``case`` usually has a ``break`` at the end.
+
+Writing "``default:``" instead of a ``case`` statement allows you to
+specify what to do if none of the ``case`` statements matches.  Having
+a ``default`` is optional (you can leave it out), but if you have one,
+it must appear after all of the ``case`` statements.  Let's add a
+``default`` to the ``switch`` we've been discussing::
+
+      switch (var) {
+      case 1:
+          doThing1();
+          break;
+      case 2:
+          doThing2();
+          break;
+      default:
+          doSomethingElse();
+      }
+      afterTheSwitch();
+
+If ``var`` is one, then ``doThing1()`` gets called.  If ``var`` is
+two, ``doThing2()`` gets called.  If ``var`` is anything else,
+``doSomethingElse()`` gets called.  As stated above, a ``default`` is
+optional.  If you're missing one and none of the ``case`` statements
+match, the ``switch`` does nothing at all, as if it weren't there.
+
+``switch`` statements are often used with an ``enum`` value as the
+variable to compare.  In this case, you can write down all of the
+values the ``enum`` takes as ``case`` statements, and be sure you've
+covered all the possibilities.
+
+See also:
+---------
+
+- :ref:`if...else <lang-else>`
+
+.. include:: cc-attribution.txt
-- 
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