From 5a7dd1bea32458a4afc038984a903959134b82d3 Mon Sep 17 00:00:00 2001
From: Hanna Mendes Levitin <hanna@anomaly-3.local>
Date: Wed, 1 Dec 2010 03:37:07 -0600
Subject: docs, now with style

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 source/lang/cpp/if.rst | 121 +++++++++++++++++++++++++++++++++++++++++++++++++
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+.. highlight:: cpp
+
+.. _lang-if:
+
+``if``/``else``
+===============
+
+An ``if`` statement is used to execute code when certain conditions
+are met.  The general syntax for an ``if`` statement is::
+
+    if (condition) {
+        body
+    }
+
+An ``if`` statement first tests whether its *condition* is true (such
+as an input being above a certain number).  If the condition is true,
+the ``if`` statement executes its *body*, which is made up of lines of
+code inside :ref:`curly braces <lang-curly-braces>`.  If the condition
+is false, the body is not executed.  Here's a more concrete example::
+
+    if (someVariable > 50) {
+      // do something here
+    }
+
+The program tests to see if ``someVariable`` is greater than 50. If it
+is, the program executes every line in the curly braces (which in the
+above example does nothing, since the body is just the :ref:`comment
+<lang-comments>` line "``// do something here``").
+
+Put another way, if the statement in parentheses is true, the
+statements inside the braces are run. If not, the program skips over
+the code.
+
+An ``if`` statement's condition (which is inside the parentheses after
+``if``) often uses one or more :ref:`boolean <lang-boolean>` or
+:ref:`comparison <lang-comparison>` operators.
+
+Writing the if Body
+-------------------
+
+The brackets may be omitted after an ``if`` statement's
+conditional. If this is done, the next line (which ends in a
+semicolon) becomes the only line in the body.  The following three
+``if`` statements all do the same thing::
+
+    if (x > 120) digitalWrite(ledPin, HIGH);
+
+    if (x > 120)
+        digitalWrite(ledPin, HIGH);
+
+    if (x > 120) {
+        digitalWrite(ledPin, HIGH);
+    }
+
+However, the following two examples are different::
+
+    // example 1: two lines of code in the if body
+    if (x > 120) {
+      digitalWrite(ledPin1, HIGH);
+      digitalWrite(ledPin2, HIGH);
+    }
+
+    // example 2: one line of code in the if body, and
+    // another line of code after the if statement
+    if (x > 120)
+      digitalWrite(ledPin1, HIGH); // this is in the if body
+      digitalWrite(ledPin2, HIGH); // this is NOT in the if body
+
+In the first example, since the body is enclosed in curly braces, both
+lines are included.  In the second example, since the curly braces are
+missing, only the first line is in the ``if`` body.
+
+``else``
+--------
+
+``if``/\ ``else`` allows greater control over the flow of code than
+the basic :ref:`if <lang-if>` statement, by allowing multiple tests to
+be grouped together. For example, an :ref:`analog input
+<lang-analogread>` could be tested, with one action taken if the input
+was less than 500, and another action taken if the input was 500 or
+greater. The code would look like this::
+
+    if (pinFiveInput < 500) {
+      // action A
+    } else {
+      // action B
+    }
+
+``else`` can precede another ``if`` test, so that multiple, mutually
+exclusive tests can be run at the same time.
+
+Each test will proceed to the next one until a true test is
+encountered. When a true test is found, its associated block of code
+is run, and the program then skips to the line following the entire
+if/else construction. If no test proves to be true, the default
+``else`` block is executed, if one is present, and sets the default
+behavior.
+
+Note that an ``else if`` block may be used with or without a
+terminating ``else`` block, and vice-versa. An unlimited number of
+such ``else if`` branches is allowed.  Here is a code example::
+
+    if (pinFiveInput < 500) {
+      // do Thing A
+    } else if (pinFiveInput >= 1000) {
+      // do Thing B
+    } else {
+      // do Thing C
+    }
+
+Another way to express branching, mutually exclusive tests, is with a
+:ref:`switch/case <lang-switchcase>` statement.
+
+
+See Also
+--------
+
+- :ref:`boolean operators <lang-boolean>`
+- :ref:`comparison operators <lang-comparison>`
+
+.. include:: cc-attribution.txt
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