From 210f3d2b1555bae87c9de27ea145e16d3bddb0f8 Mon Sep 17 00:00:00 2001 From: Marti Bolivar Date: Fri, 3 Dec 2010 20:18:00 -0500 Subject: cleaning up previous commits. note that addition of new files under docs/source/lang/api and docs/source/lang/cpp which were just copies of files in docs/source/lang/ imply that change history is lost to git. --- source/lang/scope.rst | 120 -------------------------------------------------- 1 file changed, 120 deletions(-) delete mode 100644 source/lang/scope.rst (limited to 'source/lang/scope.rst') diff --git a/source/lang/scope.rst b/source/lang/scope.rst deleted file mode 100644 index 7b65bab..0000000 --- a/source/lang/scope.rst +++ /dev/null @@ -1,120 +0,0 @@ -.. highlight:: cpp - -.. _lang-scope: - -Scope -===== - -Variables in the C++ programming language, which Maple uses (all of -your sketches are C++ programs in disguise), have a property called -*scope*. Simply put, a variable's scope is made up of all of the -lines where the variable can be used. - -Scope in C++ is a fairly complex topic, so we won't try to describe it -in full here. Instead, we present a simplified view, describing two -different kinds of scopes, *global* and *local*. For more detailed -information, consult a C++ reference. - -Global and Local Variables --------------------------- - -A global variable is one that can be "seen" by every function in a -program. In the :ref:`Maple IDE `, any variable declared outside -of a function (like :ref:`setup() ` and :ref:`loop() -`) is a global variable. - -A local variable can only be "seen" inside of a particular function. -You can declare a variable to be local to a function by declaring it -inside of the :ref:`curly braces ` which enclose -that function. - -When programs start to get larger and more complex, local variables -are a useful way to ensure that a function has exclusive access to its -own variables. This prevents programming errors when one function -mistakenly modifies variables used by another function. - -It is also sometimes useful to declare and initialize a variable -inside a :ref:`for ` loop. This creates a variable that -can only be accessed from inside the loop body. - -Example -------- - -Here is an example sketch (which you can copy into the Maple IDE and -run on your Maple) that illustrates the use of global and local -variables, as well as declaring variables inside of a ``for`` loop. -Be sure to open a :ref:`serial monitor ` after you -:ref:`verify ` and :ref:`upload ` the sketch:: - - int globalVar; // any function will see this variable - - void setup() { - // since "globalVar" is declared outside of any function, - // every function can "see" and use it: - globalVar = 50; - - // the variables "i" and "d" declared inside the "loop" function - // can't be seen here. see what happens when you uncomment the - // following lines, and try to Verify (compile) the sketch: - // - // i = 16; - // SerialUSB.print("i = "); - // SerialUSB.println(i); - // d = 26.5; - // SerialUSB.print("d = "); - // SerialUSB.println(d); - } - - void loop() { - // since "i" and "d" are declared inside of the "loop" function, - // they can only be seen and used from inside of it: - int i; - double d; - - for (int j = 0; j < 5; j++) { - // variable i can be used anywhere inside the "loop" function; - // variable j can only be accessed inside the for-loop brackets: - i = j * j; - SerialUSB.print("i = "); - SerialUSB.println(i); - } - - // globalVar can be accessed from anywhere. note how even - // though we set globalVar = 50 in the "setup" function, we can - // see that value here: - SerialUSB.print("globalVar = "); - SerialUSB.println(globalVar); - - // d can be accessed from anywhere inside the "loop" function: - d = 26.5; - SerialUSB.print("d = "); - SerialUSB.print(d); - SerialUSB.println(" (before separateFunction())"); - - separateFunction(); - - // notice how even though separateFunction() has a variable - // named "d", it didn't touch our (local) variable which has - // the same name: - SerialUSB.print("d = "); - SerialUSB.print(d); - SerialUSB.println(" (after separateFunction())"); - } - - void separateFunction() { - // variable "d" here has the same name as variable "d" inside of - // the "loop" function, but since they're both _local_ - // variables, they don't affect each other: - double d = 30.5; - SerialUSB.print("d = "); - SerialUSB.print(d); - SerialUSB.println(" (inside of separateFunction())"); - } - -See Also --------- - -- `C++ programming Wikibook `_. -- Wikipedia article on `scope `_ - -.. include:: cc-attribution.txt -- cgit v1.2.3