On 14/05/13 00:01, Daniel Magruder wrote:
I am still confused as what return does.
Having seen the other replies I'll try a slightly
different explanation.
All programs are formed by a hierarchy of functions.
You start with a top level driver block which then utilizes or calls
helper functions. Those helper functions, in turn, call other helper
functions. We can show it diagrammatically as a tree and several
software design notations exist that do this. Here is one example:
http://www.smartdraw.com/resources/tutorials/Entity-Structure-Diagrams
Since this is a text forum I'll do it in a different format...
Driver block
helper1
funcA
funcB
helper2
funcA
funcC
helper3
In this hierarchy the Driver calls 3 functions.
The helper functions call 2,2 and zero functions respectively.
funcA is called by both helper1 and helper2. When a function calls
another function it effectively pauses its own execution and hands
control to the called function.
Inside each of these 6 functions there are return statements(*) the
purpose of which is to return control to the next higher level in the
hierarchy. The function stops as soon as it reaches a return statement
and control reverts to the previous level.
Thus in funcA the first time it is called it will return to helper1.
The second time it is called it will return control to helper2.
return also has a secondary purpose which is to pass back a value to the
caller which value is the result of the functions calculations.
(*) Some functions do not have an explicit return statement. In these
cases they run to completion and control then reverts to the calling
function with an implied return value of None.
Does that help?
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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