You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
112 lines
4.6 KiB
112 lines
4.6 KiB
Control statements are almost exactly as they sound, statements that control our programs.
|
|
Well, they control the flow of our code.
|
|
With control statements we can change the course of our programs based on various conditions.
|
|
|
|
\subsection{If Statements}
|
|
If stataments allow us to execute a given block of code based on a given condition.
|
|
There are three main parts to an if statement \pigVal{if}, the \pigVal{conditional} and a \pigVal{code block}.
|
|
|
|
|
|
\begin{lstlisting}[caption={If Statement}]
|
|
name = ``brett''
|
|
|
|
if( name == ``brett'' )
|
|
print ``Name is brett''
|
|
\end{lstlisting}
|
|
|
|
In this simple example the code block \pigOut{print ``Name is brett''} will only execute if the conditional \pigOut{name == ``brett''} is true.
|
|
So the output of this code will be \pigOut{Name is brett}.
|
|
|
|
\begin{lstlisting}[caption={False If Statement}]
|
|
name = ``brett''
|
|
|
|
if( name == ``john'' )
|
|
print ``Name is john''
|
|
\end{lstlisting}
|
|
|
|
In this example there will be no output, this is because the conditional \pigOut{name == ``john''} equates to false so the code block \pigOut{print ``Name is john''} will never get executed.
|
|
|
|
\subsection{If-Else Statements}
|
|
If statements are great and help us execute portions of our code based on the values of other variables, including based on input from users.
|
|
But what if the condition of the if statement equates to false?
|
|
With if statements we can append an else statement and a block of code to the end of an if statement that will get called if the if statement is false.
|
|
|
|
\begin{lstlisting}[caption={If-Else Statement}]
|
|
name = ``brett''
|
|
|
|
if name == ``john'':
|
|
print ``Name is john''
|
|
else:
|
|
print ``Name is not john''
|
|
\end{lstlisting}
|
|
|
|
The output of this program will be \pigOut{Name is not john}.
|
|
When the program hits the if statement it evaluates the conditional \pigVar{name == ``john''} which evaluates to \pigVal{false}.
|
|
Normally the program will continue on its way but since we provided an else statement that gets executed instead.
|
|
An If-Else statement allows us to program ``if this then do this, otherwise do this.''
|
|
|
|
\subsection{Else If Statements}
|
|
Ok... wait, we just did If-Else statements not we are doing Else if statements?
|
|
Yes, but they are different I swear!
|
|
An If-Else statement allows us to execute code regardless of whether a conditional is true or false but with an else if statement we can provide multiple conditionals to an if statements.
|
|
|
|
\begin{lstlisting}[caption={Else If Statement}]
|
|
name = ``brett''
|
|
|
|
if name == ``john'':
|
|
print ``Name is john''
|
|
else if name == ``brett''
|
|
print ``Name is brett''
|
|
\end{lstlisting}
|
|
|
|
See? I told you it was different.
|
|
So the output of this program is \pigOut{Name is brett} and this is because when the program gets to the if statement and evaluates it as false, it then continues down the list of conditionals.
|
|
This works similar to how the else statement before worked, but this time we are giving the if statement multiple conditionals to check.
|
|
We can expand this example by adding more else if statements.
|
|
|
|
\begin{lstlisting}[caption={Else If Statement 2}]
|
|
name = ``brett''
|
|
|
|
if name == ``john'':
|
|
print ``Name is john''
|
|
else if name == ``brett''
|
|
print ``Name is brett''
|
|
else if name == ``barbara'':
|
|
print ``Name is barbara''
|
|
\end{lstlisting}
|
|
|
|
Just like the first example this program will ouput \pigOut{Name is brett}.
|
|
This is because when the program gets to \pigVar{name == ``john''} it evaluates to false causing the program to skip to the next conditional \pigVar{name ==''brett''}, which then evaluates to true causing the code block given to execute.
|
|
The last conditional \pigVar{name == ``barbara''} will then be skipped and the program will continue past the if statement.
|
|
\par
|
|
|
|
Now... what is we add an else statement to the end of this?
|
|
With an if statement we could append an else statement to the end telling it what to do if the conditional failed.
|
|
With an else if statement we can also append an else statement to the end telling it what to do if all of the conditionals fail.
|
|
|
|
\begin{lstlisting}[caption={Else If Else Statement}]
|
|
name = ``brett''
|
|
|
|
if name == ``john'':
|
|
print ``Name is john''
|
|
else if name == ``barbara'':
|
|
print ``Name is barbara''
|
|
else:
|
|
print ``Well, I'm not sure what your name is''
|
|
\end{lstlisting}
|
|
|
|
This program will output \pigOut{Well, I'm not sure what your name is} because both conditionals, \pigVar{name == ``john''} and \pigVar{name == ``barbara''}, evaluate to false causing the if statement to continue on its merry way.
|
|
|
|
\subsection{For Loops}
|
|
|
|
\subsection{While Loops}
|
|
|
|
\subsection{Do-While Loops}
|
|
|
|
\subsection{Switch Stataments}
|
|
|
|
\subsection{Break Statments}
|
|
|
|
\subsection{Continue Stataments}
|
|
|
|
\subsection{Conclusion}
|