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[[Category: Analytica User Guide]]
<breadcrumbs> Analytica User Guide > Procedural Programming > {{PAGENAME}}</breadcrumbs><br />

The following function, <code>Factors()</code>, computes the prime factors of an integer x. It illustrates many of the key constructs of procedural programming.

::[[File:example1.png|400px]]

See below for an explanation of each of these constructs, and cross references to where they are.

::{| border="0;" style="width:400px;"
! '''Numbers identify<br />
features below'''
! '''Function Factors(x)<br />
Definition:'''
|-
| 1
| <code>VAR result := [1];</code>
|-
| 2
| <code>VAR n := 2;</code>
|-
| 3
|<code>WHILE n <= x DO</code>
|-
| 4
|<code>BEGIN</code>
|-
| 2
| <code>VAR r := Floor(x/n);</code> 
<code>IF r*n = x THEN</code>
|-
| 5
|<code>(result := Concat(result, [n]);</code>
|-
| 6
| <code>x := r)</code>
<code>ELSE n := n + 1</code>
|-
| 4,7
|<code>END; /* End While loop */</code>
|-
| 7, 8
|<code>result /* End Definition */</code>
|}

This definition illustrates these features:

# <code>VAR x := e</code> construct defines a local variable x, and sets an initial value e. See [http://wiki.analytica.com/index.php?title=Local_Variables#Defining_a_local_variable Defining a Local Variable].
# You can group several expressions (statements) into a definition by separating them using “;” (semicolons). Expressions can be on the same line or successive lines. See [http://wiki.analytica.com/index.php?title=Begin-End_for_Grouping_Expressions Begin-End for Grouping Expressions].
# <code>While test Do body</code> construct tests condition <code>Test</code>, and, if True, evaluates <code>Body</code>, and repeats until condition <code>Test</code> is False. See [http://wiki.analytica.com/index.php?title=For_and_While_Loops#While.28Test.29_Do_Body While(Test) Do Body].
# Begin <code>e1; e2; … End</code> groups several expressions separated by semicolons “;” — in this case as the body of a While loop. See “Begin-End, (), and “;” for grouping expressions” on page 376.
#  <code>(e1; e2; …)</code> is another way to group expressions — in this case, as the action to be taken in the Then case. See [http://wiki.analytica.com/index.php?title=Begin-End_for_Grouping_Expressions Begin-End for Grouping Expressions].
#  <code>x := e</code> lets you assign the value of an expression <code>e</code> to a local variable <code>x</code> or, as in the first case, to a parameter of a function. See [http://wiki.analytica.com/index.php?title=Local_Variables#Assigning_to_a_local_variable: Assigning to a local variable].
#  A comment is enclosed between /* and */ as an alternative to { and }.
#  A group of expressions returns the value of the last expression — here the function <code>Factors</code> returns the value of <code>result</code> — whether the group is delimited by Begin and End, by parentheses marks ( and ), or, as here, by nothing.<br />


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