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FEATURE

Intro to Fun, Part 2

Towards Functional Programming with Real Studio

Issue: 11.1 (January/February 2013)
Author: Daniel Gross
Author Bio: Dr. Daniel Gross, the principal of Goal-oriented solutions (www.goalorientedsolutions.com), is a business and system analyst and a researcher with a keen interest in software requirements, architecture as well as software engineering methods. Dr. Gross recently discovered Real Studio while consulting a client on cross-OS development. The fun library is a result of some tinkering done to better understand Real Studio and fine-tune its impressive capabilities to produce software code that not only accomplishes its tasks, but is also easier to understand, maintain, and change.
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Article Length (in bytes): 24,011
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Article Number: 11106
Related Web Link(s):

http://en.wikipedia.org/wiki/Filter_%28higher-order_function%29
http://en.wikipedia.org/wiki/Map_%28higher-order_function%29
http://en.wikipedia.org/wiki/Currying

Excerpt of article text...

Introduction

In part one of this two-part article series I illustrated how looping functions, such as the filter [1] and map [2] functions, implemented in the fun functional library, support a functional programming style in Real Studio. I also discussed how a functional coding style helps make code easier to understand, maintain and change. In this article I illustrate two additional functional programming features offered by the fun library, functional composition and closure, and explain why they are needed and the benefits that the features offer.

The next section illustrates how to use functional composition to flexibility and add functionality to already existing code. Section three motivates the need for closure, a key concept in function programming, explains the concept and illustrates its use. Finally, I conclude the article with a discussion describing how function composition and closure was implemented in the fun library.

Functional composition in Real Studio

Let us briefly recall the example from the previous article. Figure 1 shows a Listbox with a number of selected rows. Each row stores in its RowTag a reference to a Contact object. Suppose, further, we subclass the Listbox and implement a function in the subclass that returns for all selected rows the RowTag object. Code listing 1 shows how one typically accomplishes this task:

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