Better Software - December 2007 - (Page 12)

Code Craft What does D have that Java doesn’t? Here’s a partial list: stand-alone functions, nested functions, delegates, inline assembler, native-code compilation, deterministic destruction of objects for automatic resource management (“scope guards”), compile-time programming (a.k.a. metaprogramming), type inference (see the program in listing 5), and built-in support for automated unit testing and contract programming. In listing 5, the sample D program counts the number of occurrences of words in text files and lists the results alphabetically. Running this program on the previous sentence yields the output in Listing 6. The call to std.string.split takes the string returned from std.stdio.read (which is actually a byte array, hence the cast) and splits on whitespace. The auto keyword declares words to be the same type as the output from split, which here is a dynamic array of strings. Counts is an associative array (a.k.a. a map or hash) with string // wc.d: Counts the number of occurrences of each word in a text file keys and integer values. The foreach import std.stdio; keyword is D’s generic iterator conimport std.string; struct. Associative arrays have a keys import std.file; property that returns the keys as an array, and arrays have a sort proper// This function does all the work (Reads words into a list; ty that sorts the array in place. The // computes counts; displays results) expression [1..$] is an array slice, in void wc(string filename) { this case comprising the second slot auto words = split(cast(string) read(filename)); through the end of the array (denoted int[string] counts; by $). Slices are composable, mutable foreach (word; words) views into an array—no copies are ++counts[word]; made. foreach (w; counts.keys.sort) D’s power and readability have apwritefln("%s: %d", w, counts[w]); pealed to a large audience in a short } time, hence the favorable TIOBE ranking. Already in version 2.0, D // A simple driver: process all file arguments held its first Developers’ Conference void main(string[] args) { in August 2007 in Seattle, sponsored foreach(f; args[1..$]) { // Start at second arg ([1]) by Amazon. If you are looking for a writefln("\n%s:", f); high-level, type-safe language with the wc(f); efficiency of C++ and the convenience } of Java or C# and then some, D might } be the language for you. You can find information regarding all things D at Listing 5 digitalmars.com. {end} text.dat: 5,: 1 D: 1 In: 1 alphabetically.: 1 and: 1 counts: 1 in: 1 listing: 1 lists: 1 number: 1 occurrences: 1 of: 2 program: 1 results: 1 sample: 1 text: 1 the: 3 words: 1 Chuck Allison developed software for twenty years before becoming a professor of computer science at Utah Valley State College. He was senior editor of the C/C++ Users Journal and is founding editor of The C++ Source. He is also the author of two C++ books and gives onsite training in C++, Python, and Design Patterns. Sticky Notes For more on the following topic go to www.StickyMinds.com/bettersoftware. I TIOBE Are you marketable? In how many of the top-twenty languages are you fluent? Which are your favorites? M Listing 6 Follow the link on the StickyMinds.com homepage to join the conversation. 12 BETTER SOFTWARE DECEMBER 2007 www.StickyMinds.com digitalmars.com www.StickyMinds.com/bettersoftware StickyMinds.com www.StickyMinds.com

Table of Contents Feed for the Digital Edition of Better Software - December 2007

Better Software - December 2007 Contents Mark Your Calendar What's Happening @ StickyMinds.com Technically Speaking Code Craft Test Connection Management Chronicles Man and Machine Let Your Values be Your Guide A Story About User Stories and Test-driven Development Product Announcements The Last Word Ad Index

Better Software - December 2007

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