## Monday, August 20, 2007

### Learning a programming language can be fun

Giles Bowkett makes a great point about how one-liner code snippets often make a great idiom in a programming language. It is always worth learning the idioms of a language than memorizing the syntax, and, as Giles mentions, a good one-liner compresses syntax down to idiom. Reading his blog, I instantly remembered the first one-liner in a programming language that gave me my first Aha! moment while learning C. The K&R bible, in Section 5.5, builds up the various versions of the C library function strcpy() that improves in conciseness and succinctness in every iteration and ultimately culminates into this power-packed one-liner ..

void strcpy(char *s, char *t) {    while (*s++ = *t++);}

In the very next paragraph, the authors mention ..

Althought this may seem cryptic at first sight, the notational convenience is considerable, and the idiom should be mastered, because you will see it frequently in C programs.

So true!

If you want to learn a programming language, invest most of your time learning the idioms - that's where you will discover the densest knowledge about using the language in the best possible way. As Giles mentions ..

But the act of compressing code into a one-liner is like the act of creating slang, and if you understand how slang comes into being, you understand how to make new words.

During my learning years of C++, one book that stood out in teaching the idioms of the language was Coplien's Advanced C++ Programming Styles and Idioms. The book was written way back in 1992, but remains my #1 recommendation for someone learning C++ even today. Many of the design patterns so popularized by the celebrated GOF book had already been beaten to hell in the Coplien book.

Often there is a fine line of misunderstanding between a syntax and an idiom ..

Many years back, in an interview for hiring a C++ developer, I had asked one candidate to explain the function prototype of a typical assignment operator overloading function. I believe that a candidate able to explain the nuances of the assignment operator overload function prototype in C++ has a good understanding of the basics of the language. Specifically I wanted him to explain the return type and value of the usual assignment operator overload function of a class in C++.

Foo& Foo::operator=(const Foo& right) {  // ..  // ..  return *this;}

• Why does the function return *this ?

• Why does the function not return right ?

• Why does the function take a reference-to-const-Foo ?

I felt this is an important idiom of C++ that developers should be thorough with, and a correct explanation by a person reveals a good understanding of multiple aspects of the language - variable lifetime, temporaries, idiomatic usage of assignment etc. Unfortunately the candidate was furious with me and complained that he does not memorize syntaxes - what are manuals for ? What he did not realize is that a proper understanding of the idiom of how assignments can be chained through references in C++ obviates the necessity of syntax memorization.

Learning a new programming language can be fun

This thread in the discussion of Lightweight Languages has an interesting list of the available options .. Amongst all of them, the most interesting one suggests to (t)ry to identify and concentrate on features of the language that are absent from other languages you know. I am sure this is a very effective way to know the idioms of a language and how to make new words with the language that you are trying to learn. Try implementing map/reduce in Javascript, lazy data structures in Erlang, Lisp like macros in Ruby - apart from the loads of fun that you will be having, you will learn the new language as well.

Every language has its own form - a Ruby program has to look like Ruby. The moment your Ruby code starts looking like Java, then you are no longer thinking in Ruby. This is the essential difference between idiomatic and non-idiomatic use of a programming language. Try exploring the following one-liner in Ruby ..

Account = Struct.new(:account_no, :account_name, :account_type)

and see how concise you can do for an equivalent Java snippet. Now that's hell of a one-liner in Ruby! And an important idiom too ..

#### 1 comment:

Anonymous said...

For ruby there's also a nifty CSV parsing regex (though not easy to grasp for beginners i guess). http://snippets.dzone.com/posts/show/4430