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What is, in your opinion, the most surprising, weird, strange or really "WTF" language feature you have encountered?

Please only one feature per answer.

Answered By: Edan Maor ( 1869)

In C, arrays can be indexed like so:

a[10]

which is very common.

However, the lesser known form (which really does work!) is:

10[a]

which means the same as the above.

Is there a set of things that every JavaScript programmer should know to be able to say "I know JavaScript"?

Answered By: bobince ( 593)

Not jQuery. Not YUI. Not (etc. etc.)

Frameworks may be useful, but they are often hiding the sometimes-ugly details of how JavaScript and the DOM actually work from you. If your aim is to be able to say “I know JavaScript”, then investing a lot of time in a framework is opposed to that.

Here are some JavaScript language features that you should know to grok what it's doing and not get caught out, but which aren't immediately obvious to many people:

  • That object.prop and object['prop'] are the same thing (so can you please stop using eval, thanks); that object properties are always strings (even for arrays); what for...in is for (and what it isn't).

  • Property-sniffing; what undefined is (and why it smells); why the seemingly-little-known in operator is beneficial and different from typeof/undefined checks; hasOwnProperty; the purpose of delete.

  • That the Number datatype is really a float; the language-independent difficulties of using floats; avoiding the parseInt octal trap.

  • Nested function scoping; the necessity of using var in the scope you want to avoid accidental globals; how scopes can be used for closures; the closure loop problem.

  • How global variables and window properties collide; how global variables and document elements shouldn't collide but do in IE; the necessity of using var in global scope too to avoid this.

  • How the function statement acts to ‘hoist’ a definition before code preceding it; the difference between function statements and function expressions; why named function expressions should not be used.

  • How constructor functions, the prototype property and the new operator really work; methods of exploiting this to create the normal class/subclass/instance system you actually wanted; when you might want to use closure-based objects instead of prototyping. (Most JS tutorial material is absolutely terrible on this; it took me years to get it straight in my head.)

  • How this is determined at call-time, not bound; how consequently method-passing doesn't work like you expect from other languages; how closures or Function#bind may be used to get around that.

  • Other ECMAScript Fifth Edition features like indexOf, forEach and the functional-programming methods on Array; how to fix up older browsers to ensure you can use them; using them with inline anonymous function expressions to get compact, readable code.

  • The flow of control between the browser and user code; synchronous and asynchronous execution; events that fire inside the flow of control (eg. focus) vs. events and timeouts that occur when control returns; how calling a supposedly-synchronous builtin like alert can end up causing potentially-disastrous re-entrancy.

  • How cross-window scripting affects instanceof; how cross-window scripting affects the control flow across different documents; how postMessage will hopefully fix this.

See this answer regarding the last two items.

Most of all, you should be viewing JavaScript critically, acknowledging that it is for historical reasons an imperfect language (even more than most languages), and avoiding its worst troublespots. Crockford's work on this front is definitely worth reading (although I don't 100% agree with him on which the “Good Parts” are).

It wasn't that long ago that I was a beginning coder, trying to find good books/tutorials on languages I wanted to learn. Even still, there are times I need to pick up a language relatively quickly for a new project I am working on. The point of this post is to document some of the best tutorials and books for these languages. I will start the list with the best I can find, but hope you guys out there can help with better suggestions/new languages. Here is what I found:

Since this is now wiki editable, I am giving control up to the community. If you have a suggestion, please put it in this section. I decided to also add a section for general be a better programmer books and online references as well. Once again, all recommendations are welcome.

General Programming

Online Tutorials
Foundations of Programming By Karl Seguin - From Codebetter, its C# based but the ideas ring true across the board, can't believe no-one's posted this yet actually.
How to Write Unmaintainable Code - An anti manual that teaches you how to write code in the most unmaintable way possible. It would be funny if a lot of these suggestions didn't ring so true.
The Programming Section of Wiki Books - suggested by Jim Robert as having a large amount of books/tutorials on multiple languages in various stages of completion
Just the Basics To get a feel for a language.

Books
Code Complete - This book goes without saying, it is truely brilliant in too many ways to mention.
The Pragmatic Programmer - The next best thing to working with a master coder, teaching you everything they know.
Mastering Regular Expressions - Regular Expressions are an essential tool in every programmer's toolbox. This book, recommended by Patrick Lozzi is a great way to learn what they are capable of.
Algorithms in C, C++, and Java - A great way to learn all the classic algorithms if you find Knuth's books a bit too in depth.

C

Online Tutorials
This tutorial seems to pretty consise and thourough, looked over the material and seems to be pretty good. Not sure how friendly it would be to new programmers though.
Books
K&R C - a classic for sure. It might be argued that all programmers should read it.
C Primer Plus - Suggested by Imran as being the ultimate C book for beginning programmers.
C: A Reference Manual - A great reference recommended by Patrick Lozzi.

C++

Online Tutorials
The tutorial on cplusplus.com seems to be the most complete. I found another tutorial here but it doesn't include topics like polymorphism, which I believe is essential. If you are coming from C, this tutorial might be the best for you.

Another useful tutorial, C++ Annotation. In Ubuntu family you can get the ebook on multiple format(pdf, txt, Postscript, and LaTex) by installing c++-annotation package from Synaptic(installed package can be found in /usr/share/doc/c++-annotation/.

Books
The C++ Programming Language - crucial for any C++ programmer.
C++ Primer Plus - Orginally added as a typo, but the amazon reviews are so good, I am going to keep it here until someone says it is a dud.
Effective C++ - Ways to improve your C++ programs.
More Effective C++ - Continuation of Effective C++.
Effective STL - Ways to improve your use of the STL.
Thinking in C++ - Great book, both volumes. Written by Bruce Eckel and Chuck Ellison.
Programming: Principles and Practice Using C++ - Stroustrup's introduction to C++.
Accelerated C++ - Andy Koenig and Barbara Moo - An excellent introduction to C++ that doesn't treat C++ as "C with extra bits bolted on", in fact you dive straight in and start using STL early on.

Forth

Books
FORTH, a text and reference. Mahlon G. Kelly and Nicholas Spies. ISBN 0-13-326349-5 / ISBN 0-13-326331-2. 1986 Prentice-Hall. Leo Brodie's books are good but this book is even better. For instance it covers defining words and the interpreter in depth.

Java

Online Tutorials
Sun's Java Tutorials - An official tutorial that seems thourough, but I am not a java expert. You guys know of any better ones?
Books
Head First Java - Recommended as a great introductory text by Patrick Lozzi.
Effective Java - Recommended by pek as a great intermediate text.
Core Java Volume 1 and Core Java Volume 2 - Suggested by FreeMemory as some of the best java references available.
Java Concurrency in Practice - Recommended by MDC as great resource for concurrent programming in Java.

The Java Programing Language

Python

Online Tutorials
Python.org - The online documentation for this language is pretty good. If you know of any better let me know.
Dive Into Python - Suggested by Nickola. Seems to be a python book online.

Perl

Online Tutorials
perldoc perl - This is how I personally got started with the language, and I don't think you will be able to beat it.
Books
Learning Perl - a great way to introduce yourself to the language.
Programming Perl - greatly referred to as the Perl Bible. Essential reference for any serious perl programmer.
Perl Cookbook - A great book that has solutions to many common problems.
Modern Perl Programming - newly released, contains the latest wisdom on modern techniques and tools, including Moose and DBIx::Class.

Ruby

Online Tutorials
Adam Mika suggested Why's (Poignant) Guide to Ruby but after taking a look at it, I don't know if it is for everyone. Found this site which seems to offer several tutorials for Ruby on Rails.
Books
Programming Ruby - suggested as a great reference for all things ruby.

Visual Basic

Online Tutorials
Found this site which seems to devote itself to visual basic tutorials. Not sure how good they are though.

PHP

Online Tutorials
The main PHP site - A simple tutorial that allows user comments for each page, which I really like. PHPFreaks Tutorials - Various tutorials of different difficulty lengths.
Quakenet/PHP tutorials - PHP tutorial that will guide you from ground up.

JavaScript

Online Tutorials
Found a decent tutorial here geared toward non-programmers. Found another more advanced one here. Nickolay suggested A reintroduction to javascript as a good read here.

Books
Head first JavaScript
JavaScript: The Good Parts (with a Google Tech Talk video by the author)

C#

Online Tutorials
C# Station Tutorial - Seems to be a decent tutorial that I dug up, but I am not a C# guy.
C# Language Specification - Suggested by tamberg. Not really a tutorial, but a great reference on all the elements of C#
Books
C# to the point - suggested by tamberg as a short text that explains the language in amazing depth

ocaml

Books
nlucaroni suggested the following:
OCaml for Scientists Introduction to ocaml
Using Understand and unraveling ocaml: practice to theory and vice versa
Developing Applications using Ocaml - O'Reilly
The Objective Caml System - Official Manua

Haskell

Online Tutorials
nlucaroni suggested the following:
Explore functional programming with Haskell
Books
Real World Haskell
Total Functional Programming

LISP/Scheme

Books
wfarr suggested the following:
The Little Schemer - Introduction to Scheme and functional programming in general
The Seasoned Schemer - Followup to Little Schemer.
Structure and Interpretation of Computer Programs - The definitive book on Lisp (also available online).
Practical Common Lisp - A good introduction to Lisp with several examples of practical use.
On Lisp - Advanced Topics in Lisp
How to Design Programs - An Introduction to Computing and Programming
Paradigms of Artificial Intelligence Programming: Case Studies in Common Lisp - an approach to high quality Lisp programming

What about you guys? Am I totally off on some of there? Did I leave out your favorite language? I will take the best comments and modify the question with the suggestions.

Answered By: Kristopher Johnson ( 33)

I know this is going to seem old-fashioned, but I don't think much of using online tutorials to learn programming languages or platforms. These generally give you no more than a little taste of the language. To really learn a language, you need the equivalent of a "book", and in many cases, this means a real dead-tree book.

If you want to learn C, read K&R. If you want to learn C++, read Stroustrup. If you want to learn Lisp/Scheme, read SICP. Etc.

If you're not willing to spend more than $30 and a few hours to learn a language, you probably aren't going to learn it.

It seems to be a mainstream opinion that assembly programming takes longer and is more difficult to program in than a higher level language such as C. Therefore it seems to be recommend or assumed that it is better to write in a higher level language for these reasons and for the reason of better portability.

Recently I've been writing in x86 assembly and it has dawned on me that perhaps these reasons are not really true, except perhaps portability. Perhaps it is more of a matter of familiarity and knowing how to write assembly well. I also noticed that programming in assembly is quite different than programming in an HLL. Perhaps a good and experienced assembly programmer could write programs just as easily and as quickly as an experienced C programmer writing in C.

Perhaps it is because assembly programming is quite different than HLLs, and so requires different thinking, methods and ways, which makes it seem very awkward to program in for the unfamiliar, and so gives it its bad name for writing programs in.

If portability isn't an issue, then really, what would C have over a good assembler such as NASM?

Edit: Just to point out. When you are writing in assembly, you don't have to write just in instruction codes. You can use macros and procedures and your own conventions to make various abstractions to make programs more modular, more maintainable and easier to read. This is where being familiar with how to write good assembly comes in.

Answered By: Benoit ( 334)

ASM has poor legibility and isn't really maintainable compared to higher-level languages.

Also, there are many fewer ASM developers than for other more popular languages, such as C.

Furthermore, if you use a higher-level language and new ASM instructions become available (SSE for example), you just need to update your compiler and your old code can easily make use of the new instructions.

What if the next CPU has twice as many registers?

The converse of this question would be: What functionality do compilers provide?

I doubt you can/want to/should optimize your ASM better than gcc -O3 can.

When all you have is a pair of bolt cutters and a bottle of vodka, everything looks like the lock on the door of Wolf Blitzer's boathouse. (Replace that with a hammer and a nail if you don't read xkcd)

I currently program Clojure, Python, Java and PHP, so I am familiar with the C and LISP syntax as well as the whitespace thing. I know imperative, functional, immutable, OOP and a couple type systems and other things. Now I want more!

What are languages that take a different approach and would be useful for either practical tool choosing or theoretical understanding?

I don't feel like learning another functional language(Haskell) or another imperative OOP language(Ruby), nor do I want to practice impractical fun languages like Brainfuck.

One very interesting thing I found myself are monoiconic stack based languages like Factor.

Only when I feel I understand most concepts and have answers to all my questions, I want to start thinking about my own toy language to contain all my personal preferences.

Answered By: fogus ( 289)

Matters of practicality are highly subjective, so I will simply say that learning different language paradigms will only serve to make you a better programmer. What is more practical than that?

Functional, Haskell - I know you said that you didn't want to, but you should really really reconsider. You've gotten some functional exposure with Clojure and even Python, but you've not experienced it to its fullest without Haskell. If you're really against Haskell then good compromises are either ML or OCaml.

Declarative, Datalog - Many people would recommend Prolog in this slot, but I think Datalog is a cleaner example of a declarative language.

Array, J - I've only just discovered J, but I find it to be a stunning language. It will twist your mind into a pretzel. You will thank J for that.

Stack, Factor/Forth - Factor is very powerful and I plan to dig into it ASAP. Forth is the grand-daddy of the Stack languages, and as an added bonus it's simple to implement yourself. There is something to be said about learning through implementation.

Dataflow, Oz - I think the influence of Oz is on the upswing and will only continue to grow in the future.

Prototype-based, JavaScript / Io / Self - Self is the grand-daddy and highly influential on every prototype-based language. This is not the same as class-based OOP and shouldn't be treated as such. Many people come to a prototype language and create an ad-hoc class system, but if your goal is to expand your mind, then I think that is a mistake. Use the language to its full capacity. Read Organizing Programs without Classes for ideas.

Expert System, CLIPS - I always recommend this. If you know Prolog then you will likely have the upper-hand in getting up to speed, but it's a very different language.

Frink - Frink is a general purpose language, but it's famous for its system of unit conversions. I find this language to be very inspiring in its unrelenting drive to be the best at what it does. Plus... it's really fun!

Functional+Optional Types, Qi - You say you've experience with some type systems, but do you have experience with "skinnable* type systems? No one has... but they should. Qi is like Lisp in many ways, but its type system will blow your mind.

Actors+Fault-tolerance, Erlang - Erlang's process model gets a lot of the buzz, but its fault-tolerance and hot-code-swapping mechanisms are game-changing. You will not learn much about FP that you wouldn't learn with Clojure, but its FT features will make you wonder why more languages can't seem to get this right.

Enjoy!