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I'm a secondary school student currently taking the OCR Computer Science GCSE (J276). I taught myself to program and was recently surprised by the context of a question in one of OCR's specimen papers (this one) as it goes against my knowledge of programming.
In question 5b, a question goes on to ask for a description of the differences between compilers and interpreters:
Harry can use either a compiler or an interpreter to translate the code [that he has created].
This confused me, as it seemed to suggest that the code written could either be interpreted or compiled in order to run, which would be odd as it was my understanding that languages fit into one of two boxes, interpreted (python, javascript) or compiled (c++, java), rather than fitting into both.
Is it true that a single programming language can be either compiled or interpreted based on the programmer's desire, or is this another case of OCR simplifying the course to make it easier to understand?
C is a language that is usually compiled, but interpreted implementations exist.
According to #delnan in this answer,
First off, interpreted/compiled is not a property of the language but a property of the implementation. For most languages, most if not all implementations fall in one category, so one might save a few words saying the language is interpreted/compiled too, but it's still an important distinction, both because it aids understanding and because there are quite a few languages with usable implementations of both kinds (mostly in the realm of functional languages, see Haskell and ML). In addition, there are C interpreters and projects that attempt to compile a subset of Python to C or C++ code (and subsequently to machine code).
In reality, it looks like the designers of your course said something that was true in theory, but in practice tends to be more restricted. This is found all over programming and, in fact, the world in general. Could you write a JavaScript compiler for Commodore 64? Sure, the C64 implements a full, general purpose computer system, and JavaScript is Turing Complete. Just because something is possible doesn't mean that a lot of people actually do it, though, or that it is easy.
If a person learns data-structure and algorithm in one programming language does it needs to learn other language's data-structure and algorithm ?
As i am about to start a book Data-structure and algorithm in JavaScript as i also want to learn Web
will it help me for other languages too?
Data structures and algorithms are concepts that are independent of language. Therefore once you master them in you favorite language it's relatively easy to switch to another one.
Now if you're asking about built-in methods and apis that different languages have, they do differ, but you shouldn't learn specific APIs in your data-structure and algorithms book anyways.
Yes... and no.
While the concepts behind algorithms and data structures, like space and time complexity or mutability, are language agnostic, some languages might not let you implement some of those patterns at all.
A good example would be a recursive algorithm. In some languages like haskell, recursivity is the best way to iterate over a collection of element. In other languages like C, you should avoid using recursive algorithm on unbound collections as you can easily hit the dept limit of the stack. You could also easily imagine a language that is not even stack based and in which a recursive algorithm would be completely impossible to implement. You could implement a stack on top of such a language but it would most definitely be slower than implementing the algorithm in a different fashion.
An other example would be object oriented data structures. Some languages like haskell do not let you change values. All elements in such language are immutable and must be copied to be changed. This is analog to how numbers are handled in javascript where you cannot change the value 2, but you can take the value 2, add 1 to it and then store it to a new location. Other languages like C do not have (or very poorly handle) object oriented programming. This will break down most data structure pattern you will learn about in a javascript oriented book.
In the end, it all boils down to performance. You don't write C code like you write JavaScript or F# code. They all have their quirks and thus need different implementations even though the idea behind those algorithms and structures will stay the same. You can always emulate a pattern on a language that does not supports it, like OOP in C, but it will always feel more natural to solve the problem in a different way.
That being said, as long as you stay within the same kind of language, you can probably reuse 80%+ of that book. There are many OOP languages out there. Javascript is probably the most exotic of them all with its ability to treat all objects like dictionaries and its weird concept of "this" so a lot of patterns in there will not apply in those other languages.
You need not learn data structure and algorithm when you use another language.The reason is evident, all of data structures and algorithm is a realization of some kinds of "mathmatical or logical thought".
for example,if you learn the sort algorithm, you must hear about the quick sort and merge sort and any others, the realization of different sort algotithm is based on fundamental element that almost every language has,such as varible,arrays,loop and so on. i mean you can realize it without using the language(such as JavaScript) characteristics.
although it is nothing relevant to language,i still suggest you stduy it with C.The reason is that C is a lower high-level language which means it is near the operating system.And the algorithm you write with C is faster than Java or Python.(Most cases).And C don't have so many characteristic like c++ stl or java collection. In C++ or Java, it realize hashmap itself.If you are a green hand to data structure, you'd better realize it from 0 to 1 yourself rather directly use other "tools" to lazy.
The data structure and algorithm as concepts are the same across languages, the implementation however varies greatly.
Just look at the implementation of quicksort in an imperative language like C and in a functional language like Haskell. This particular algorithm is a poster boy for functional languages as it can be implemented in just about two lines (and people are particularly fond of stressing that's it).
There is a finer point. Depending on the language, many data structures and algorithms needn't be implemented explicitly at all, other than as an academic exercise to learn about them. For example, in Python you don't really need to implement an associative container whereas in C++ you need to.
If it helps, think of using DS and algo in different programming languages as narrating a story in multiple human languages. The plot elements remain the same but the ease of expression, or the lack thereof, varies greatly depending on the language used to narrate it.
(DSA) Data structures and algorithms are like emotions in humans (in all humans emotions are same like happy, sad etc)
and, programming languages are like different languages that humans speak (like spanish, english, german, arabic etc)
all humans have same emotions (DSA) but when they express them in different languages (programming languages) , the way of expressing (implementation) of these emotions (DSA) are different.
so when you switch to using different or new language, just have a look at how those DSA are implemented in that languages.
I'm really interested in becoming a serious programmer, the type that people admire for hacker chops, as opposed to a corporate drone who can't even complete FizzBuzz.
Currently I've dabbled in a few languages, most of my experience is in Perl and Shell, and I've dabbled slightly in Ruby.
However, I can't help but feel that although I know bits and pieces of languages, I don't know how to program.
I'm really in no huge rush to immediately learn a language that can land me a job (though I'd like to do it soon), and I'm considering using PLT Scheme (now called Racket) to work through How to Design Programs or Structure and Interpretation of Computer Programs, essentially, one of the Scheme classics, because I have always heard that they teach people how to write high-quality, usable, readable code.
However, even MIT changed its introductory course from using SICP and Scheme to one in Python.
So, I ask for the sage advice of the many experienced programmers here regarding the following:
Does Scheme (and do those books) really teach one how to program well? If so, which of the two books do you recommend?
Is this approach to learning still relevant and applicable? Am I on the right track?
Am I better off spending my time learning a more practical/common language like Python?
Is Scheme (or lisp in general) really a language that one learns, only to never use? Or do those of you who know a lisp code in it often?
Thanks, and sorry for the rambling.
If you want to learn to really program, start doing it. Quit dabbling and write code. Pick a language and write code. Solve problems and release applications. Work with experienced programmers on open source projects, but get doing. A lot.
Does Scheme (and do those books) really teach one how to program well? If so, which of the two books do you recommend?
Probably. Probably better than any of the Learn X in Y Timespan books.
Is this approach to learning still relevant and applicable? Am I on the right track?
Yes.
Am I better off spending my time learning a more practical/common language like Python?
Only if you plan to get a job in it. Scheme will give you a better foundation though.
Is Scheme (or lisp in general) really a language that one learns, only to never use? Or do those of you who know a lisp code in it often?
I do emacs elisp fiddling to adjust my emacs. I also work with functional languages on the side to try to keep my mind flexible.
My personal opinion is that there are essentially two tracks that need to be walked before the student can claim to know something about programming. Track one is the machine itself, the computer. You should start with assembly here and learn how the computer works. After some work and understanding there - don't skimp - you should learn C and then C++; really getting the understanding of resource management and what really happens. Track two is the very high level language track - Scheme, Prolog, Haskell, Perl, Python, C#, Java, and others that execute on a VM or interpreter lie in this area. These, too, need to be studied to learn how problems can be abstracted and thought about in different ways that do not involve the fiddly bits of a real computer.
However, what will not work is being a language dilettante when learning to program. You will need to find a language - Scheme is acceptable, although I'd recommend starting at the low level first - and then stick with that language for a good year at least.
The most important parts of Scheme are the programming-language concepts you can pick up that modern languages are now just adopting or adding support for.
Lisp and Scheme have supported, before most other languages, features that were often revolutionary for the time: closures and first-order functions, continuations, hygienic macros, and others. C has none of these.
But they're appearing more and more often in programming languages that Get Stuff Done today. Why can you just declare functions seemingly anywhere in JavaScript? What happens to outside variables you reference from within a function? What are these new "closures" that PHP 5.3 is just now getting? What are "side effects" and why can they be bad for parallel computing? What are "continuations" in Ruby? How do LINQ functions work? What's a "lambda" in Python? What's the big deal with F#?
These are all questions that learning Scheme will answer but C won't.
I'd say it depends on what you want to do.
If you want to get into programming, Python is probably better. It's an excellent first language, resembles most common programming languages, and is widely available. You'll find more libraries handy, and will be able to make things more easily.
If you want to get into computer science, I'd recommend Scheme along with SICP.
In either case, I'd recommend learning several very different languages eventually, to give you more ways to look at and solve problems. Getting reasonably proficient in Common Lisp, for example, will make you a better Java programmer. I'd take them one at a time, though.
The best languages to start with are probably:
a language you want to play/learn in
a language you want to work in
And probably in that order, too, unless the most urgent need is to feed yourself.
Here's the thing: the way to learn to program is to do it a lot. In order to do it a lot, you're going to need a lot of patience and more than a little bit of enthusiasm. This is more important than the specific language you pick.... but picking a language that you like working in (whether because you like the features or because you feel it'll teach you something) can be a big boost.
That said, here's a couple of comments on Scheme:
Does Scheme (and do those books)
really teach one how to program well?
The thing about Scheme (or something like it) is that if you learn it, it'll teach you some very useful abstractions that a lot of programmers who don't ever really come to grips with a functional programming language never learn. You'll think differently The substance of programming languages and computing will look more fluid to you. You'll have a better idea of how to compose your own quasi-primitives out of a very small set of primitives rather than relying on the generally static set of primitives offered in some other languages.
The problem is that a lot of what I'm saying might not mean much to you at the moment, and it's a bit more of a mind-bending road than coming into a common dynamic language like Perl, Python, or Ruby... or even a language like C which is close to the Von Neumann mechanics of the machine.
This doesn't mean it's necessarily a bad idea to start there: I've been part of an experiment where we taught Prolog of all things to first-time programmers, and it worked surprisingly well. Sometimes beginner's mind actually helps. :) But Scheme as a first language is definitely an unconventional path. I suspect Ruby or Python would be a gentler road.
Is Scheme (or lisp in general) really
a language that one learns, only to
never use?
It's a language that you're unlikely to be hired to program in. However, while you're learning to program, and after you've learned and are doing it in your free time, you can write code in whatever you want, and because of the Internet, you'll probably be able to find people working on open source projects in whatever language you want. :)
I hate to tell ya, but nobody admires programmers for their "hacker chops". There's people who get shit done, then there's everyone else. A great many of the former types are the "corporate drones" you appear to hold in contempt.
Now, for your question, I personally love Lisp (and Scheme), but if you want something you're more likely to use in industry "Beginning Python" might be better material for you as Python is found more often in the wild. Or if you enjoy Ruby, find some good Ruby material and start producing working solutions (same with Java or .Net or whatever).
Really, either route will serve you well. The trick is to stick with it until you've internalized the concepts being taught.
Asking whether an approach to learning is relevant and applicable is tricky - there are many different learning styles, and it's a matter of finding out which ones apply to you personally. Bear in mind that the style you like best might not be the one that actually works best for you :-)
You've got plenty of time and it sounds like you have enthusiasm to spare, so it's not a matter of which language you should learn, but which one you should learn first. personally, I'd look at what you've learnt so far, what types of languages and paradigms you've got under your belt, and then go off on a wild tangent and chose one completely different.
I started programming at a very very young age. When I was in high school, I thought I was a good programmer. That's when I started learning about HOW and WHY the languages work rather than just the syntax.
Before learning the how and why, switching to a new language would have been hell. I had learned a language, but I hadn't learned to program. Now that I know the fundamental concepts well, I can apply them to virtually any language and pick it up with ease.
I would highly recommend a book (or even a school coarse, if you can afford it) that takes you through the processes of coding without relying on a specific language.
Unfortunately I don't have any books to recommend, but if others agree with me and know of any, maybe they can offer a suggestion.
//Edit: After re-reading your question, I realize that I may have not actually answered any of them... Sorry about that. I think picking up a book that will take you in-depth with best-practices would be extremely helpful, regardless of the language you choose.
There are basic programming concepts (logic flow, data structures), which are easily taught by using languages like Python. However, there are much more complex programming concepts (design patterns, optimization, threading, etc.) which the classic languages don't abstract away for you.
If your search for knowledge leans more toward algorithm development and the science of programming, start with C. If your search is more for a practical ends, I hear Ruby is a good starting point.
I agree with gruszczy. I'd start programming with C.
It may be kind of scary at first (at least for me :S ) but in the long run you'd be grateful it. I mean I love Python, but because I learned C first, the learning curve for other languages wasn't very steep at all.
Start with C and make it so.
Just remember to practice, because you'll never improve at something by doing nothing. ;)
To a specific point in your question, the "classics" you mention will help you with exactly what the titles say. SICP is about the structure and interpretation of computer programs. It is not about learning Scheme (though you will learn Scheme). HtDP is about how to design programs, it is not about learning Scheme (though you will learn Scheme).
Scheme, in principle, is a very small and concise language with almost no gotchas. This makes it excellent for moving on to learning how to structure and interpret programs, or how to design them. More traditional "practical" languages like C, C++, Python, or Java do not have this quality. They are rife with syntax. Learning with these languages means you must simultaneously learn syntactical quirks while learning to think like a programmer. In my opinion, this is unfortunate. In some cases the quirks are good, in others they are accidents of history, but in all cases it is unfortunate.
Start coding in C. It should be a horror for you at first, but this teaches you most important stuff like: pointers, recurrence, memory management. Try reading some classic books about programming like The Art of Computer Programming by Donald Knuth. After you master that, you can think about learning object oriented programming or functional programming. First basics. If fou manage to learn them, nothing will be hard for you ever again.
if i like Ruby a lot, is there a reason I should learn another language now, such as Lua or Erlang?
New programming languages, much like spoken languages, can open up new perspectives. Learning new languages -- especially ones rather different from what you're used to (and Erlang will probably fit that bill) -- can teach you a lot of different things you didn't even know you didn't know about programming. So yes, I think you absolutely should, even if you just learn enough to tinker with it and get a feel for the new language.
Learning a functional language in particular can be extremely beneficial. Becoming familiar with the functional style of programming is a surefire step toward becoming a better programmer. Lisp (or its derivatives) in particular is a good language to study. Here's a list of past thread on SO that might offer you some insight along these lines:
Why do people think functional programming will catch on?
What’s a good Functional language to learn?
Benefits of learning scheme?
Leaving aside the (excellent) general reasons to want to learn another language, if you like Ruby a lot you might want to
Learn Smalltalk, which is a language very, very similar to Ruby but in purer form.
Learn a language that is very, very different—say something that is based on algebraic data types and functions rather than objects and methods, and something with a static type system rather than a dynamic type system—but something that, like Ruby, will support powerful methods of program composition and generic programming. Good candidates would include Standard ML and Haskell.
Learn a language that is very, very different—say something that makes you control every bit, address, and word in memory—something that forces you to understand and take control of the hardware. In other words, learn C.
Regarding the other languages you mention,
Lua is small and very elegantly designed and implemented. That may appeal to the Rubyist in you. But unlike Ruby it does not impose much of a worldview; it is more of a collection of piece parts. I would suggest you're more likely to appreciate and enjoy Lua after you've worked in three or four other languages first.
Erlang is interesting, but I have a gut feel it's either too different (purely functional, distributed) or not different enough (dynamic type system). But if it appeals to you, go for it.
On the other hand, there's something to be said for really knowing a language well. You'll be able to do a lot more with in-depth knowledge of a single language than you will with surface knowledge of a dozen.
If you like Ruby a lot you should definitely learn another language... one without sigils if possible.
Seems to me that a professional learns the tools he needs to use. Frameworks, containers, languages, all are fair game. I started out in Pascal, went to C and then C++. Then converted to Java. These days its mostly Java with a lot of Javascript and some PHP. Easy enough right? Well, I also need to learn Bash scripting and Perl. Never mind all the other crap I need to get on top of (if you say you understand all of web authentication I will call you a liar). There's a lot of stuff out there. Jump in. Be willing to try different things.
I always enjoy learning new languages for the mere challenge of it. It keeps my brain fit. I've also found it makes for good job interview fodder to be able to say "I'm flexible. I'm adaptable to whatever your needs may be in the future. And I can prove it with my long list of languages."
My main language is PHP. I am a script language fan, nevertheless I have dived into C#, Java, Python, Ruby and even OO JavaScript books to find new mechanisms, ways of thinking. I have found pretty many stunts in Java for example, that I could implement in my all day work. So learning or just studying new languages can widen your perspective.
I've just started one of my courses, as classes just began 2 weeks ago, and we are learning Scheme right now in one for I assume some reason later on, but so far from what he is teaching is basically how to write in scheme. As I sit here trying to stay awake I'm just trying to grasp why I would want to know this, and why anyone uses it. What does it excel at? Next week I plan to ask him, whats the goal to learn here other than just how to write stuff in scheme.
It's a functional programming language and will do well broaden your experience.
Even if you don't use it in the real world doesn't mean it doesn't have any value. It will help you master things like recursion and help to force you to think of problems in different ways than you normally would.
I wish my school forced us to learn a functional programming language.
Languages like LISP (and the very closely related Scheme) are to programming what Latin is to English.
You may never speak Latin a day in your normal life again after taking a course, but simply learning a language like Latin will improve your ability to use English.
The same is true for Scheme.
I see all these people here saying that while they would never actually use Scheme again it's nevertheless been a worthwhile language to learn because it forces a certain way of thinking. While this can be true, I would hope that you would learn Scheme because you eventually will find it useful and not simply as an exercise in learning.
Though it's not blazingly fast like a compiled language, nor is it particularly useful at serving websites or parsing text, I've found that Scheme (and other lisps by extension) has no parallel when it comes to simplicity, elegance, and powerful functional manipulation of complex data structures. To be honest, I think in Scheme. It's the language I solve problems in. Don't give up on or merely tolerate Scheme - give it a chance and it won't disappoint you.
By the way, the best IDE for Scheme is DrScheme, and it contains language extensions to do anything you can do in another language, and if you find something it can't you can just use the C FFI and write it yourself.
I would suggest to keep an open mind when learning. Most of the time in school we don't fully comprehend what/why we are learning a particular subject. But as I've experienced about a million times in life, it turns out to be very useful and at the very least being aware of it helps you. Scheme, believe it or not, will make you a better programmer.
Some people say Scheme's greatest strength is as a teaching language. While it is very beneficial to learn functional programming (it's an entirely new way of thinking) another benefit in learning scheme is that it is also "pure". Sure it can't do a ton of stuff like java, but that's also what's great about it, it's a language made entirely of parentheses, alphanumeric characters, and a mere handful other punctuations.
In my intro course, we are taught Java, and I see lots of my friends struggling with 'public static void main' even though that's not the point of the program and how the profs have no choice but to 'handwave' it until they're more advanced. You don't see that in Scheme.
If you really want to learn what Scheme can do in a piece of cake that is really hard to implement in languages like Java, I suggest looking at this: http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-12.html#%_sec_1.3
This is probably the best book written on Scheme.
Scheme was used by NASA to program some of the Mars rovers. It's usage in the marketplace is pretty specific, but like I'm sure your teachers are telling you, the things you learn in Scheme will carry over to programming in general.
Try not to get caught up on details like the parenthesis, and car/cdr. Most of what you're learning translates to other languages in one way or another. Don't worry about whether or not you can take Scheme to the market place, chances are you'll be learning some other more marketable languages in other classes. What you are learning here is more important.
If you are learning scheme, you can learn all about how object systems are implemented (hint: an object system isn't always about a type that has methods and instance variables bound to it...). While this kind of knowledge won't help in 95% of your daily work, for 5% of your work you will depend on that knowledge.
Additionally, you can learn about completely different styles of computation, such as streams/lazy evaluation, or even logic programming. You could also learn more about how computer programs in general are interpreted; from the basics in how program code is evaluated, to more deeper aspects like making your own interpreter and compiler). Knowing this kind of information is what separates a good programmer from a great programmer.
Scheme is not really a Functional language, it's more method agnostic then that. Perhaps more to the point, Scheme is an excellent language to choose if you want to explore with different methods of computation. As an example, a highly parallel functional language "Termite" was built on top of Scheme.
In short, the point in learning scheme is so that you can learn the fundamentals of programming.
If you need some help in making programming in scheme more enjoyable, don't be afraid to ask. A lot of programmers get hung up on (for instance) the parenthesis, when there are perfectly great ways to work with scheme source code that makes parenthesis something to cherish, rather then hate. As an example, emacs with paredit-mode,some kind of scheme interaction mode and highlight-parenthesis-mode is pretty awesome.
My problem was when learning this we learned clisp right along with it. I couldn't keep the two strait to save my life.
What I did learn from them though was how to write better c and java code. This is simply because of the different programming style I learned. I have adapted more of the functional style into some of my programming and It has helped me in some cases.
I would never want to program in scheme or lisp again if I didn't have to, but I am glad that I at least did a little in them just to learn the different way to program.
Functional languages like Scheme have great application to mathematics, artificial intelligence, linguistics, and other highly theoretical areas of computer science (machine learning, natural language processing, etc). This is due to the purity of functional programming languages, which have no side effects, as well as their ability to navigate higher-order procedures with ease. A strong knowledge of functional programming languages is critical for solving many of the questions which hover just beyond the frontier of computer science. As a bonus, you'll get great with higher-order procedures and recursion.