Been working with Javascript for a couple of years, and recently I've been using lua quite a lot.
My only big beef with these languages are that they use weak typing. And I'm wondering if someone has good answer to; why?
The way I personally see it, there are no advantages what so ever. My colleague suggested that it might be because strong typing would require a lot of type checks, so it would hurt performance quite a lot. But as someone who's a bit oblivious as to how compilers work, I struggle to accept this explanation.
(Sorry if this is a dumb question, I've seen a similar discussion here but I disagree with the both the question and the answer. Prototyping is just as easy to do with a language that uses strong typing.)
Dynamic (runtime) type-checking does result in a performance hit. Keep in mind that compiled languages like C++, Java, and C# can enforce the type system at compile time (i.e. if you write code that violates the type system it won't even compile, far less run), which allows you to skip a lot of the runtime type checking you would've had to do otherwise. There is no such mechanism in scripting languages, so you'd have to do extra checking.
Quite apart from the performance implications, type checking requires a fairly complex set of rules which both the implementor and (to some extent) the user has to understand. Strict type checking also gets in the way of convenience even for advanced users who know what they are doing and might generally be able to put up with and even appreciate type checking for some of their variables. Indeed, some modern script languages now offer optional type checking for users who want it.
Related
While reading "Python scripting for computational science" I came across the following text in the section discussing generators:
Whether to rapidly write a generator or to implement the class methods __iter__ and __next__ depends on the application, personal tast, readibility, and complexity of the iterator. Since generators are very compact and unfamiliar to most programmers, the code often becomes less readable than a corresponding version using __iter__ and __next__.
This led me to wonder whether unfamiliarity (of other programmers) is a good reason NOT to use relatively new and powerful features of a language (like Python generators).
If you don't use it, how can it ever become popular and familiar?
So, my question: is unfamiliarity sometimes a good reason not to use new language features?
Your own unfamiliarity with a language feature may be a good reason to tread lightly. For example, in C#, if you aren't certain about the differences between object y = func1() ?? func2(); and object y = func1() != null ? func1() : func2(); (hint: left-to-right order of evaluation), then maybe you are better off writing the corresponding if clause just because it's clearer what actually is going on. Someone who knows the nuances of the language better may very well come around and refactor later, and in the meantime, the cost is usually low.
However, if you know how to use a language feature, I see little reason to avoid using it simply because others may find it difficult to understand. If you really feel the need to, then add a comment (such as, perhaps, "?? is the _null coalescing operator_") to help fellow developers know what to look for if they can't figure out from the code alone what it is doing, and you are afraid that they may have to go it alone.
This, mind you, is about production code. Experimenting certainly has its place, but its place is not necessarily in the mainline codebase. I always keep a "scratch" project handy for when I want to try something out without risking impact to anything else. There, I often take liberties far beyond those I take in production or to-be-production code.
I wouldn't say that unfamilarity is a good reason to not use new language features. Or for that matter, use new languages.
Lack of support for a new feature across tool vendors could be a reason if you have any concerns about working with multiple vendors.
Since the question is subjective, I'll express the contrary opinion.
If you work where there are code reviews, you'll find out soon enough what your co-workers consider "unfamiliar".
Since they also have to maintain the code, you can try and help them become familiar with the "unfamiliar" code. But, it's ultimately a judgment call, and sometimes, what you think is clear code, isn't.
i heard that these(say for example Groovy) languages have the capability of changing the variable name or call methods dynamically in runtime! What you meant by dynamic languages? And what is the real need for changing any values during runtime? Is that doen't lead to confusion, because at runtime if you change any value(or your programming constriants change anything), then whats the need for compilation(because it decides and confirms these values will be used, then there is no meaning of changing it in dynamically)? And i know there should be something useful, so only people have introduced these concepts!
I guess i'm clear about my question! And i need some brief explanation :)
Three points:
1) Yes, that is what is meant by 'dynamic languages' -- that you can add methods to a class at runtime is a common feature of dynamic languages (for example).
2) You bring up a good point that this ability could lead to confusing runtime issues. Proponents of dynamic languages would say the benefits of the feature outway the downsides. Being able to meta program can be very powerful.
3) compile time checks can still help in development with dynamic languages, if nothing more than for syntax checks. However, with dynamic languages, you do lose some of the compile time safety of non-dynamic languages. Note that some dynamic languages are interpreted (e.g. javascript) so its kind of a moot point.
Actually I am making a major project in implementing compiler optimization techniques. I already know about the existing techniques, but I am confused what technique to choose and how to implement it.
G'day,
What area of optimization are you talking about?
Compiler optimizations such as:
loop optimizations
dataflow optimizations
static single assignment based optimizations
code generator optimizations
etc.
etc.
Or optimization in the performance of the compiler itself, i.e. the speed with which it works?
Assuming that you have a compiler to optimize, and if it wasn't written by you, look up the documentation to see what is missing. Otherwise, if it was written by you, you can start off with the simplest. The definition for the simplest will depend on the language your compiler consumes. Or am I missing something?
I think you may have over optimized your question . Are you trying to decide where to start or trying to decide if some optimizations are worth implementing and others are not? I would assume all of the existing techniques have a place and are useful depending on the code they come across. If you are deciding which one to do first, pick the one you can do and do it. Pick the low hanging fruit. Get a few wins in your back pocket before you tackle a tough one and stumble and get frustrated. I would assume the real trick is having all the optimizations there and working but coming up with a way to decide which ones produce something better for a particular program and which ones get in the way and make things worse.
IMHO, the thing to do is implement the simple, obvious optimizations and then let it rest. Certainly it is very interesting to try to do weird and wonderful optimizations to rectify things that the user could simply have coded a little better, but if you really want to try to clean up after poor coding or poor design, the user can always outrun you. This is my favorite example.
My favorite example of compiler-optimizations-gone-nuts is Fortran compilers, where they go to such lengths to scramble code to shave a few hypothetical cycles that the code is almost impossible to debug, and typically the program counter is in there less than 1% of the time, so the effort is wasted.
After switching back and forth between several scripting languages this week, I found myself thinking how similar they all are. Yet I'm always reaching for Google (or nowadays SO) to remember details like what the local equivalents of "instanceof" and "endswith" are, or the right syntax to declare an interface, or whatever.
This reminded me of the (human) language Europonto. Just pick some vaguely English syntax and some vaguely Romance/Germanic/Slavic vocabulary, and it's all good!
So what would happen if we tried to do the same thing with a scripting language. In the mood for Python-style indented blocks today? Fine! Want to use a prototype object? Ok! Can only remember how to spell the PHP names of some library function? No problem!
Anyway, that's the wild and crazy idea. Since we need a question that admits concrete answers, let's tighten it up like this:
What would be the most significant conflicts in creating a scripting language that permitted all the native syntax and library functions of [Python, Ruby, PHP, Perl, shell, and JavaScript], such that you could freely intermix code blocks and function names between languages?
And let's say that any particular construction should be consistent at the statement level. So we'll allow:
foreach( $foo as $bar )
{
if $foo == 2:
print "hi"
}
but not, say,
foreach( $foo as $bar )
{
if $foo == 2:
print "hi"
endif
end
Conflicts can include: parser ambiguities; name collision; conflicting semantics for objects or functions or closures; etc. I'm guessing that scope will be a ginormous issue, but you tell me.
I'll start this as "community wiki" from the get go, so if you think it's a fun question but want to make it more rigorous, feel free to edit.
I would suggest that the main problem is recognising what the syntax of each statement is supposed to be.
In any case, what is the point? Almost all scripting languages have facilities to do much the same things, which is why people tend to master one that they use consistently, and stick with it.
The main difficulty would to be to allow people maintain it. With a well defined language you can only print a certain way and do sys.argv a certain way. once you allow multiple syntaxes there is no sane way to search for all the sys.argv in the code base you have.
At the syntactical level the only problem I can see would be to detect which block has which syntax, then separate them and parse them with specific parsers. Of course given very small statements there could be ambiguities as to which language it is and you could argue that it doesn't matter, but it just may be the case, that in different languages the same string of characters does different things so this could be a subtle issue.
At the API level you would have lots of different methods of doing the same thing but in a subtly different way or subset of doing it. So for example you could have no way of doing Java's string.startsWith() in let's say PHP, so you would do something different, or no way of doing PHP's strstr() (which returns a part of the string from the found needle to the end) and you would implement something different for that or even think differently about the problem. Then you would have to have all those different API methods of doing the same things and that would be huge API to implement, support and (god forbid) learn.
At the wetware level the code written by others would be totally unreadable unless you know a ton of languages and their subtle differences. I think it is difficult enough to learn a single programming language to the smallest details and so it is not practical at all to have this kind of frankensteinish beast created. I can think of an exception for use as an algorithm description language which it already is used in universities all over the world, where teacher takes some language of his liking and makes the code as readable as it can be for a human without needing to implement a parser for it.
As a side note I think this kind of system could be implemented at the least effort by somehow utilizing .NET's CLR where you have a ton of different languages each compiling to the same bytecode and accessing the same variables and stuff. All you'd need to do is split the code to clusters of different languages, then compile them separately on their respective compilers and then just merge the bytecode and somehow make sure they all point to the same variables and functions when mentioning the same names across the different languages.
I have begun to see that syntax is but one property of a language. And most of them look like C to me. The purpose of a language (object oriented, strong typing, etc) is something else again. It starts to look like syntax is not the most important aspect.
I went and read the wikipedia entry...
Europanto is a linguistic jest presented as a "constructed language" with a hodge-podge vocabulary
"Hodge-podge" sounds like the way Perl has been described to me!
I found a rather detailed discussion of closures in Ruby. It sounds like getting Ruby's behavior to coexist with JavaScript's or Python's would require some kind of ugly disambiguation.
If anybody were to add Perl to the list of languages to be covered, I think its lexical scoping rules would present a related problem?
There are a lot of discussions all over the internet and on SO, i.e. here and here, about static vs dynamic languages.
I'm not going to ask again about one vs another. Instead, my question is for those who moved (or at least tried to move) from static typed language to dynamic.
I'm not talking about moderate usage of JS on your web page or other scripting language embedded into statically typed software or small personal scripts. I mean moving to dynamic language as your primary general purpose language for developing production quality software in team.
Was that easy? What was the biggest advantage and the biggest challenge? Was it fun? :)
UPD: Did you find IDE support good enough? Did you find that you need less IDE support?
Was that easy?
Moderately. Some Java-isms are hard habits to break. My first six months, I wrote Python with ;'s. Icky. Once I was over it, though, I haven't looked back.
What was the biggest advantage?
Moving from the "write -> compile -> build -> run -> break -> debug -> write" cycle to a "write -> run -> break -> write" cycle. It takes time to get used to immediate gratification from the Python command-line interpreter. I was soooo used to endless design and planning before attempting to write (much less compile) any code.
At first I considered the python command line to be a kind of "education-only" interface. Then reading docstrings, doctests, and user guides where the application is being typed at the >>> prompt, I started to realize that the truly great Python software boils complexity and nuance down to stuff you can type interactively.
[I wish I could design stuff that worked that cleanly.]
What was the biggest challenge?
Multiple inheritance. I use it very rarely.
Was it fun?
So far.
It's also amazingly productive. More time with user requirements and real data. Less time planning an inheritance hierarchy with proper interfaces to capture meaning and compile correctly and be extensible enough to last at least to the next revision.
If I were you, I would try Scala!!!.
Scala has some aspects really interesting that lets you feel like doing dynamic, while doing static.
Scala is a statically typed language
with dynamic typed smell, because the
compiler makes you less repetitive
inferring your assignments.
A compiled language with a warm and
wonderful script flavor.Cause you can use the scala console, or even write scripts just like ruby or python. So you can choose between "write -> compile -> build -> run -> break -> debug -> write" or "write -> run -> break -> write" as S.Lott said.
Scala is a complete Functional
language with full support for OO. So you don't lose many important OO aspects like inheritance, encapsulation, polymorphism, etc.
Why answering you questions suggesting Scala? Because I tryed script languages before, and the main was Ruby. And it was just like S.Lott said. But not so easy for me and my team. Most of time static is safe, less error prone, and even faster if you have the right language.
Answering you three questions putting Scala inside we have:
Was that easy?
Yes. Sometimes you need to concentrate to leave you old concepts aside and go deep.
What was the biggest advantage?
You feel in home cause you don't need to change you environment or rewrite existing applications to migrate to Scala (talking about Java). If you come from Java, you can start playing with Scala after reading some articles. Not too much effort. Another important advantage is the use of a functional language en its embedded power.
Was it fun?
Sure! Changing your mind, changing your way to solve problems to the best is for sure funny.
This is my vision. You don't exactly need to leave off static to grab the advantage of dynamic.
Nice question.
I am now working in Ruby, PHP and ActionScript (the least dynamic of the three) instead of languages that I would prefer, like Java and C#. But beggars, I mean, workers in this economy, can't be choosers. Or rather, you have to choose your battles and your master.
It's hard to compare Ruby and Java because they've got more than one difference, and you only asked about the dynamic/static thing (and not even about the strongly vs. weakly-typed thing!). But on that front, what affects me most is always the IDE. I was always horrified when other Java programmers used Notepad or Textpad to write code, and nowadays there are just too many advantages of a good IDE for that madness. Not true with Ruby! I use Netbeans and it does really well, but one of the main differences is that I have to actually type code. Autocomplete, for me, was/is a way of life (I write SMS messages in full English/Spanish with the predictive dictionary, for instance, and never use abbreviations) and writing Ruby code does require more work.
So at first it was painful and I was constantly looking at, for instance, function names of classes that I had written (or that are part of Ruby) just to get the spelling right! So that sucked, I thought, and I continued to think that until...
I moved back to ActionScript the other day, and to get my IDE autocompleting (FlashDevelop or FlexBuilder) I declare all variables with types (strongly-typed by choice, if you will)... and suddenly I thought what a friggin' hassle!
And then today I had to do some feature additions on a Ruby project and it felt free and cool. The code is clean, and why would I be informing the IDE of what I'm trying to write anyway?
So I would say that 1) the biggest challenges are learning the language and the framework you're working in, like always 2) it's been amazingly fun and deeply eye-opening. New languages always carry new things with them, but dynamic languages just feel different. And that's just the kind of thing that gets you to wake up at 7am and do some coding on a Sunday morning before falling asleep again.
I like programming and like most of you, I've spent some time with stored procedures, XSL, static, dynamic, whatever... it's all fun, and they all feel totally different. In the end, the framework you are working in will be the thing that will convince you too stay or not (if you have a choice), I think, but languages are to learned, studied and experienced, not compared.
I can't qualify myself fully under that handle but I did spend a while writing some an interesting Python mini-game after having spent many years writing Java. So, I might be mixing a little bit of moving from compiled to interpreted along with it.
I found myself using notation to mimic static typing. :)
However, I did find myself cranking code out at a slightly better clip. Having an interpreter is a godsend as far as learning new language/writing new code. The shorter the time between finishing a line of code and seeing it work, the faster you can write, and I think that is probably the best thing most dynamic and interpreted languages.
My code didn't look too different, all things considered. Though, Python has a lot of fun data structures. :)
I'm also interested in this topic.
Tried do dive into Ruby and Rails a while ago, and it really helped me to grasp the ASP.Net MVC stuff, which i think is a bit too chalenging at first for average .net developer.
If you're interested more on moving in this direction, or curious about how some developers moved from static to dynamic languages as their full time jobs, i highly recommend this Alt.Net podcast.