If-statements in Smalltalk (2008)
pozorvlak.livejournal.com
pozorvlak.livejournal.com
a < b:
ifTrue: [...]
ifFalse: [...]
Coming from Pascal and C, seeing that IF/ELSE could be implement without special syntax was a real mind warper.
You may be able to build web applications too (http://seaside.st/).
Then again, we live in the era of Docker, in which it's commonplace to ship an entire Linux filesystem along with your web app. So shipping a Smalltalk VM (2.6MB for Pharo 5.0) shouldn't be too much of a stretch.
10 timesRepeat: [ n := n*2 ].
[ n < 10 ] whileTrue: [ n := n + 1 ] 10.times { n = n * 2 }
class Proc
def whileTrue; yield while self.call; end
end
# And use:
n = 1
->{ n < 10 }.whileTrue { n = n + 1 }
puts n
E.g. suppose you want to build up an AST of the statement
(x < 0) ifTrue:[-x] ifFalse:[x]
As an sexp:
(ASTIfStatement
:condition (ASTLessThan #1=(ASTVariable :name x) (ASTConstant :value 0))
:consequent (ASTUnaryMinus #1#)
:alternative #1#)
r.table('users').filter(lambda user:
user["age"] == 30
).run(conn)
You can indeed accomplish some similar things with it.
> Does it have performance disadvantages?
A Common Lisp macro is evaluated once at compile time. In Smalltalk this is evaluated at runtime, so that adds some overhead. Usually you only have to build the AST only once though, and can use the result many times, so that overhead isn't really relevant.
Integer::> aNumber
^x adaptToInteger: self andCompare: #<
But, for all the fangled cool things that the more powerful languages of yesteryears (like lisp), what seems to actually precipitate adoption is simply history, not necessarily expressiveness/powerful abstractions, etc. See C, sh and friends, javascript. Arguably, python is one where its ease made it popular and it continues to develop language wise, albeit not without controversy.
Currently about 7K lines into a python project and I'm getting more used to it but 'leaky abstractions' is a term that springs to mind at least 10 times per day if not more.
I'm busy with tricky array type conversions to feed stuff from one library into another a lot more than I would expect. Rather than that there is 'one way to do it' it seems there are about 50 of them, all incompatible with each other. Very messy at times.
My last statement referred to with python 3 and above, there is active development of the language's fundamental constructs. I guess there is active ES6 etc. C's newer standards aren't groundshakingly different from its original implementation.
Now hold on. The most successful sprog of nature is humanity[citation needed] and we're a case study in the fact that raw intelligence is more effective than fitness for any particular niche. So: as in nature, there may be a bunch of niche languages, but in time they'll find themselves with a conservation status while a smart language rules the earth.
Now, this is an important observation, but it needs one caveat - "fittest for its environment" != "fittest for the stated purpose". I.e. an objectively better tool may lose to a tool that's barely good enough, but e.g. provides a better CYA for managers, in a self-reinforcing loop of popularity.
That's the essence of Worse is Better - shit that's barely good enough will outcompete proper solutions.
(For many, that essay seems to be an ideal to follow; for me personally, it's just the description of the sad state of reality that we need to learn to work around.)
true = \x.\y.x
false = \x.\y.y
Declarative statements are a pattern in ruby - you see them everywhere (`attr_accessor`). They're library code - you're intended to write them. I can't imagine trying to write ruby without that pattern, and I can't imagine them not being a design pattern.
Similarly - the MVC of Rails. The lines get way fuzzier, but you still might try to draw similar lines to separate the core framework (badly analogous to the language) from, I guess, all the gems you end up using (badly analogous to the library). Is MVC a pattern? Or under this bad analogy, a language construct...?
attr_accessor, as it happens (http://ruby-doc.org/core-2.0.0/Module.html#method-i-attr_acc...) is implemented in C code, but one could implement it in Ruby, so I'd count it as part of the (standard) library, and creating accessors is just using a library method. In, say, Java setters and getters have to be written by hand (or autogenerated by some external system like an IDE), so they're a pattern. On the other hand, the way Ruby translates `foo.bar = 3` into a call to `foo`'s `bar=` method is not alterable by user code, so it's part of the language.
MVC in Rails is an interesting case. You have to create new classes according to the pattern (either by hand or using `rails generate`), but there's also some library support in the form of Model and Controller classes you're expected to inherit from, and which handle much of the View/Controller plumbing for you. I'd say it's still a pattern, though.
Yeah - I heard your point when I first read your post, but it took some more time and reading to understand it. It's a good distinction.
What I'm not getting is... So you've got a really precise and elegant line between "language" and "library", but it's not clear what the difference is between patterns and.... maybe idioms?
attr_accessor, has_many, and carrierwave's mount_uploader (to provide many examples) are all examples of a "pattern" (in the sense of a repeated thing, not a design pattern) in Ruby, but I can't determine what's then in need of "fixing" or what abstraction features could be added to remove the "pattern".
You missed the "created: 3246 days ago" bit, then? :-) But you're right that I don't spend much time here - thanks for the welcome!
> it's not clear what the difference is between patterns and.... maybe idioms?
You're right, it's not a clear distinction. But for our purposes, the important point about design patterns is "must be reimplemented from scratch for each use". Have you read the Gang of Four book? Their patterns all require the programmer to define a bunch of new classes from scratch each time the pattern is used. Compare the Decorator pattern (https://en.wikipedia.org/wiki/Decorator_pattern) to Python's decorators - the pattern requires the programmer to create new classes, forward methods, etc, but the Python feature requires the programmer to write one line of code (which then does all the class-creation and method-forwarding under the hood). The Python feature has successfully obviated the need for the pattern. You still need to write the same amount of application-specific business-logic code, but the machine handles all the tedious plumbing for you. Similarly, attr_accessor and has_many handle the tedious plumbing of getters/setters and collections-backed-by-join-queries, respectively. So the necessary abstraction features have already been added, and there's nothing left to fix. An interesting intermediate case is the Iterator pattern in Python (https://en.wikipedia.org/wiki/Iterator_pattern). Python still has explicit iterators, but standardises the interface so library code can make use of user-provided iterators. It also provides a convenient language-level facility for building iterators, using generator syntax. Haskell, arguably, has entirely absorbed iterators into the language, replacing them with lazy lists.
It's worth noting that the key property of Ruby that allows for things like attr_accessor is the ability to add methods and fields to an object or class at runtime, and thus to do so programmatically. Lisp can similarly dispense with a lot of patterns that are necessary in Java, because Lisp has compile-time code generation in the form of macros. Peter Norvig's talk on this is great: http://norvig.com/design-patterns/ppframe.htm
Tots did. Errr... welcome, travelling from the land of Lurk?
> You're right, it's not a clear distinction...
Still, does the naming sound right? Patterns that get "encoded" into the language, or made trivial by abstraction features within the language, are idioms?
> Have you read the Gang of Four book?
No :/ The closest I've come, weirdly, was tutoring a friend through a design pattern class. Each time she'd come up and say, "The name of this week's pattern is such-and-such", and from that, I'd get 90% of the way to knowing that pattern was. I've always wanted just a simple list of the names, maybe with linked single paragraph descriptions, but every prior time I've looked I haven't been able to find one.
> add methods and fields to an object or class at runtime
Yes! That's a favorite Ruby trick. Straight up tho - what is the formal name of doing that, specifically, the formal name of the category to which attr_accessor and has_many belong to?
Yeah, that sounds like a reasonable term to use.
> The closest I've come, weirdly, was tutoring a friend through a design pattern class.
It's a bit old now, but I think it's probably still worth reading the GoF book - it's clearly written, and much better than most subsequent imitators. In particular, each pattern comes with a "when not to use this" discussion, that more people should pay attention to :-/
> I've always wanted just a simple list of the names, maybe with linked single paragraph descriptions
Would http://wiki.c2.com/?CategoryPattern do?
> what is the formal name of doing that, specifically, the formal name of the category to which attr_accessor and has_many belong to?
I'm not sure. Adding methods to a class at runtime is called "metaprogramming" (which has the more general meaning of "writing code that writes or modifies code"). I don't know of a name for a method that performs metaprogramming, though.
Including an if message that looks like if in C or similar language and and unless construct that looks like Ruby.
On the other hand, it's possible to make (core language + standard library) too small. A particularly bad thing to leave out is a module/separate compilation system, ensuring that a zoo of incompatible module systems will grow up.
You may enjoy Guy Steele's talk "Growing a Language": https://www.youtube.com/watch?v=_ahvzDzKdB0
French speaking but PDFs are in english.
I mentioned the date because it is traditional in titles. Here it might put comparisons to ES9 and complaints about display on the iPhone 10s in context (I'm optimistic). Pessimistically, it might give fair warning that hyperlinks from the page 404.