Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Not Lisp again (2009)

funcall.blogspot.com

Post reply on HN
Print view View original

91–100 of 276 posts

Re: Not Lisp again (2009)

#91

Post by conistonwater »

vog wrote: post #49
ungzd wrote: post #32

Earlier quoted context omitted.

Better example would be symbolic differentiation[1][2] which requires more quirks even in modern languages[3][4] [1] https://mitpress.mit.edu/sicp/full-text/sicp/book/node39.htm... [2] https://github.com/clojure-numerics/expresso [3] http://docs.sympy.org/latest/tutorial/intro.html#a-more-inte... [4] https://github.com/yuemingl/SymJava#examples

Note that the simplistic approach doesn't scale well, as terms tend to "explode" in size and hence computation time. There is a whole sub field of mathematics / computer science called "algorithmic differentiation", also known as "automatic differentiation". The goal is to take an existing computer program and transform it into another computer program that calculates the derivatice just as efficiently (up to a const…

It doesn't stop at forward-mode, and reverse-mode, because finding the optimal mode relates to a complicated graph problem, which, IIRC, is NP-hard in general. Not only that, but most of the difficulty is in getting these tools to work on arbitrary codebases, making it more a software engineering problem rather than a maths problem.

Re: Not Lisp again (2009)

#92

Post by phailhaus »

AnimalMuppet wrote: post #79
jlongster wrote: post #52

Earlier quoted context omitted.

That's not really the same thing at all. What's missing is the ability to close over values, which is a key part of first-class functions. You could not re-create the original example in C, which is to return a new function. You'd have to return some sort of object that keeps a reference to the function pointer, and provides a special mechanism for calling it, i.e. a poor man's closure.

OK, for the example given , I don't see how closures are relevant. I could write the exact same derivative function in C in 1983. Are you saying that in general , closures are essential to first-class functions? Or are you saying that, in the derivative example, there's something going on with closures?

Are you sure? Because in the example given, it seems that the inner function needs access to the function f

Re: Not Lisp again (2009)

#93

Post by klibertp »

emsy wrote: post #17
pmoriarty wrote: post #6

The objections the author had way back in the day are no longer the objections programmers of mainstream languages have to Lisp today. Today the objections I hear are more along the lines of: 1 - All those parenthesis. (Still a top objection) 2 - Lisp doesn't look like or work like what I'm used to. 3 - Lisp doesn't have as many libraries as the most popular mainstream programming languages. 4 - There aren't nearly a…

For me it's not the paranthesis, but that Lisp posts always show low level code. At least half of my programming is tying together high level services and libraries. I know how I can express those concepts succinctly in Java, C++, JS, Swift etc. I'd love to see some examples of Lisp for something like a REST controller, where I call services, repositories etc.

> I'd love to see some examples of Lisp for something like a REST controller, where I call services, repositories etc.

Not exactly what you're looking for, but take a look at my post: https://klibert.pl/posts/racket_quickie.html

It shows a little JSON-based REST service which stores a list of messages and allows listing them and adding to them. With more URLs you'd likely use something like this: http://docs.racket-lang.org/web-server/dispatch.html for dispatch, instead of hand-coded function.

It's notable for only using stdlib, no additional packages (beyond purely syntactic, Clojure-like, `~>` support).

To be honest, the APIs exposed in the stdlib feel kind of awkward - like using SimpleHTTPServer in Python. Still, it's just a couple of lines and easy (automatic, in this example) in-process concurrency is not bad.

Re: Not Lisp again (2009)

#94

Post by crimsonalucard »

nine_k wrote: post #66
crimsonalucard wrote: post #27

Earlier quoted context omitted.

Learning lisp or functional programming is more of a conceptual experience than a practical one. That is not to say it is not practical to learn lisp, but the state of the programming world as it is today makes it so that it is less practical to learn lisp than it is to learn about say something like java.

If you ever have to write JavaScript, a fairly practical and widespread language, the functional paradigm proves to be highly useful.

I have used javascript extensively. I can tell you the functional paradigm is almost NEVER used in javascript. Javascript just contains libraries, features and concepts brought over from functional programming but I have never seen anyone program javascript functionally..

If a single one of your functions in javascript contains more than one imperative procedure you have exited the functional paradigm.

Re: Not Lisp again (2009)

#95

Post by mnarayan01 »

BoiledCabbage wrote: post #37
c3534l wrote: post #14

Yeah, but it's goddamned ugly and unreadable. It considers repetition to be a design feature . If you're going to sell people on the benefits of functional programming, I think you should really be pushing more for SML or Haskell or something like that.

It's been stated a number of times, but x.f(y, z) has just as many parens as (f x y z). And Haskell particularly comes with so many syntax quirks. There is a lot of cruft you need to learn to get to the underlying functional core of haskell. Lips you can get 100% of the cruft out within a few days / 1 week. And the rest is just understanding programming concepts. I don't use any LISP on a regular basis, but it still…

  x + y * z
has way fewer than

  (+ x (* y z))
though. I'm not arguing for one or the other, but e.g. infix operators do have upsides.

Re: Not Lisp again (2009)

#96

Post by klibertp »

chimeracoder wrote: post #88
emsy wrote: post #17

Earlier quoted context omitted.

For me it's not the paranthesis, but that Lisp posts always show low level code. At least half of my programming is tying together high level services and libraries. I know how I can express those concepts succinctly in Java, C++, JS, Swift etc. I'd love to see some examples of Lisp for something like a REST controller, where I call services, repositories etc.

> At least half of my programming is tying together high level services and libraries. I know how I can express those concepts succinctly in Java, C++, JS, Swift etc. I'd love to see some examples of Lisp for something like a REST controller, where I call services, repositories etc. You should look at Racket. Racket is a Scheme-like[0] Lisp that aims to be "batteries-included". It includes things like a web-server ou…

> whether it is really "a Scheme" or not

It's not and it's not about being pedantic. Racket changed its name nearly a decade ago and, at that point, it already wasn't Scheme either.

I have a post about where Racket (and Clojure) come from: https://klibert.pl/posts/clojure_and_racket_history.html

Re: Not Lisp again (2009)

#97

Post by tromp »

chirau wrote: post #38
tromp wrote: post #30

Earlier quoted context omitted.

Lisp has the minimal syntax for lists: (a b c d) where other languages require separating commas, but Haskell has minimal syntax for function application: f x y z with no parenthesis needed. (Technically, this is a triple application ((f x) y) z, masked by the convention of application being a left-associative binary operator.)

How would you write f((x y)z) in Haskell?

f (x y z)

Re: Not Lisp again (2009)

#99

Post by vq »

chirau wrote: post #38
tromp wrote: post #30

Earlier quoted context omitted.

Lisp has the minimal syntax for lists: (a b c d) where other languages require separating commas, but Haskell has minimal syntax for function application: f x y z with no parenthesis needed. (Technically, this is a triple application ((f x) y) z, masked by the convention of application being a left-associative binary operator.)

How would you write f((x y)z) in Haskell?

If by (x y) you mean x(y) then I would write it like this:

f (x y) z

Re: Not Lisp again (2009)

#100

Post by cygned »

emsy wrote: post #17
pmoriarty wrote: post #6

The objections the author had way back in the day are no longer the objections programmers of mainstream languages have to Lisp today. Today the objections I hear are more along the lines of: 1 - All those parenthesis. (Still a top objection) 2 - Lisp doesn't look like or work like what I'm used to. 3 - Lisp doesn't have as many libraries as the most popular mainstream programming languages. 4 - There aren't nearly a…

For me it's not the paranthesis, but that Lisp posts always show low level code. At least half of my programming is tying together high level services and libraries. I know how I can express those concepts succinctly in Java, C++, JS, Swift etc. I'd love to see some examples of Lisp for something like a REST controller, where I call services, repositories etc.

I have written an example web application for my cloud computing lecture. The code is not pretty nor 100% functionally and there are some bugs, but it shows how my applications work. It's just for demonstration purposes and therefore kept simple.

https://github.com/dak0rn/Zwitscher

Feel free to shout me questions or remarks.

Edit: Here's a simple endpoint that uses a service which then works with the database;

https://github.com/dak0rn/Zwitscher/blob/master/src/zwitsche...

Post reply on HN