5 ms·

Pun: A small library to enable pattern matching in JavaScript and CoffeeScript

73 points by unignorant 12y ago

jlongster 12y ago
Very cool! You might also want to check out sparkler, which uses macros to let you do this with a little better syntax: https://github.com/natefaubion/sparkler https://github.com/natefaubion/sparkler
- unignorant 12y ago
  I'd heard of sparkler, but my impression was that macros prevent it from working with CoffeeScript. There's also matches.js, which is the deprecated precursor to sparkler: https://github.com/natefaubion/matches.js https://github.com/natefaubion/matches.js
ilaksh 12y ago
Very awesome. Also see LiveScript http://livescript.net/ http://livescript.net/
d0m 12y ago
What I'd like is a small library to complement lodash/underscore with utility functions required when using high-level ones. It's very annoying to have verbose _.each([1,2,3], function(x) { something(x, 'param'); } when it could be _.each([1,2,3], $.call(something, _, 'param')) It seems like the current solution is to use _.pluck() or similar functions for common use-cases, or use _.partial which I find even more verbose than standard functions. e.g. _.map(objs, $.pluck('person.age')) promise.then($.ret(some_fn, _, 'a')) promise.then(some_fn) doesn't work because what we want is to return some_fn from within a function. promise.then(function(x) { return some_fn(x, 'a'); }) I know there are ways around, but those are not unified in a standard and coherent library that could complement other high-level libraries.
- kaonashi 12y ago
  Recently watched this video, which describes why underscore is actually making this difficult through its design. https://www.youtube.com/watch?v=m3svKOdZijA https://www.youtube.com/watch?v=m3svKOdZijA
  - goldenkey 12y ago
    That was a great talk! Thank you. Started out a bit hanky because of his nervousness but he pulled through and ramped up.
- rjn945 12y ago
  Happily, you're first example is actually already supported in the latest Underscore (1.6.0): _.each([1,2,3], _.partial(something, _, 'param')) Example: _.map([1, 2, 3, 4], _.partial(Math.pow, _, 8)) // [1, 256, 6561, 65536] Admittedly, "_.partial" is 3 more characters than "$.call", but if you really used it a lot, you could alias it to something short like "_p". Unfortunately, this doesn't seem to be present in the latest Lo-Dash (which I generally prefer).
- klibertp 12y ago
  Use LiveScript. No, seriously, LiveScript is great and I used it in production already, without any problems. Your first example would look like this in LS: _.each [1 to 3], (something _, 'param') where "_" in this context means partial application. Even better, LS has special syntax for accessing an object method and binding it at the same time, this is a bit of code I wrote recently: httpify-promise = (promise) -> # add `success` and `error` methods to the promise, making it into # $http-compatible one promise with success: (promise~then _, null) error: (promise~then null, _) Now this is really beautiful and powerful. I also played with promises some time ago, in Node, where I used q library and LiveScript. Partial application and curried functions from prelude-ls let me write code like this: read-dir(directory) .then map (path.join directory, _) .then get-stats .then tee (collect-files-into accum) .then filter (at 1) .then walk-subdirs .thenResolve accum (the whole file here: http://klibert.pl/walkfiles.html http://klibert.pl/walkfiles.html) In short, having support for many higher-level idioms as part of a language, as opposed to library, makes it MUCH more pleasant to work with.
  - agumonkey 12y ago
    That tee + thenResolve pattern is a first for me. Is this from LS or did they take it from another lang/lib ?
    - klibertp 12y ago
      It's actually a very little function I wrote, based on `tee` Unix shell command: http://unixhelp.ed.ac.uk/CGI/man-cgi?tee http://unixhelp.ed.ac.uk/CGI/man-cgi?tee It looks like this: tee = (func, val) --> func(val); val which could be equivalently written as: tee = (func) -> (val) -> func(val); val In other words it's an identity function which additionally executes some other function for side-effects. In the shell the `tee` command always writes to the file, while my version can execute any side-effect, but I think my version is just a generalization of the standard Unix command and so I named it like this. I'm sure this function has its own, formal name, with the word "monad" or "combinator" (maybe K combinator?) in it, but I wasn't patient enough to research it :) `thenResolve` is a standard method on a promise object implemented by the Q library (https://github.com/kriskowal/q/wiki/API-Reference#promisethenresolvevalue https://github.com/kriskowal/q/wiki/API-Reference#promisethe...) I used, it's equivalent to .then () -> accum In other words, `thenResolve` appends a success callback which discards previous value and always returns another value. Once again, take a look at the full source at http://klibert.pl/walkfiles.html http://klibert.pl/walkfiles.html - I'm going to update it with a full explanation of what's going on, but even right now it's only 90 lines with including comments, and should be a good example of main LS strengths. I'm probably going to write another example which makes use of even more (and more advanced) LS features when I'm done with explaining this one.
elwell 12y ago
I love this kind of stuff.
tkubacki 12y ago
Every time I see things like this I'm grateful for Dart SDK
andybak 12y ago
A quick comparison of some Python implementations I found via quick Googling: https://gist.github.com/andybak/45e3155420d18420a34a https://gist.github.com/andybak/45e3155420d18420a34a
- unignorant 12y ago
  Nice, that's a clever use of decorators. A bit annoying that you need repeated "defs", though. Here's another approach based on Macropy (basically, macros for Python): https://github.com/lihaoyi/macropy#pattern-matching https://github.com/lihaoyi/macropy#pattern-matching.
rubiquity 12y ago
This is cool but I would love if these features were implemented at compile time instead of using functions. Great work either way!

73 points by unignorant 12y ago

Very cool! You might also want to check out sparkler, which uses macros to let you do this with a little better syntax: https://github.com/natefaubion/sparkler https://github.com/natefaubion/sparkler

unignorant 12y ago
I'd heard of sparkler, but my impression was that macros prevent it from working with CoffeeScript. There's also matches.js, which is the deprecated precursor to sparkler: https://github.com/natefaubion/matches.js https://github.com/natefaubion/matches.js

ilaksh 12y ago

Very awesome. Also see LiveScript http://livescript.net/ http://livescript.net/

d0m 12y ago

What I'd like is a small library to complement lodash/underscore with utility functions required when using high-level ones. It's very annoying to have verbose _.each([1,2,3], function(x) { something(x, 'param'); } when it could be _.each([1,2,3], $.call(something, _, 'param')) It seems like the current solution is to use _.pluck() or similar functions for common use-cases, or use _.partial which I find even more verbose than standard functions. e.g. _.map(objs, $.pluck('person.age')) promise.then($.ret(some_fn, _, 'a')) promise.then(some_fn) doesn't work because what we want is to return some_fn from within a function. promise.then(function(x) { return some_fn(x, 'a'); }) I know there are ways around, but those are not unified in a standard and coherent library that could complement other high-level libraries.

kaonashi 12y ago
Recently watched this video, which describes why underscore is actually making this difficult through its design. https://www.youtube.com/watch?v=m3svKOdZijA https://www.youtube.com/watch?v=m3svKOdZijA
- goldenkey 12y ago
  That was a great talk! Thank you. Started out a bit hanky because of his nervousness but he pulled through and ramped up.
rjn945 12y ago
Happily, you're first example is actually already supported in the latest Underscore (1.6.0): _.each([1,2,3], _.partial(something, _, 'param')) Example: _.map([1, 2, 3, 4], _.partial(Math.pow, _, 8)) // [1, 256, 6561, 65536] Admittedly, "_.partial" is 3 more characters than "$.call", but if you really used it a lot, you could alias it to something short like "_p". Unfortunately, this doesn't seem to be present in the latest Lo-Dash (which I generally prefer).
klibertp 12y ago
Use LiveScript. No, seriously, LiveScript is great and I used it in production already, without any problems. Your first example would look like this in LS: _.each [1 to 3], (something _, 'param') where "_" in this context means partial application. Even better, LS has special syntax for accessing an object method and binding it at the same time, this is a bit of code I wrote recently: httpify-promise = (promise) -> # add `success` and `error` methods to the promise, making it into # $http-compatible one promise with success: (promise~then _, null) error: (promise~then null, _) Now this is really beautiful and powerful. I also played with promises some time ago, in Node, where I used q library and LiveScript. Partial application and curried functions from prelude-ls let me write code like this: read-dir(directory) .then map (path.join directory, _) .then get-stats .then tee (collect-files-into accum) .then filter (at 1) .then walk-subdirs .thenResolve accum (the whole file here: http://klibert.pl/walkfiles.html http://klibert.pl/walkfiles.html) In short, having support for many higher-level idioms as part of a language, as opposed to library, makes it MUCH more pleasant to work with.
- agumonkey 12y ago
  That tee + thenResolve pattern is a first for me. Is this from LS or did they take it from another lang/lib ?
  - klibertp 12y ago
    It's actually a very little function I wrote, based on `tee` Unix shell command: http://unixhelp.ed.ac.uk/CGI/man-cgi?tee http://unixhelp.ed.ac.uk/CGI/man-cgi?tee It looks like this: tee = (func, val) --> func(val); val which could be equivalently written as: tee = (func) -> (val) -> func(val); val In other words it's an identity function which additionally executes some other function for side-effects. In the shell the `tee` command always writes to the file, while my version can execute any side-effect, but I think my version is just a generalization of the standard Unix command and so I named it like this. I'm sure this function has its own, formal name, with the word "monad" or "combinator" (maybe K combinator?) in it, but I wasn't patient enough to research it :) `thenResolve` is a standard method on a promise object implemented by the Q library (https://github.com/kriskowal/q/wiki/API-Reference#promisethenresolvevalue https://github.com/kriskowal/q/wiki/API-Reference#promisethe...) I used, it's equivalent to .then () -> accum In other words, `thenResolve` appends a success callback which discards previous value and always returns another value. Once again, take a look at the full source at http://klibert.pl/walkfiles.html http://klibert.pl/walkfiles.html - I'm going to update it with a full explanation of what's going on, but even right now it's only 90 lines with including comments, and should be a good example of main LS strengths. I'm probably going to write another example which makes use of even more (and more advanced) LS features when I'm done with explaining this one.

elwell 12y ago

I love this kind of stuff.

tkubacki 12y ago

Every time I see things like this I'm grateful for Dart SDK

andybak 12y ago

A quick comparison of some Python implementations I found via quick Googling: https://gist.github.com/andybak/45e3155420d18420a34a https://gist.github.com/andybak/45e3155420d18420a34a

unignorant 12y ago
Nice, that's a clever use of decorators. A bit annoying that you need repeated "defs", though. Here's another approach based on Macropy (basically, macros for Python): https://github.com/lihaoyi/macropy#pattern-matching https://github.com/lihaoyi/macropy#pattern-matching.

rubiquity 12y ago

This is cool but I would love if these features were implemented at compile time instead of using functions. Great work either way!