Welcome! There is a whole channel dedicated to the clojure ecosystem in vscode at #vscode

And you'll find folks in the #beginners channel are very very helpful as you're learning!

General use

As the docstrings for add-tap suggests, remember the function (instance, not the var) if you want to be able to remove it later. No remove-all now.

Usually, you’ll be using add-tap interactively while logging / debugging so this is either trivial or unneeded

Well, disagree

Tap is very simple. I’m not sure whether a “guide” is worth doing

And prepl is designed for tool-makers, not something most people will be using directly

Both have docstrings with a bunch of additional info

Will think about what enhanced docs are useful before GA

I think it’s good to have at least a useful example of when and how to use tap

Makes one wonder: why prepl isn't a separate lib? I guess we aren't seeing the whole picture yet, might it be part of future plans?

yes, tap and prepl are largely latent capabilities, laying the groundwork for other things in the future.

prepl is not a separate lib for the same reason the socket server stuff is not a separate lib (and tap is in core) - so that when you need to open up a remoteable debugging repl connection, everything is already there - you don’t need to rebuild your uber jar or redeploy or whatever

like asked on Apropos (youtube), is there a reason there’s only one global tapset?

@U04V15CAJ presumably because it's intended primarily for debugging?

Can you give an example of how this helps for debugging? In the place where you normally invoke a function like println, swap! to some debug atom, etc. you now invoke tap?

what is tap?

Let's stop tip tapping around the issue, someone should write a blog post 😛

Here is how I understood what is tap

1. tap is global accessable debuging port 2. it is possible to register any number of functions with 1 arg to process values from tap port. In order to register fn we can use add-tap function 3. tap> is non blocking fn that puts any value to a tap port. All registered functions will receive values from tap

4. functions which process values from tap can be pure or not. If fn is not pure iti is recommended to run I/O in separate thread (I think taht core.async rules here make sense)

@U064X3EF3 is this more or less correct?

@U097654L8 I understand how it works, but not when and why you should use it instead of putting debug lines in a function

@U04V15CAJ But what if you want to catch a bug which appears under some special conditions? Then you need to catch a data, that causes a bug and some context from app. Your code may be deployed on several servers in the cloud and app can produce millions of logs. I think tap + prepl is out of the box tool, that can help in this situation. Using tap + prepl you can avoid grep logs on remote servers, you can send data with a bug (not all logs) from multiple servers right to your notebook repl. Then you can discover what's wrong with your code, patch it and then using prepl send it back to app to see if bug is still there or not.

you can use tap as an alternative to doing println debugging or logging to understand what is happening in your system

it is useful like println in that it’s in core so you don’t need to change the requires in your code when you add it (and unlike logging which typically drags in a bunch of junk when you do so)

it’s different and likely better than println or logging in that tap transfers data values, not strings

Is this also a better alternative to storing values in some temporary atom for later inspection? I guess you could do that in one of the tap functions

it’s better than println debugging in that it does not rely on you having *out* go someplace visible - you can independently hook up one or more taps that can get it to your eyes in whatever way is appropriate in your system

@U04V15CAJ I don’t know if I’d say better - it’s a different tool. saving values off is possibly more useful if you are repl-connected

I always have a repl connected 🙂

and to earlier question @U04V15CAJ - there’s one global tapset because that’s simpler. otherwise you’re building full pub/sub. You can get that if you want by writing tagged tap values and connecting a function that makes choices about what to do based on the tags

but most people don’t need that and will never need to take that on

I guess you would have to think before hand to put tap calls where you would previously add logging, so not having a REPL means redeploying your code somewhere. I don’t see the full potential of this yet

because tap drops by default, it’s totally fine to put them in beforehand

you can dynamically add the tap later

(which you can’t do with println)

yeah, but like with logging, you wish you had logged somewhere where you didn’t usually 😉

but that’s cool, just add a tap in case and hook some tap-fn later on… but then you still would need a REPL I guess

but unlike logging, you don’t have to drag the logger crap into your code (as tap> is in core)

unless you proactively have a tap-fn that responds to something you can do dynamically

but that is very system dependent

on macosx there is the say terminal command. E.g $ say "hello world"

the best ones I've seen use the Google Translate engine, e.g. http://soundoftext.com or the Read Aloud plugin for Chrome

my fault. it was a bug in clojure 1.7 works with 1.9