search

functional-koans / clojure-koans

A set of exercises for learning Clojure
3.74k stars 2.14k forks source link

Replace all triple underscores '___' with double '__'. #148

Closed equwal closed 5 years ago

equwal commented 5 years ago

May as well be consistent and use the same double underscore everywhere. This consistency could make it easier to write code in the future which relies on it, and is just nicer I think.

trptcolin commented 5 years ago

I'm not sure about this, because they're different values under the hood: __ is :fill-in-the-blank and ___ is a function that returns that value.

I see why it looks appealing - right now, the effect is the same when running lein koan run. But I think that's because the error reporting kind of swallows the stack trace when the __ function (the keyword) is passed any number of arguments except 1 or 2. I don't necessarily want to tie too tightly to the current error reporting, and I want things to basically make sense when people work in the REPL.

Here's an example of what I mean. For each of the below cases, I'm comparing the existing behavior of ___ to the behavior of __.

koan-engine.runner=> (((fn [] ___)) 4 5)
:fill-in-the-blank
koan-engine.runner=> (((fn [] __)) 4 5)
5
koan-engine.runner=> ((fn [f] (f 4 5)) ___)
:fill-in-the-blank
koan-engine.runner=> ((fn [f] (f 4 5)) __)
5
koan-engine.runner=> (___ (fn [n] (* n n)))
:fill-in-the-blank
koan-engine.runner=> (__ (fn [n] (* n n)))
nil
koan-engine.runner=> (defn square [n] (* n n))
#'koan-engine.runner/square
koan-engine.runner=> (___ square)
:fill-in-the-blank
koan-engine.runner=> (__ square)
nil

I much prefer the :fill-in-the-blank behavior for these, and think that explaining the behavior of __ in these cases is going to be more confusing as folks work through it on their own to find that keywords can act as functions of 1 or 2 arguments, returning nil when the lookup finds nothing. So I'm going to close this one, but thanks for the effort!

Also, minor side note for next time - lein koan test helps us make sure things keep working. This PR fails lein koan test, but it's for mundane reasons instead of finding the stuff I described above - the structure of resources/koans.clj fills in all the __ and ___ in order, so this one failed because the ___ answers didn't get used.

equwal commented 5 years ago

Thanks for taking the time to go through this. I wasn't using lein koan to run the koans, I was just compiling each file as I went along in my IDE.