Clojurians Log v2

hey all. from http://braveclojure.com exercises, I'm trying to write mapset which works like map but returns a set. I'm struggling with getting it to work for more than one collection argument

(defn mapset
  "map but returns set"
  [func & colls]
  (set (map func colls)))

(mapset inc [1 1 1 2] [2 2 2 3]) gives me > ; class clojure.lang.PersistentVector cannot be cast to class java.lang.Number

(defn mapset
   "map but returns set"
   [func & colls]
   (set (apply map func colls)))

Also (map inc [1 2] [3 4]) will fail because only a single number can be incremented.

So maybe (mapset + [1 1 1 2] [2 2 2 3])

brilliant, thank you!

super neato

I'm taking a windows file path as an argument (i.e. "C:\Program Files") and feeding it to http://java.io/file. I get an error because of special characters in the string. What's the idiomatic way to escape those chars?

"C:\\Program Files" probably

but in Java this also works on Windows I think:

C:/Program Files

Can someone help me fix this Spec please? I’m trying to check if something is a valid arousal level, which must be between 0 and 1 (s/def arousal-level? (s/or #(< 0 %) #(> 1 %))) Unexpected error (AssertionError) macroexpanding s/or at (src/anxiety_loop/core.clj:1:166). Assert failed: spec/or expects k1 p1 k2 p2..., where ks are keywords (c/and (even? (count key-pred-forms)) (every? keyword? keys))

That’s a really good error message. S/or expects k1 p1 where the k’s are keywords.

Yeah I guess every condition has a keyword to identify it

So you would have (s/or :cond-1 #(< 0 %) :cond-2 #(> 1 %))

This is useful eg. when you call s/conform on a value, for it can let you know which condition was satisfied

Also once you understand what’s going on, you can remove the need for the s/or with (< 0 % 1)

Does s/def work on a symbol like that? Specs are usually registered as a keyword in a central registry

Oh that’s cool I forgot that’s how that works

But solve it with the or so you understand what’s going on. And then simplify

s/def can take both keywords and symbols, but they have to be fully namespace qualified. Look at res in clojure.spec.alpha

here it is a def so just the spec

the mouth of the crocodile has to look to the other sie @rob370

<

Calling int on the boolean seems strange

The value 101 satisfies pos? , so it 'passes' the spec (specs are not best thought of as predicates, though, rather as descriptions of the shape of data). What you want is to use s/and instead of s/or when your value has to satisfies all conditions, ie. both be positive and less than 100. In this case you can get away with using a single function:`(s/def ::arousal-level #(< 0 % 100))`

(def arousal-level (s/and pos?
                          int?
                          #(> 100 %)))

Thank you for the help everyone

There is actually a function pos-int? in the standard library, I discovered just now.

It’s great that you solved your problem but It’s still weird that you use > instead of < !

They are checking for an integer less than 100, which (> 100 %) does

function specs are registered with symbols so this is allowed (but is not what was intended)

Thanks @borkdude! Is there a function that will escape special characters for me?

specs absolutely are best thought of as predicates describing value sets