On 30/10/13 16:56, P Martin wrote:
Thanks - I'm still a little confused on the different between use and
require.
'use' is sort of deprecated after it was noticed that people were
abusing it. It's not exactly deprecated because in some cases like
incremental development at the repl it is really usefyl to have. That
said, 'require' can do everything 'use' can via " :refer :all". so what
I'm saying is the the following two are equivalent :
(require '[clojure.tools.macro :refer :all])
(use '[clojure.tools.macro])
Now, in perhaps 8/10 cases you should not do any of that. The next guy
that will look at your code will not have the slightest clue what
external fns you're using. He literally has to manually inspect the
entirity of that external namespace and figure out which ones you've
actually used. A more informative way would be the following 2:
(require '[clojure.tools.macro :as mac]) ;;if you're unsure of what you
'll end up using just alias it
(require '[clojure.tools.macro :refer [name-with-attributes mexpand-all
]]) ;;if you know upfront what you need, specify it
using the second you don't need an alias, but you've explicitly said
"here are the only vars i've used". Massive difference don't you agree?
In the case of var-clash due to same name, just make sure you use
aliases. That is if you want both vars with the same name. If you don't
just overwrite the one or :exclude it via:
(:refer-clojure :exclude [==]) ;;core.logic does this all the time
When I try your suggestion for the matrix library, (require
'(clojure.core.matrix :as mat)), I get:
IllegalArgumentException Don't know how to create ISeq from:
clojure.lang.Keyword clojure.lang.RT.seqFrom (RT.java:505)
I'm really sorry about that...I'm pretty sure that works in a
ns-declaration, I'm puzzled as to why it doesn't work here. In any case,
a quoted vector (as shown above) does work just fine. It also looks nicer :)
hope that helps,
Jim
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