2010/11/24 Mike Meyer <mwm-keyword-googlegroups.620...@mired.org>
> On Wed, 24 Nov 2010 00:37:07 -0800 (PST)
> LauJensen <lau.jen...@bestinclass.dk> wrote:
>
> You just touched on an idiom I see fairly often here that bugs me. I'm
> not intentionally singling you - or CQL! - out for this, but you made
> a comment that sets up my question perfectly.
>
> > (let [photo-counts (-> (table :photos)
> > (aggregate [[:count/* :as :cnt]] [:id])))]
> > (-> (table :users)
> > (join photo-counts (= {:users.id :photos.id}))
> >
> > I think thats really as simple as you can express that join operation.
>
> Um, I can see two macros that, if expanded in place, would result in a
> simpler expression (assuming that CQL doesn't redefine ->):
>
> (let [photo-counts (aggregate (table :photos) [[:count/* :as :cnt]] [:id])]
> (join (table :users) photo-counts (= {:users.id :photos.id})))
>
> I also fixed the parens - I think. I removed one after [:id], and it
> seems like two were missing at the end as well.
>
> Ok, I understand why you would use -> if you're threading through
> multiple forms. I don't know that I like it, but I can at least
> understand it. But when it's only one form? In the best case - when
> the form is a symbol, as in (-> 1 inc) - it just wastes three
> characters to reverse the form and argument. More often - for example
> (-> 1 (+ 2)) - it also adds another level of parenthesis, which I
> thought most people considered a hindrance to comprehension.
>
> Could someone explain where this urge to write (-> expr (func arg))
> instead of (func expr arg) comes from?
>
Maybe the lack of refactoring tools: expressions starting big, then some
pieces are refactored out, but not totally ?
I know my code looks like this sometimes, and I have to go back to it to
remove these remaining (-> a b).
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