Clojure

Support arbitrary functional destructuring via -> and ->>

Details

  • Type: Enhancement Enhancement
  • Status: In Progress In Progress
  • Priority: Minor Minor
  • Resolution: Unresolved
  • Affects Version/s: None
  • Fix Version/s: Approved Backlog
  • Component/s: None
  • Labels:
    None
  • Approval:
    Incomplete

Description

Support arbitrary functional destructuring, that is the use of
any function in any destructuring form to help unpack data in
arbitrary ways.

The discussion began here:
http://clojure-log.n01se.net/date/2009-11-17.html#09:31c

The attached patch implements the spec described here:
http://clojure-log.n01se.net/date/2009-11-17.html#10:50a

That is, the following examples would now work:

user=> (let [(-> str a) 1] a)
"1"

user=> (let [[a (-> str b) c] [1 2]] (list a b c))
(1 "2" nil)

user=> (let [(->> (map int) [a b]) "ab"] (list a b))
(97 98)

Activity

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Assembla Importer added a comment -

chouser@n01se.net said: [file:aHWQ_W06Kr3O89eJe5afGb]: [PATCH] Support -> and ->> in destructuring forms.

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Assembla Importer added a comment - chouser@n01se.net said: [file:aHWQ_W06Kr3O89eJe5afGb]: [PATCH] Support -> and ->> in destructuring forms.
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Assembla Importer added a comment -

cgrand said: I think the current patch suffers from the problem described here http://groups.google.com/group/clojure-dev/msg/80ba7fad2ff04708 too.

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Assembla Importer added a comment - cgrand said: I think the current patch suffers from the problem described here http://groups.google.com/group/clojure-dev/msg/80ba7fad2ff04708 too.
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Assembla Importer added a comment -

richhickey said: so, don't use syntax-quote, just use clojure.core/->

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Assembla Importer added a comment - richhickey said: so, don't use syntax-quote, just use clojure.core/->
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Assembla Importer added a comment -

chouser@n01se.net said: Only -> and ->> are actually legal here anyway – if you've locally bound foo to -> there's not really any good reason to think (fn [(foo inc a)] a) should work. And if you've redefined -> or ->> to mean something else in your ns, do we need to catch that at compile time, or is it okay to emit the rearranged code and see what happens?

In short, would '#{> ->> clojure.core/> clojure.core/->>} be sufficient?

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Assembla Importer added a comment - chouser@n01se.net said: Only -> and ->> are actually legal here anyway – if you've locally bound foo to -> there's not really any good reason to think (fn [(foo inc a)] a) should work. And if you've redefined -> or ->> to mean something else in your ns, do we need to catch that at compile time, or is it okay to emit the rearranged code and see what happens? In short, would '#{> ->> clojure.core/> clojure.core/->>} be sufficient?
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Assembla Importer added a comment -

cgrand said: Only -> and ->> are legal here but what if they are aliased or shadowed? Instead of testing the symboil per se I would check, if:

  • the symbol is not in &env
  • the symbol resolve to #'clojure.core/> or #'clojure.core/>>
(when-not (&env (first b)) (#{#'clojure.core/-> #'clojure.core/->>} (resolve (first b))))

but it requires to change destructure's sig to pass the env around

Show
Assembla Importer added a comment - cgrand said: Only -> and ->> are legal here but what if they are aliased or shadowed? Instead of testing the symboil per se I would check, if:
  • the symbol is not in &env
  • the symbol resolve to #'clojure.core/> or #'clojure.core/>>
(when-not (&env (first b)) (#{#'clojure.core/-> #'clojure.core/->>} (resolve (first b))))
but it requires to change destructure's sig to pass the env around
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Stuart Halloway added a comment -

Rich: Are you assigned to this by accident? If so, please deassign yourself.

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Stuart Halloway added a comment - Rich: Are you assigned to this by accident? If so, please deassign yourself.
Stuart Halloway made changes -
Field Original Value New Value
Reporter Assembla Importer [ importer ]
Priority Minor [ 4 ]
Approval Test Incomplete
Waiting On richhickey
Rich Hickey made changes -
Assignee Rich Hickey [ richhickey ]
Waiting On richhickey
Alexander Redington made changes -
Fix Version/s Approved Backlog [ 10034 ]
Fix Version/s Release.Next [ 10038 ]

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Dates

  • Created:
    Updated:
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