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[CLJ-1074] Read/print round-trip for +/-Infinity and NaN Created: 21/Sep/12  Updated: 12/Feb/15

Status: Open
Project: Clojure
Component/s: None
Affects Version/s: Release 1.4
Fix Version/s: None

Type: Defect Priority: Minor
Reporter: Colin Jones Assignee: Unassigned
Resolution: Unresolved Votes: 5
Labels: print, reader

Attachments: Text File 0001-Read-Infinity-and-NaN.patch     Text File clj-1074-read-infinity-and-nan-patch-v2-plus-edn-reader.patch    
Patch: Code and Test
Approval: Triaged

 Description   

A few float-related forms (namely, Double/POSITIVE_INFINITY, Double/NEGATIVE_INFINITY, Double/NaN) are not eval-able after a round-trip via

(read-string (binding [*print-dup* true] (pr-str f))

The two options I see are to provide print-method implementations for these and their Float cousins, or to make Infinity, -Infinity, +Infinity, and NaN readable values. Since it sounds like edn may want to provide a spec for these values (see https://groups.google.com/d/topic/clojure-dev/LeJpOhHxESs/discussion and https://github.com/edn-format/edn/issues/2), I think making these values directly readable as already printed is preferable. Something like Double/POSITIVE_INFINITY seems too low-level from edn's perspective, as it would refer to a Java class and constant.

I'm attaching a patch implementing reader support for Infinity, -Infinity, +Infinity, and NaN.



 Comments   
Comment by Timothy Baldridge [ 03/Dec/12 11:34 AM ]

Please bring this up on clojure-dev. We'll be able to vet this ticket after that.

Comment by Colin Jones [ 03/Dec/12 1:18 PM ]

Should I respond to my original clojure-dev post about this (linked in the issue description above), or start a new one?

Comment by Andy Fingerhut [ 24/May/13 1:11 PM ]

Patch clj-1074-read-infinity-and-nan-patch-v2.txt dated May 24 2013 is identical to 0001-Read-Infinity-and-NaN.patch dated Sep 21 2012, except it applies cleanly to latest master. The older patch conflicts with a recent commit made for CLJ-873.

Comment by Nicola Mometto [ 25/May/13 11:55 AM ]

clj-1074-read-infinity-and-nan-patch-v2-plus-edn-reader.patch is the same as clj-1074-read-infinity-and-nan-patch-v2.txt except it patches EdnReader too, but it must be applied after #CLJ-873 0001-Fix-CLJ-873-for-EdnReader-too.patch get merged

Comment by Andrew Tarzwell [ 12/Feb/15 12:01 PM ]

We're running into this bug now, applying the patch clj-1074-read-infinity-and-nan-patch-v2-plus-edn-reader.patch seems to resolve it on 1.7 master, but it would be an improvement to not depend on a patched version.

Is there a fix in the works? Or a more up to date conversation on why this hasn't been addressed?

Thanks,
Andrew

Comment by Andy Fingerhut [ 12/Feb/15 12:23 PM ]

Andrew, the tools.reader library provides this enhancement today, if you would prefer using unpatched software, and if it meets your needs. There are a few other small differences between it and the reader built into Clojure, which you can see near the end of its README: https://github.com/clojure/tools.reader

As far as why it hasn't been addressed yet, I think a short accurate answer is that the Clojure developers have been working on other issues, and this one has not been high enough priority to be addressed yet (disclaimer: This is in no way an official answer, just the best guess of an observer who watches this stuff too much).

I see you have voted on the ticket. Good. More votes can in some cases influence the Clojure developers to respond to a ticket earlier rather than later. You may try to persuade others to vote on it, too, if you wish.

If there is some production use of Clojure hindered by the lack of a fix, bringing this up in the Clojure or Clojure Dev Google groups couldn't hurt (signed CA on file required for Clojure Dev group membership – see http://clojure.org/contributing )

Comment by Andrew Tarzwell [ 12/Feb/15 1:46 PM ]

Andy,

Thank you for the quick response, I was unaware of tools.reader having this fixed. That should do us for now.

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