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Problems

  • Many programs need to manipulate time-related values and we have no way to incorporate them in the data format used by read.
  • Different representations are commonplace and necessary.
  • The Java classes in this area are bad

Non-problems

  • there are no good libraries in this area, we need to invent one
    • Joda
Objectives
  • Provide reader support for time
  • Must be pluggable
    • Dictate only print/read format
  • Don't dictate return data type
  • print is already pluggable

Proposal

  • #@ISO8601-STRING reader macro
    • codename, swear-date
  • calls pluggable parser fn
    • extension point is via bindable var
  • default parser returns j.u.Date
    • provide optional parser for Joda and auto-install if detected?
  • print j.u.Dates (and Joda stuff) in this format

Issues

  • would be nice to return something meaningful given time part only
  • JDK 5 has no ISO8601 parser
    • JDK 6 has only in  javax.xml.bind.DatatypeConverter
  • Using Joda for parse introduces dep into Clojure
  • Print/read veracity requires matching parsers
    • is this a real issue?
    • is flexibility allowing difference not a feature?
  • Others I'm sure



Old Notes

Goal for an instant literal:

RH - this presumes an instant literal is a goal, it is not necessarily so

Provide a relatively easy way to create a human readable time instant.  Also provide a protocol based library of date functions

What this is:

  • A Reader Macro
  • Complies with ISO8601
  • Joda is the gold standard for parsing.  Specifically, the formatter returned by org.joda.time.format.ISODateTimeFormat/dateTime
  • Aware of offset from UTC
  • Provides a Dateable Protocol
  • Provides a CljDate type, which is aware of both the UTC instant and offset from UTC
    • Equality/Hashcode based on instant
    • Display based on instant+offset
  • Plays nice w/ Joda, includes docs to extend to Joda.
  • A collection of very common comparators and predicates.
  • A collection of converter functions
  • Written in Clojure, w/ exception of reader assignment

What this is NOT:

  • Time Zone support
  • Multiple Chonology support
  • Clever duration support
  • Directly dependent upon Joda
  • A PITA to use

Things to read to facilitate intelligent discussion (TO DO):

Known issues/things to solve

  • Support for only a date or time of day?
  • Allow partial composition in a literal?
  • Parsing dates before 1970 (Epoch start)
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