Opened 7 years ago

Closed 7 years ago

Last modified 6 years ago

#996 closed proposal (wontfix)

Add ranged sets

Reported by: pauljohnson Owned by:
Priority: normal Milestone:
Component: libraries/base Version: 6.6
Keywords: Cc:
Operating System: Unknown/Multiple Architecture: Unknown/Multiple
Type of failure: Difficulty: Unknown
Test Case: Blocked By:
Blocking: Related Tickets:

Description

Ranged sets represent sets of ordered values as lists of ranges. Each range has a lower and
upper boundary, and for any value and boundary the value is either above or below the boundary:
no value can ever sit on a boundary. There are also boundaries for +/- infinity (BoundaryBelowAll? and BoundaryAboveAll?).

The upshot is that you can represent a set of reals such as

[ 2.0 < x <= 3.4, 6.7 < x]

or a couple of encyclopedia volumes as:

<= x < "blob", "goo" <= x < "hun"?

The usual set operators are provided. The library also does the Right Thing with adjacent values:

[2 < x <= 3] Union [4 <= x < 5] == [2 < x < 5]

[2.0 < x <= 3.0] Union [4.0 <= x < 5.0] == [2.0 < x <= 3.0, 4.0 <= x < 5.0]

I've needed something like this more than once over the years, in various languages. Haskell
is the first one that can actually do the Right Thing efficiently for a polymorphic type.

The source contains Haddock comments and a comprehensive set of QuickCheck? properties. I've integrated these into the documentation. So far I've tested this on GHC 6.4.1, although this patch is against the HEAD of the current libraries.

If this patch is accepted I'll also add patches for ranged sets of times (e.g. the set of all times within the first Tuesday of each month), and to filter finite maps against ranged sets.

Attachments (1)

test.txt (78.4 KB) - added by pauljohnson 7 years ago.

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Change History (5)

Changed 7 years ago by pauljohnson

comment:1 Changed 7 years ago by simonmar

Is there a good reason this has to be in base rather than in a separate package?

comment:2 Changed 7 years ago by ross

  • Resolution set to wontfix
  • Status changed from new to closed

This should be a separate package.

comment:3 Changed 6 years ago by simonmar

  • Architecture changed from Unknown to Unknown/Multiple

comment:4 Changed 6 years ago by simonmar

  • Operating System changed from Unknown to Unknown/Multiple
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