A set of non-overlapping, non-abutting Spans

You may also think of an Area like a span that can be empty or have “gaps.”

Construct and combine areas using mempty, spanArea, fromTo, +, and -.

Construct a contiguous Area consisting of a single Span specified by two Locs

The lesser loc will be the start, and the greater loc will be the end. If the two locs are equal, the area will be empty.

Construct an Area consisting of a single Span

>>> spanArea (read "4:5-6:3")
[4:5-6:3]

The union of two Areas

Spans that overlap or abut will be merged in the result.

>>> read "[1:1-1:2]" + mempty
[1:1-1:2]

>>> read "[1:1-1:2]" + read "[1:2-1:3]"
[1:1-1:3]

>>> read "[1:1-1:2]" + read "[1:1-3:1]"
[1:1-3:1]

>>> read "[1:1-1:2]" + read "[1:1-11:1]"
[1:1-11:1]

>>> read "[1:1-3:1,6:1-6:2]" + read "[1:1-6:1]"
[1:1-6:2]

>>> read "[1:1-3:1]" + read "[5:1-6:2]"
[1:1-3:1,5:1-6:2]

The difference between two Areas

a - b contains what is covered by a and not covered by b.

addSpan s a is the union of Area a and Span s

>>> addSpan (read "1:1-6:1") (read "[1:1-3:1,6:1-6:2]")
[1:1-6:2]

The first contiguous Span in the Area, or Nothing if the area is empty

>>> firstSpan mempty
Nothing

>>> firstSpan (read "[3:4-7:2]")
Just 3:4-7:2

>>> firstSpan (read "[3:4-7:2,15:6-17:9]")
Just 3:4-7:2

The last contiguous Span in the Area, or Nothing if the area is empty

>>> lastSpan mempty
Nothing

>>> lastSpan (read "[3:4-7:2]")
Just 3:4-7:2

>>> lastSpan (read "[3:4-7:2,15:6-17:9]")
Just 15:6-17:9

The Loc at which the Area starts, or Nothing if the Area is empty

>>> start mempty
Nothing

>>> start (read "[3:4-7:2]")
Just 3:4

>>> start (read "[3:4-7:2,15:6-17:9]")
Just 3:4

The Loc at which the Area ends, or Nothing if the Area is empty

>>> end mempty
Nothing

>>> end (read "[3:4-7:2]")
Just 7:2

>>> end (read "[3:4-7:2,15:6-17:9]")
Just 17:9

A Span from start to end, or Nothing if the Area is empty

>>> areaSpan mempty
Nothing

>>> areaSpan (read "[3:4-7:2]")
Just 3:4-7:2

>>> areaSpan (read "[3:4-7:2,15:6-17:9]")
Just 3:4-17:9

A list of the Spans that constitute an Area, sorted in ascending order

>>> spansAsc mempty
[]

>>> spansAsc (read "[3:4-7:2,15:6-17:9]")
[3:4-7:2,15:6-17:9]

>>> spanCount mempty
0

>>> spanCount (read "[3:4-7:2]")
1

>>> spanCount (read "[3:4-7:2,15:6-17:9]")
2

>>> readPrec_to_S areaReadPrec minPrec "[]"
[([],"")]

>>> readPrec_to_S areaReadPrec minPrec "[3:2-5:5,8:3-11:4]"
[([3:2-5:5,8:3-11:4],"")]

>>> readPrec_to_S areaReadPrec minPrec "[3:2-5:5,11:4-8:3]"
[([3:2-5:5,8:3-11:4],"")]

>>> readPrec_to_S areaReadPrec minPrec "[3:2-5:5,8:3-8:3]"
[]