A wrapper around Text for fast line/column navigation. Concatenation takes linear time.

This is a building block for Rope, which provides logarithmic concatenation.

Create from Text, linear time.

Extract Text, O(1).

Check whether a text is empty, O(1).

Split into lines by \n, similar to Data.Text.lines. Each line is produced in O(1).

>>> :set -XOverloadedStrings
>>> lines ""
[]
>>> lines "foo"
["foo"]
>>> lines "foo\n"
["foo"]
>>> lines "foo\n\n"
["foo",""]
>>> lines "foo\nbar"
["foo","bar"]

Equivalent to length . lines, but in O(1).

>>> :set -XOverloadedStrings
>>> lengthInLines ""
0
>>> lengthInLines "foo"
1
>>> lengthInLines "foo\n"
1
>>> lengthInLines "foo\n\n"
2
>>> lengthInLines "foo\nbar"
2

Split at given line, O(1).

>>> :set -XOverloadedStrings
>>> map (\l -> splitAtLine l "foo\nbar") [0..3]
[("","foo\nbar"),("foo\n","bar"),("foo\nbar",""),("foo\nbar","")]

Length in UTF-16 code units. Takes linear time.

>>> :set -XOverloadedStrings
>>> length "fя𐀀"
4
>>> Data.Text.Lines.length "fя𐀀"
3

Split at given UTF-16 code unit. If requested number of code units splits a code point in half, return Nothing. Takes linear time.

>>> :set -XOverloadedStrings
>>> map (\c -> splitAt c "fя𐀀") [0..4]
[Just ("","fя𐀀"),Just ("f","я𐀀"),Just ("fя","𐀀"),Nothing,Just ("fя𐀀","")]

Represent a position in a text.

Measure text length as an amount of lines and columns. Time is proportional to the length of the last line.

>>> :set -XOverloadedStrings
>>> lengthAsPosition "f𐀀"
Position {posLine = 0, posColumn = 3}
>>> lengthAsPosition "f\n𐀀"
Position {posLine = 1, posColumn = 2}
>>> lengthAsPosition "f\n𐀀\n"
Position {posLine = 2, posColumn = 0}

Combination of splitAtLine and subsequent splitAt. If requested number of code units splits a code point in half, return Nothing. Time is linear in posColumn, but does not depend on posLine.

>>> :set -XOverloadedStrings
>>> splitAtPosition (Position 1 0) "f\n𐀀я"
Just ("f\n","𐀀я")
>>> splitAtPosition (Position 1 1) "f\n𐀀я"
Nothing
>>> splitAtPosition (Position 1 2) "f\n𐀀я"
Just ("f\n𐀀","я")
>>> splitAtPosition (Position 0 2) "f\n𐀀я"
Just ("f\n","𐀀я")
>>> splitAtPosition (Position 0 3) "f\n𐀀я"
Nothing
>>> splitAtPosition (Position 0 4) "f\n𐀀я"
Just ("f\n𐀀","я")