Text.Megaparsec.Pos

Textual source position.

Documentation

data SourcePos

The abstract data type SourcePos represents source positions. It contains the name of the source (i.e. file name), a line number and a column number. SourcePos is an instance of the Show, Eq and Ord class.

Instances

Eq SourcePos

Ord SourcePos

Show SourcePos

sourceName :: SourcePos -> String

Extract the name of the source from a source position.

sourceLine :: SourcePos -> Int

Extract the line number from a source position.

sourceColumn :: SourcePos -> Int

Extract the column number from a source position.

data InvalidTextualPosition

This exception is thrown when some action on SourcePos is performed that would make column number or line number inside this data structure non-positive.

The InvalidTextualPosition structure includes in order:

• name of file
• line number (possibly non-positive value)
• column number (possibly non-positive value)

Constructors

InvalidTextualPosition String Int Int

Instances

Eq InvalidTextualPosition

Show InvalidTextualPosition

Exception InvalidTextualPosition

newPos

Arguments

:: String

File name

-> Int

Line number, minimum is 1

-> Int

Column number, minimum is 1

-> SourcePos

Create a new SourcePos with the given source name, line number and column number.

If line number of column number is not positive, InvalidTextualPosition will be thrown.

initialPos :: String -> SourcePos

Create a new SourcePos with the given source name, and line number and column number set to 1, the upper left.

incSourceLine :: SourcePos -> Int -> SourcePos

Increment the line number of a source position. If resulting line number is not positive, InvalidTextualPosition will be thrown.

incSourceColumn :: SourcePos -> Int -> SourcePos

Increment the column number of a source position. If resulting column number is not positive, InvalidTextualPosition will be thrown.

setSourceName :: SourcePos -> String -> SourcePos

Set the name of the source.

setSourceLine :: SourcePos -> Int -> SourcePos

Set the line number of a source position. If the line number is not positive, InvalidTextualPosition will be thrown.

setSourceColumn :: SourcePos -> Int -> SourcePos

Set the column number of a source position. If the line number is not positive, InvalidTextualPosition will be thrown.

updatePosChar

Arguments

:: Int

Tab width

-> SourcePos

Initial position

-> Char

Character at the position

-> SourcePos

Update a source position given a character. The first argument specifies tab width. If the character is a newline ('\n') the line number is incremented by 1. If the character is a tab ('\t') the column number is incremented to the nearest tab position, i.e. column + width - ((column - 1) `rem` width). In all other cases, the column is incremented by 1.

If given tab width is not positive, defaultTabWidth will be used.

updatePosString

Arguments

:: Int

Tab width

-> SourcePos

Initial position

-> String

String to process

-> SourcePos

The expression updatePosString pos s updates the source position pos by calling updatePosChar on every character in s, i.e.

updatePosString width = foldl (updatePosChar width)

defaultTabWidth :: Int

Value of tab width used by default. This is used as fall-back by updatePosChar and possibly in other cases. Always prefer this constant when you want to refer to default tab width because actual value may change in future. Current value is 8.