regex-tdfa-0.95.2: Replaces/Enhances Text.Regex




This Text.Regex.TDFA.Pattern module provides the Pattern data type and its subtypes. This Pattern type is used to represent the parsed form of a Regular Expression.



data Pattern Source

Pattern is the type returned by the regular expression parser. This is consumed by the CorePattern module and the tender leaves are nibbled by the TNFA module.


type GroupIndex = IntSource

GroupIndex is for indexing submatches from capturing parenthesized groups (PGroup/Group)

newtype DoPa Source

Used to track elements of the pattern that accept characters or are anchors




dopaIndex :: Int


showPattern :: Pattern -> StringSource

I have not been checking, but this should have the property that parsing the resulting string should result in an identical Pattern. This is not true if starTrans has created PNonCapture and PNonEmpty values or a (PStar False). The contents of a [ ] grouping are always shown in a sorted canonical order.

Internal use

starTrans :: Pattern -> PatternSource

Do the transformation and simplification in a single traversal. This removes the PPlus PQuest and PBound values for POr and PEmpty and PStar True/False. For some PBound values it creates PNonEmpty and PNonCapture. It also simplifies to flatten out nested POr and PConcat instances and elimiate some uneeded PEmpty values.

Internal use, Operations to support debugging under ghci

simplify' :: Pattern -> PatternSource

Function to transform a pattern into an equivalent, but less redundant form. Nested POr and PConcat are flattened.



:: (Pattern -> Pattern)

The transformation function

-> Pattern

The Pattern to transform

-> Pattern

The transformed Pattern

Apply a Pattern transfomation function depth first