Text.Pandoc.Walk

Functions for manipulating Pandoc documents or extracting information from them by walking the Pandoc structure (or intermediate structures like '[Block]' or '[Inline]'. These are faster (by a factor of four or five) than the generic functions defined in Text.Pandoc.Generic.

Here's a simple example, defining a function that replaces all the level 3+ headers in a document with regular paragraphs in ALL CAPS:

import Text.Pandoc.Definition
import Text.Pandoc.Walk
import Data.Char (toUpper)

modHeader :: Block -> Block
modHeader (Header n _ xs) | n >= 3 = Para $ walk allCaps xs
modHeader x = x

allCaps :: Inline -> Inline
allCaps (Str xs) = Str $ map toUpper xs
allCaps x = x

changeHeaders :: Pandoc -> Pandoc
changeHeaders = walk modHeader

query can be used, for example, to compile a list of URLs linked to in a document:

extractURL :: Inline -> [String]
extractURL (Link _ _ (u,_)) = [u]
extractURL (Image _ _ (u,_)) = [u]
extractURL _ = []

extractURLs :: Pandoc -> [String]
extractURLs = query extractURL

Documentation

class Walkable a b where

Methods

walk :: (a -> a) -> b -> b

walk f x walks the structure x (bottom up) and replaces every occurrence of an a with the result of applying f to it.

walkM :: (Monad m, Functor m) => (a -> m a) -> b -> m b

A monadic version of walk.

query :: Monoid c => (a -> c) -> b -> c

query f x walks the structure x (bottom up) and applies f to every a, appending the results.

Instances

Walkable Inline Citation

Walkable Inline Inline

Walkable Inline Block

Walkable Inline MetaValue

Walkable Inline Meta

Walkable Inline Pandoc

Walkable Block Citation

Walkable Block Inline

Walkable Block Block

Walkable Block MetaValue

Walkable Block Meta

Walkable Block Pandoc

Walkable Meta Meta

Walkable Pandoc Pandoc

(Foldable t, Traversable t, Walkable a b) => Walkable a (t b)

(Walkable a b, Walkable a c) => Walkable a (b, c)