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

Minimal complete definition

walk, walkM, query

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

Methods

walk :: (Inline -> Inline) -> Citation -> Citation

walkM :: (Monad m, Functor m) => (Inline -> m Inline) -> Citation -> m Citation

query :: Monoid c => (Inline -> c) -> Citation -> c

Walkable Inline Inline

Methods

walk :: (Inline -> Inline) -> Inline -> Inline

walkM :: (Monad m, Functor m) => (Inline -> m Inline) -> Inline -> m Inline

query :: Monoid c => (Inline -> c) -> Inline -> c

Walkable Inline Block

Methods

walk :: (Inline -> Inline) -> Block -> Block

walkM :: (Monad m, Functor m) => (Inline -> m Inline) -> Block -> m Block

query :: Monoid c => (Inline -> c) -> Block -> c

Walkable Inline MetaValue

Methods

walk :: (Inline -> Inline) -> MetaValue -> MetaValue

walkM :: (Monad m, Functor m) => (Inline -> m Inline) -> MetaValue -> m MetaValue

query :: Monoid c => (Inline -> c) -> MetaValue -> c

Walkable Inline Meta

Methods

walk :: (Inline -> Inline) -> Meta -> Meta

walkM :: (Monad m, Functor m) => (Inline -> m Inline) -> Meta -> m Meta

query :: Monoid c => (Inline -> c) -> Meta -> c

Walkable Inline Pandoc

Methods

walk :: (Inline -> Inline) -> Pandoc -> Pandoc

walkM :: (Monad m, Functor m) => (Inline -> m Inline) -> Pandoc -> m Pandoc

query :: Monoid c => (Inline -> c) -> Pandoc -> c

Walkable Block Citation

Methods

walk :: (Block -> Block) -> Citation -> Citation

walkM :: (Monad m, Functor m) => (Block -> m Block) -> Citation -> m Citation

query :: Monoid c => (Block -> c) -> Citation -> c

Walkable Block Inline

Methods

walk :: (Block -> Block) -> Inline -> Inline

walkM :: (Monad m, Functor m) => (Block -> m Block) -> Inline -> m Inline

query :: Monoid c => (Block -> c) -> Inline -> c

Walkable Block Block

Methods

walk :: (Block -> Block) -> Block -> Block

walkM :: (Monad m, Functor m) => (Block -> m Block) -> Block -> m Block

query :: Monoid c => (Block -> c) -> Block -> c

Walkable Block MetaValue

Methods

walk :: (Block -> Block) -> MetaValue -> MetaValue

walkM :: (Monad m, Functor m) => (Block -> m Block) -> MetaValue -> m MetaValue

query :: Monoid c => (Block -> c) -> MetaValue -> c

Walkable Block Meta

Methods

walk :: (Block -> Block) -> Meta -> Meta

walkM :: (Monad m, Functor m) => (Block -> m Block) -> Meta -> m Meta

query :: Monoid c => (Block -> c) -> Meta -> c

Walkable Block Pandoc

Methods

walk :: (Block -> Block) -> Pandoc -> Pandoc

walkM :: (Monad m, Functor m) => (Block -> m Block) -> Pandoc -> m Pandoc

query :: Monoid c => (Block -> c) -> Pandoc -> c

Walkable Meta Meta

Methods

walk :: (Meta -> Meta) -> Meta -> Meta

walkM :: (Monad m, Functor m) => (Meta -> m Meta) -> Meta -> m Meta

query :: Monoid c => (Meta -> c) -> Meta -> c

Walkable Pandoc Pandoc

Methods

walk :: (Pandoc -> Pandoc) -> Pandoc -> Pandoc

walkM :: (Monad m, Functor m) => (Pandoc -> m Pandoc) -> Pandoc -> m Pandoc

query :: Monoid c => (Pandoc -> c) -> Pandoc -> c

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

Methods

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

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

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

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

Methods

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

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

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