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| -rw-r--r-- | web/site.hs | 2 | ||||
| -rw-r--r-- | web/tutorials/05-arrows.markdown | 223 | ||||
| -rw-r--r-- | web/tutorials/06-guide.markdown | 129 | ||||
| -rw-r--r-- | web/tutorials/guide.markdown | 99 |
4 files changed, 100 insertions, 353 deletions
diff --git a/web/site.hs b/web/site.hs index f8b3794..6130bea 100644 --- a/web/site.hs +++ b/web/site.hs @@ -67,5 +67,5 @@ config :: Configuration config = defaultConfiguration { verbosity = Debug , deployCommand = "rsync --checksum -ave 'ssh -p 2222' \ - \_site/* jaspervdj@jaspervdj.be:jaspervdj.be/hakyll" + \_site/* jaspervdj@jaspervdj.be:jaspervdj.be/tmp/hakyll4" } diff --git a/web/tutorials/05-arrows.markdown b/web/tutorials/05-arrows.markdown deleted file mode 100644 index 3f2e244..0000000 --- a/web/tutorials/05-arrows.markdown +++ /dev/null @@ -1,223 +0,0 @@ ---- -title: Arrow Magic: Metadata Dependent Page Generation -author: Florian Hars ---- - -## Supporting a "published: false" attribute on pages - -Many content management systems or blog platforms support -some kind of workflow that display articles differently or -not at all depending on which state the article is in, for -example whether it has a "published" attribute or not. -Hakyll has no built-in support for anything like this, but since -its compilers are just arrows, it is easy to implement arbitrary -metadata dependent behaviour for rendering pages. - -Let's start by adding support for a "published" attributes to the -`simpleblog` example. We want to consider a blog post published if it -has a `published` metadata element that does not have the value -`false`. A function to test for this is simple: - -~~~~~{.haskell} -isPublished :: Page a -> Bool -isPublished p = - let published = getField "published" p in - published /= "" && published /= "false" -~~~~~ - -The next step is to write a function that tags a page with its -published status, which can be either unpublished or published, using -the standard `Either` datatype and then transform this function -into a `Compiler`. The latter can be done with the standard `arr` -function from `Control.Arrow`, which lifts a function into an arrow: - -~~~~~{.haskell} -isPagePublished :: Compiler (Page a) (Either (Page a) (Page a)) -isPagePublished = arr (\p -> if isPublished p then Right p else Left p) -~~~~~ - -For the next processing steps we now need a compiler that takes an -`Either (Page a) (Page a)` instead of the usual `Page a` as an -input. But the former can be built up from the latter using some -standard combinators from the `Control.Arrow` library. The simplest -one is `|||`, which takes two compilers (arrows) with the same output -type and returns a new compiler that takes an `Either` of the input -types of the Compilers as an input. Maybe we just want to render our -unpublished posts with a big warning that they are provisional, so we -just want to render the unpublished `Left` pages with another template -than the published `Right` pages: - -~~~~~{.haskell} - match "posts/*" $ do - route $ setExtension ".html" - compile $ pageCompiler - >>> isPagePublished - >>> (applyTemplateCompiler "templates/embargo-post.html" - ||| applyTemplateCompiler "templates/post.html") - >>> applyTemplateCompiler "templates/default.html" - >>> relativizeUrlsCompiler -~~~~~ - -With the conditional rendering in place, the next step is to hide -the unpublished posts from the homepage and the list of posts. -Both lists are generated from the results of a requireAllA call. -The last argument of requireAllA is a Compiler, and requireAllA -passes a pair consisting of the currently rendered page and a list -of all the required pages. All we have to do to suppress the pages -is to write a Compiler that takes such a pair as input, leaves the -first element of the pair unchanged and filters out all the unpublished -pages from list in the second element of the pair and then pass the -output from this compiler to the existing compilers handling the -list generation for the `index` and `posts` pages. - -Again, we can use a function from `Control.Arrow` to build this -compiler from simpler ones, in this case it is `***`, which combines -two arrows to one arrow from pairs to pairs. For our purposes, we -combine the identity arrow, which leaves its input unchanged, and an -ordinary `filter` on a list lifted into the compiler arrow: - -~~~~~{.haskell} -filterPublished :: Compiler (Page a, [Page b]) (Page a, [Page b]) -filterPublished = id *** arr (filter isPublished) -~~~~~ - -All that remains to do is to chain this compiler in front of the existing -compilers passed to requireAllA in the code for `posts.html` - -~~~~~{.haskell} - >>> requireAllA "posts/*" (filterPublished >>> addPostList) -~~~~~ - -and for `index.html`: - -~~~~~{.haskell} - >>> requireAllA "posts/*" - (filterPublished - >>> (id *** arr (take 3 . reverse . sortByBaseName)) - >>> addPostList) -~~~~~ - -You may have noticed that the code for the index page uses the same -`id *** something` construct to extract some elements from the list -of all posts. - -## Don't generate unpublished pages at all - -The above code will treat unpublished posts differently and hide them -from all lists of posts, but they will still be generated, and someone -who knows their URLs will still be able to access them. That may be -what you need, but sometimes you might want to suppress them -completely. The simplest way to do so is to leave the rendering -pipeline for `"posts/*"` unchanged and just add the `isPagePublished` -compiler at the end. This will not compile, since hakyll knows how to -write a `Page String`, but not how to write an `Either (Page String) -(Page String)`. But that can be amended by a simple type class -declaration: - -~~~~~{.haskell} -instance Writable b => Writable (Either a b) where - write p (Right b) = write p b - write _ _ = return () -~~~~~ - -Now hakyll will happily generate published pages and ignore -unpublished ones. This solution is of course slightly wasteful, as at -will apply all the templates to an unpublished page before finally -discarding it. You can avoid this by using the `+++` function, which -does for the sum datatype `Either` what `***` does for the product -type pair: - -~~~~~{.haskell} - match "posts/*" $ do - route $ setExtension ".html" - compile $ pageCompiler - >>> isPagePublished - >>> (id +++ (applyTemplateCompiler "templates/post.html" - >>> applyTemplateCompiler "templates/default.html" - >>> relativizeUrlsCompiler)) -~~~~~ - -The other problem with this solution is more severe: hakyll will no -longer generate the index and posts pages due to a rare problem in -haskell land: a runtime type error. Hakyll tries to be smart and reuse -the parsed pages from the `match "posts/*"` when processing the -`requireAllA "posts/*"` calls by caching them. But the compilers there -still expect a list of pages instead of a list of eithers, so we have -to replace `filterPublised` with something that works on the -latter. Luckily (or, probably, by design), `Data.Either` provides just -the function we need, so the new filtering compiler is actually -shorter that the original, even though it has a more intimidating -type: - -~~~~~{.haskell} -filterPublishedE :: Compiler (Page a, [Either (Page b) (Page b)]) (Page a, [Page b]) -filterPublishedE = id *** arr rights -~~~~~ - -## Timed releases - -Exploiting the fact that compilers are arrows, we can do more mixing -and matching of compilers to further refine how hakyll deals with page -attributes like `published`. Maybe you want `cron` to update your blog -while you are on vacation, so you want posts to be considered -published if the `published` field is either `true` or a time in the -past. - -If you happen to live in the UK in winter or enjoy to do time zone -calculation in your head, your new function to test if a page is -published and the compiler derived from it might then look like this - -~~~~~{.haskell} -isPublishedYet :: Page a -> UTCTime -> Bool -isPublishedYet page time = - let published = getField "published" page in - published == "true" || after published - where - after published = - let publishAt = parseTime defaultTimeLocale "%Y-%m-%d %H:%M" published in - fromMaybe False (fmap (\embargo -> embargo < time) publishAt) - -isPagePublishedYet :: Compiler (Page a, UTCTime) (Either (Page a) (Page a)) -isPagePublishedYet = arr (\(p,t) -> if isPublishedYet p t then Right p else Left p) -~~~~~ - -This compiler has a pair of a page and a time as its input, and we can -use yet another function from `Control.Arrow` to construct a compiler -that generates the input for it, the function `&&&`. It takes two -compilers (arrows) with the same input type and constructs a compiler -from that type to a pair of the output types of the two compilers. -For the first argument we take the `pageCompiler` which we already -call at the beginning of the page compilation. The second argument -should be a compiler with the same input type as `pageCompiler` that -returns the current time. But the current time lives in the IO monad -and does not at all depend on the resource the current page is -generated from, so we have to cheat a little bit by calling -`unsafeCompiler` with a function that ignores its argument and returns -an `IO UTCTime`, which `unsafeCompiler` will unwrap for us: - -~~~~~{.haskell} - match "posts/*" $ do - route $ setExtension ".html" - compile $ (pageCompiler &&& (unsafeCompiler (\_ -> getCurrentTime))) - >>> isPagePublishedYet - >>> (id +++ ( ... as above ...)) -~~~~~ - -This is all we have to change if we don't generate unpublished pages -at all. If we just hide them from the lists, the call to `|||` -discards the information that a page is not (yet) published that was -encoded in the `Either`. In that case we could use the `setField` -function from `Hakyll.Web.Page.Metadata` to rewrite the `published` -field of the left and right pages in `isPagePublished(Yet)` to -canonical values that the original `isPublished` function called from -`filterPublished` understands: - -~~~~~{.haskell} -isPagePublishedYet = arr (\(p,t) -> if isPublishedYet p t then pub p else unpub p) - where - pub p = Right $ setField "published" "true" p - unpub p = Left $ setField "published" "false" p -~~~~~ - -The final version of this code can be found in the timedblog example, -together with the required `import` statements. diff --git a/web/tutorials/06-guide.markdown b/web/tutorials/06-guide.markdown deleted file mode 100644 index e8c5800..0000000 --- a/web/tutorials/06-guide.markdown +++ /dev/null @@ -1,129 +0,0 @@ ---- -title: A Guide to the Hakyll Module Zoo -author: Brent Yorgey ---- - -The hakyll package [contains a bewildering array](/reference/) of -modules, and it's hard to know where to look when you are just getting -started---especially since many of them are only used by hakyll -internally and not that useful to website authors. This guide -provides a quick reference to the contents of the most important and -useful modules. - -## Core modules - -These are the modules containing the fundamental tools and concepts -you need to get started building a site with hakyll. - -* [Hakyll.Core.Compiler](/reference/Hakyll-Core-Compiler.html) - - This is one of the modules you should look at first. It defines the - fundamental `Compiler` type and has a bunch of documentation explaining how to - use `Compiler`s and their `Arrow`-based interface. - - It also defines many primitive `Compiler`s as well as several - variants on `require`, which allow you to bring together multiple - resources to create a single output. - -* [Hakyll.Core.Routes](/reference/Hakyll-Core-Routes.html) - - Specify where compiled items should go in the output site. - -* [Hakyll.Core.Rules](/reference/Hakyll-Core-Rules.html) - - Specify which compilers and routes should be used on which - resources. - - Also has combinators for grouping (necessary if you want to use - the same resources for multiple purposes), creating outputs that - are not based on any resources, and even dynamically generating - compilers. - -* [Hakyll.Core.Identifier.Pattern](/reference/Hakyll-Core-Identifier-Pattern.html) - - Combinators for creating *patterns*, i.e. predicates that pick out - a set of resources: filesystem globs, arbitrary predicates, - explicit lists, regular expressions, and so on. - -* [Hakyll.Web.Page](/reference/Hakyll-Web-Page.html) - - A `Page`, consisting of some metadata and a body, is one of the - most fundamental structures used by hakyll. This module has some - documentation explaining how pages work, and defines a number of - compilers and utilities for working with them. - -* [Hakyll.Web.Page.Metadata](/reference/Hakyll-Web-Page-Metadata.html) - - Utilities for manipulating page metadata. - -* [Hakyll.Web.Template](/reference/Hakyll-Web-Template.html) - - Templates specify how to take the content of a `Page` and turn - it into HTML output. - -* [Hakyll.Main](/reference/Hakyll-Main.html) - - The main `hakyll` function that runs the whole show. There is - also a `hakyllWith` function which allows for a custom - configuration. - -## Pre-packaged solutions - -These modules contain some "pre-packaged" solutions for common -situations. They can be used as-is, or their source can be used as -inspiration for your own tools. - -* [Hakyll.Web.Page.List](/reference/Hakyll-Web-Page-List.html) - - Combine several pages into a list, such as a list of posts, images - in a gallery, etc. - -* [Hakyll.Web.Feed](/reference/Hakyll-Web-Feed.html) - - Create RSS feeds. - -* [Hakyll.Web.Tags](/reference/Hakyll-Web-Tags.html) - - Work with tags and categories. - -## Useful utilities - -* [Hakyll.Core.UnixFilter](/reference/Hakyll-Core-UnixFilter.html) - - Use any unix utility as a compiler. - -* [Hakyll.Core.Util.Arrow](/reference/Hakyll-Core-Util-Arrow.html) - - A few utilities for working with arrows, including a constant - arrow, unit arrow, and running an entire list of arrows on a - single input. - -* [Hakyll.Core.Util.File](/reference/Hakyll-Core-Util-File.html) - - Utility functions for working with the file system. - -* [Hakyll.Core.Util.String](/reference/Hakyll-Core-Util-String.html) - - A few utility functions for working with `String`s (trim spaces, - find and replace, split on regexp). - -* [Hakyll.Core.Writable.WritableTuple](/reference/Hakyll-Core-Writable-WritableTuple.html) - - A utility type covering the situation where you generate some - data, some of which you want to write to disk, and some of which - you don't want to write but will be needed in order to generate - something else later. - -## Advanced customization - -* [Hakyll.Core.Writable](/reference/Hakyll-Core-Writable.html) - - The `Writable` class is for resources which can be written to disk - as part of the output site. You can specify how to write your own - custom types to disk by giving them a `Writable` instance. - -* [Hakyll.Web.Pandoc](/reference/Hakyll-Web-Pandoc.html) - - Some compilers for running pandoc. Normally they are run - automatically as part of, for example, `pageCompiler`; but - sometimes it is useful to be able to run pandoc explicitly. diff --git a/web/tutorials/guide.markdown b/web/tutorials/guide.markdown new file mode 100644 index 0000000..8376952 --- /dev/null +++ b/web/tutorials/guide.markdown @@ -0,0 +1,99 @@ +--- +title: A Guide to the Hakyll Module Zoo +author: Brent Yorgey +--- + +The hakyll package [contains a bewildering array](/reference/) of modules, and +it's hard to know where to look when you are just getting started -- especially +since many of them are mostly just used by Hakyll internally and not that useful +to website authors. This guide provides a quick reference to the contents of the +most important and useful modules. + +## Core modules + +These are the modules containing the fundamental tools and concepts +you need to get started building a site with hakyll. + +* [Hakyll.Core.Compiler](/reference/Hakyll-Core-Compiler.html) + + This is one of the modules you should look at first. It defines the + fundamental `Compiler` type and primitive `Compiler`s as well as several + variants on `load`, which allow you to bring together multiple resources to + create a single output. + +* [Hakyll.Core.Routes](/reference/Hakyll-Core-Routes.html) + + Specify where compiled items should go in the output site. + +* [Hakyll.Core.Rules](/reference/Hakyll-Core-Rules.html) + + Specify which compilers and routes should be used on which resources. Also + has combinators for versions (necessary if you want to use the same + resources for multiple purposes). + +* [Hakyll.Core.Identifier.Pattern](/reference/Hakyll-Core-Identifier-Pattern.html) + + Combinators for creating *patterns*, i.e. predicates that pick out a set of + resources: filesystem globs, explicit lists, regular expressions, and so on. + +* [Hakyll.Web.Page](/reference/Hakyll-Web-Pandoc.html) + + Provides functions for rendering your pages using pandoc, with a varying + degree of high-levelness. + +* [Hakyll.Web.Template](/reference/Hakyll-Web-Template.html) + + Templates specify how to take the content of an item and turn it into HTML + output. + +* [Hakyll.Web.Template.Context](/reference/Hakyll-Web-Template-Context.html) + + You can't do much with a `Template` if you don't have a `Context`: this + module provides some predefined `Context`s and the tools to build your own. + +* [Hakyll.Main](/reference/Hakyll-Main.html) + + The main `hakyll` function that runs the whole show. There is also a + `hakyllWith` function which allows for a custom configuration. + +## Pre-packaged solutions + +These modules contain some "pre-packaged" solutions for common situations. They +can be used as-is, or their source can be used as inspiration for your own +tools. + +* [Hakyll.Web.Page.List](/reference/Hakyll-Web-Page-List.html) + + Combine several pages into a list, such as a list of posts, images in a + gallery, etc. + +* [Hakyll.Web.Feed](/reference/Hakyll-Web-Feed.html) + + Create RSS feeds. + +* [Hakyll.Web.Tags](/reference/Hakyll-Web-Tags.html) + + Work with tags and categories. + +## Useful utilities + +* [Hakyll.Core.UnixFilter](/reference/Hakyll-Core-UnixFilter.html) + + Use any unix utility as a compiler. + +* [Hakyll.Core.Util.File](/reference/Hakyll-Core-Util-File.html) + + Utility functions for working with the file system. + +* [Hakyll.Core.Util.String](/reference/Hakyll-Core-Util-String.html) + + A few utility functions for working with `String`s (trim spaces, find and + replace, split on regexp). + +## Advanced customization + +* [Hakyll.Core.Writable](/reference/Hakyll-Core-Writable.html) + + The `Writable` class is for resources which can be written to disk as part + of the output site. You can specify how to write your own custom types to + disk by giving them a `Writable` instance. |