{-# LANGUAGE CPP #-} #include "version-compatibility-macros.h" -- | -- Module : Prettyprinter -- Copyright : Daan Leijen (c) 2000, http://www.cs.uu.nl/~daan -- Max Bolingbroke (c) 2008, http://blog.omega-prime.co.uk -- David Luposchainsky (c) 2016, http://github.com/quchen -- License : BSD-style (see the file LICENSE.md) -- Maintainer : David Luposchainsky <dluposchainsky (λ) google> -- Stability : experimental -- Portability : portable -- -- = Overview -- -- This module defines a prettyprinter to format text in a flexible and -- convenient way. The idea is to combine a 'Doc'ument out of many small -- components, then using a layouter to convert it to an easily renderable -- 'SimpleDocStream', which can then be rendered to a variety of formats, for -- example plain 'Text'. -- -- The documentation consists of several parts: -- -- 1. Just below is some general information about the library. -- 2. The actual library with extensive documentation and examples -- 3. Migration guide for users familiar with (ansi-)wl-pprint -- -- == Starting out -- -- As a reading list for starters, some of the most commonly used functions in -- this module include '<>', 'hsep', '<+>', 'vsep', 'align', 'hang'. These cover -- many use cases already, and many other functions are variations or -- combinations of these. -- -- = Simple example -- -- Let’s prettyprint a simple Haskell type definition. First, intersperse @->@ -- and add a leading @::@, -- -- >>> let prettyType = align . sep . zipWith (<+>) ("::" : repeat "->") -- -- The 'sep' function is one way of concatenating documents, there are multiple -- others, e.g. 'vsep', 'cat' and 'fillSep'. In our case, 'sep' space-separates -- all entries if there is space, and newlines if the remaining line is too -- short. -- -- Second, prepend the name to the type, -- -- >>> let prettyDecl n tys = pretty n <+> prettyType tys -- -- Now we can define a document that contains some type signature: -- -- >>> let doc = prettyDecl "example" ["Int", "Bool", "Char", "IO ()"] -- -- This document can now be printed, and it automatically adapts to available -- space. If the page is wide enough (80 characters in this case), the -- definitions are space-separated, -- -- >>> putDocW 80 doc -- example :: Int -> Bool -> Char -> IO () -- -- If we narrow the page width to only 20 characters, the /same document/ -- renders vertically aligned: -- -- >>> putDocW 20 doc -- example :: Int -- -> Bool -- -> Char -- -> IO () -- -- Speaking of alignment, had we not used 'align', the @->@ would be at the -- beginning of each line, and not beneath the @::@. -- -- The 'Prettyprinter.Util.putDocW' renderer used here is from -- "Prettyprinter.Util". -- -- = General workflow -- -- @ -- ╔══════════╗ -- ║ ║ ╭────────────────────╮ -- ║ ║ │ 'vsep', 'pretty', '<+>', │ -- ║ ║ │ 'nest', 'align', … │ -- ║ ║ ╰─────────┬──────────╯ -- ║ ║ │ -- ║ Create ║ │ -- ║ ║ │ -- ║ ║ ▽ -- ║ ║ ╭───────────────────╮ -- ║ ║ │ 'Doc' │ -- ╠══════════╣ │ (rich document) │ -- ║ ║ ╰─────────┬─────────╯ -- ║ ║ │ -- ║ ║ │ Layout algorithms -- ║ Layout ║ │ e.g. 'layoutPretty' -- ║ ║ ▽ -- ║ ║ ╭───────────────────╮ -- ║ ║ │ 'SimpleDocStream' │ -- ╠══════════╣ │ (simple document) │ -- ║ ║ ╰─────────┬─────────╯ -- ║ ║ │ -- ║ ║ ├─────────────────────────────╮ -- ║ ║ │ │ 'Prettyprinter.Render.Util.SimpleDocTree.treeForm' -- ║ ║ │ ▽ -- ║ ║ │ ╭───────────────╮ -- ║ ║ │ │ 'Prettyprinter.Render.Util.SimpleDocTree.SimpleDocTree' │ -- ║ Render ║ │ ╰───────┬───────╯ -- ║ ║ │ │ -- ║ ║ ╭───────────────────┼─────────────────╮ ╭────────┴────────╮ -- ║ ║ │ │ │ │ │ -- ║ ║ ▽ ▽ ▽ ▽ ▽ -- ║ ║ ╭───────────────╮ ╭───────────────╮ ╭───────────────╮ ╭───────────────╮ -- ║ ║ │ ANSI terminal │ │ Plain 'Text' │ │ other/custom │ │ HTML │ -- ║ ║ ╰───────────────╯ ╰───────────────╯ ╰───────────────╯ ╰───────────────╯ -- ║ ║ -- ╚══════════╝ -- @ -- -- = How the layout works -- -- There are two key concepts to laying a document out: the available width, and -- 'group'ing. -- -- == Available width -- -- The page has a certain maximum width, which the layouter tries to not exceed, -- by inserting line breaks where possible. The functions given in this module -- make it fairly straightforward to specify where, and under what -- circumstances, such a line break may be inserted by the layouter, for example -- via the 'sep' function. -- -- There is also the concept of /ribbon width/. The ribbon is the part of a line -- that is printed, i.e. the line length without the leading indentation. The -- layouters take a ribbon fraction argument, which specifies how much of a line -- should be filled before trying to break it up. A ribbon width of 0.5 in a -- document of width 80 will result in the layouter to try to not exceed @0.5*80 = -- 40@ (ignoring current indentation depth). -- -- == Grouping -- -- A document can be 'group'ed, which tells the layouter that it should attempt -- to collapse it to a single line. If the result does not fit within the -- constraints (given by page and ribbon widths), the document is rendered -- unaltered. This allows fallback definitions, so that we get nice results even -- when the original document would exceed the layout constraints. -- -- = Things the prettyprinter /cannot/ do -- -- Due to how the Wadler/Leijen algorithm is designed, a couple of things are -- unsupported right now, with a high possibility of having no sensible -- implementation without significantly changing the layout algorithm. In -- particular, this includes -- -- * Leading symbols instead of just spaces for indentation, as used by the -- Linux @tree@ tool for example -- * Multi-column layouts, in particular tables with multiple cells of equal -- width adjacent to each other -- -- = Some helpful tips -- -- == Which kind of annotation should I use? -- -- __Summary:__ Use semantic annotations for @'Doc'@, and after layouting map to -- backend-specific ones. -- -- For example, suppose you want to prettyprint some programming language code. -- If you want keywords to be red, you should annotate the @'Doc'@ with a type -- that has a 'Keyword' field (without any notion of color), and then after -- layouting convert the annotations to map @'Keyword'@ to e.g. @'Red'@ (using -- @'reAnnotateS'@). The alternative that I /do not/ recommend is directly -- annotating the @'Doc'@ with 'Red'. -- -- While both versions would superficially work equally well and would create -- identical output, the recommended way has two significant advantages: -- modularity and extensibility. -- -- /Modularity:/ To change the color of keywords later, you have to touch one -- point, namely the mapping in @'reAnnotateS'@, where @'Keyword'@ is mapped to -- 'Red'. If you have @'annotate Red …'@ everywher, you’ll have to do a full -- text replacement, producing a large diff and touching lots of places for a -- very small change. -- -- /Extensibility:/ Adding a different backend in the recommended version is -- simply adding another @'reAnnotateS'@ to convert the @'Doc'@ annotation to -- something else. On the other hand, if you have @'Red'@ as an annotation in -- the @'Doc'@ already and the other backend does not support anything red -- (think of plain text or a website where red doesn’t work well with the rest -- of the style), you’ll have to worry about what to map »redness« to, which has -- no canonical answer. Should it be omitted? What does »red« mean anyway – -- maybe keywords and variables are red, and you want to change only the color -- of variables? module Prettyprinter ( -- * Documents Doc, -- * Basic functionality Pretty(..), viaShow, unsafeViaShow, emptyDoc, nest, line, line', softline, softline', hardline, -- ** Primitives for alternative layouts group, flatAlt, -- * Alignment functions -- -- | The functions in this section cannot be described by Wadler's original -- functions. They align their output relative to the current output -- position - in contrast to @'nest'@ which always aligns to the current -- nesting level. This deprives these functions from being \'optimal\'. In -- practice however they prove to be very useful. The functions in this -- section should be used with care, since they are more expensive than the -- other functions. For example, @'align'@ shouldn't be used to pretty print -- all top-level declarations of a language, but using @'hang'@ for let -- expressions is fine. align, hang, indent, encloseSep, list, tupled, -- * Binary functions (<>), (<+>), -- * List functions -- | The 'sep' and 'cat' functions differ in one detail: when 'group'ed, the -- 'sep's replace newlines wich 'space's, while the 'cat's simply remove -- them. If you're not sure what you want, start with the 'sep's. concatWith, -- ** 'sep' family -- -- | When 'group'ed, these will replace newlines with spaces. hsep, vsep, fillSep, sep, -- ** 'cat' family -- -- | When 'group'ed, these will remove newlines. hcat, vcat, fillCat, cat, -- ** Others punctuate, -- * Reactive/conditional layouts -- -- | Lay documents out differently based on current position and the page -- layout. column, nesting, width, pageWidth, -- * Filler functions -- -- | Fill up available space fill, fillBreak, -- * General convenience -- -- | Useful helper functions. plural, enclose, surround, -- * Bracketing functions -- -- | Enclose documents in common ways. squotes, dquotes, parens, angles, brackets, braces, -- * Named characters -- -- | Convenience definitions for common characters lparen, rparen, langle, rangle, lbrace, rbrace, lbracket, rbracket, squote, dquote, semi, colon, comma, space, dot, slash, backslash, equals, pipe, -- ** Annotations annotate, unAnnotate, reAnnotate, alterAnnotations, unAnnotateS, reAnnotateS, alterAnnotationsS, -- * Optimization -- -- Render documents faster fuse, FusionDepth(..), -- * Layout -- -- | Laying a 'Doc'ument out produces a straightforward 'SimpleDocStream' -- based on parameters such as page width and ribbon size, by evaluating how -- a 'Doc' fits these constraints the best. There are various ways to render -- a 'SimpleDocStream'. For the common case of rendering a 'SimpleDocStream' -- as plain 'Text' take a look at "Prettyprinter.Render.Text". SimpleDocStream(..), PageWidth(..), LayoutOptions(..), defaultLayoutOptions, layoutPretty, layoutCompact, layoutSmart, removeTrailingWhitespace, -- * Migration guide -- -- $migration ) where #if !(SEMIGROUP_MONOID_SUPERCLASS) import Data.Semigroup #endif import Prettyprinter.Internal import Prettyprinter.Symbols.Ascii -- $setup -- -- (Definitions for the doctests) -- -- >>> :set -XOverloadedStrings -- >>> import Prettyprinter.Render.Text -- >>> import Prettyprinter.Util -- $migration -- -- There are 3 main ways to migrate: -- -- 1. Direct: just replace the previous package and fix the errors -- 2. Using a drop-in replacement mimicing the API of the former module, see -- the @prettyprinter-compat-<former package>@ packages -- 3. Using a converter from the old @Doc@ type to the new one, see the -- @prettyprinter-convert-<former package>@ packages -- -- If you're already familiar with (ansi-)wl-pprint, you'll recognize many -- functions in this module, and they work just the same way. However, a couple -- of definitions are missing: -- -- - @char@, @string@, @double@, … – these are all special cases of the -- overloaded @'pretty'@ function. -- - @\<$>@, @\<$$>@, @\</>@, @\<//>@ are special cases of -- @'vsep'@, @'vcat'@, @'fillSep'@, @'fillCat'@ with only two documents. -- - If you need 'String' output, use the backends in the -- "Prettyprinter.Render.String" module. -- - The /display/ functions are moved to the rendering submodules, for -- example conversion to plain 'Text' is in the -- "Prettyprinter.Render.Text" module. -- - The /render/ functions are called /layout/ functions. -- - @SimpleDoc@ was renamed to @'SimpleDocStream'@, in order to make it -- clearer in the presence of @SimpleDocTree@. -- - Instead of providing an own colorization function for each -- color\/intensity\/layer combination, they have been combined in 'color', -- 'colorDull', 'bgColor', and 'bgColorDull' functions, which can be found -- in the ANSI terminal specific @prettyprinter-ansi-terminal@ package.