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148 lines
6.8 KiB
148 lines
6.8 KiB
5 years ago
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## Vim Haskell Conceal+
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This bundle provides extended Haskell Conceal feature for Vim. The feature
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is used to display unicode operators in Haskell code without changing the
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underlying file.
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This package offers more (and, more importantly, configurable) features
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than the
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[baseline vim-haskellConcealbundle](https://github.com/Twinside/vim-haskellConceal).
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The baseline bundle has numerous forks, which is possible to combine, so
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everyone is welcome to share, improve or contribute new notations to this
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Conceal Plus package.
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GitHub: https://github.com/enomsg/vim-haskellConcealPlus
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### Why Concealing
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- Using things like '->' instead real arrows '→' was never a deliberate
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choice, but a choice made due to limitations of teletypewriters and
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input inconvenience.
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- With concealing you don't have to deal with cumbersome unicode-input
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methods, yet you can enjoy proper notation.
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- It is not only about aesthetics. Excess of multi-character functions may
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create visual noise, which negatively affects readability. Using special
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symbols and true arrows, together with colors and bold/italic face seems
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to improve the situation. The image shows Vim with and without
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concealing, both running in a plain terminal emulator:
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- Using concealing instead of *-unicode* versions of packages also has
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some advantages. Mainly, concealing does not require any changes to the
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source code, it is backwards-compatible with idiomatic code. Secondly,
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with concealing no special input methods are needed. Plus, currently
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some features are hardly possible without editor's concealing (e.g.
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power superscripts).
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### Installation
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Using Vim built-in `pack` support:
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```
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$ mkdir -p ~/.vim/pack/vim-haskellConcealPlus/start
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$ cd ~/.vim/pack/vim-haskellConcealPlus/start
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$ git clone https://github.com/enomsg/vim-haskellConcealPlus
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$ echo "syn on" >> ~/.vimrc # If not already in .vimrc
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$ echo "setlocal conceallevel=2" >> ~/.vimrc # If not already in .vimrc
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$ echo "set concealcursor=nciv" >> ~/.vimrc # Optional
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```
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### Available Options
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'q' option to disable concealing of scientific constants (e.g. π)
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'℘' option to disable concealing of powerset function
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'𝐒' option to disable String type to 𝐒 concealing
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'𝐓' option to disable Text type to 𝐓 concealing
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'𝐄' option to disable Either/Right/Left to 𝐄/𝑅/𝐿 concealing
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'𝐌' option to disable Maybe/Just/Nothing to 𝐌/𝐽/𝑁 concealing
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'A' option to not try to preserve indentation
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's' option to disable space consumption after ∑,∏,√ and ¬ functions
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'*' option to enable concealing of asterisk with '⋅' sign
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'x' option to disable default concealing of asterisk with '×' sign
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'E' option to enable ellipsis concealing with ‥ (two dot leader)
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'e' option to disable ellipsis concealing with … (ellipsis sign)
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'⇒' option to disable `implies` concealing with ⇒
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'⇔' option to disable `iff` concealing with ⇔
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'r' option to disable return (η) and join (µ) concealing
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'b' option to disable bind (left and right) concealing
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'f' option to enable formal (★) right bind concealing
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'c' option to enable encircled b/d (ⓑ/ⓓ) for right and left binds
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'h' option to enable partial concealing of binds (e.g. »=)
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'C' option to enable encircled 'm' letter ⓜ concealing for fmap
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'l' option to disable fmap/lift concealing with ↥
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'↱' option to disable mapM/forM concealing with ↱/↰
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'w' option to disable 'where' concealing with "due to"/∵ symbol
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'-' option to disable subtract/(-) concealing with ⊟
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'I' option to enable alternative ':+' concealing with with ⨢
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'i' option to disable default concealing of ':+' with ⅈ
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'R' option to disable realPart/imagPart concealing with ℜ/ℑ
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'T' option to enable True/False constants concealing with bold 𝐓/𝐅
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't' option to disable True/False constants concealing with italic 𝑇/𝐹
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'B' option to disable Bool type to 𝔹 concealing
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'Q' option to disable Rational type to ℚ concealing
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'Z' option to disable Integer type to ℤ concealing
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'N' option to disable Natural, Nat types to ℕ concealing
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'D' option to disable Double type to 𝔻 concealing
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'C' option to disable Complex type to ℂ concealing
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'1' option to disable numeric superscripts concealing, e.g. x²
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'a' option to disable alphabet superscripts concealing, e.g. xⁿ
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The flags can be specified via hscoptions variable. For example, *let
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hscoptions="fc"* in your *~/.vimrc*.
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### Known Issues and Hints:
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- Concealing may seriously mess up indentation. By default the bundle
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tries to preserve spaces for commonly troublesome symbols (e.g. ->, <-
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and => arrows). But to be sure about indentation, you still have to see
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the non-concealed code. *set conceallevel=0* might be handy in these
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cases.
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- *set concealcursor=nciv* seem to not play well with Vim matchparen
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feature (which is enabled by default). You can either disable concealing
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under the cursor, or disable matchparen by adding *let
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loaded_matchparen=1* at the very top of your *~/.vimrc*.
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- With *set concealcursor=nciv* navigation through concealed parts of code
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might be somewhat irritating because the cursor behaves a bit
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differently. It becomes less of an issue if you are used to Vim's *w/b*
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commands (word forward/backward). You can also try *set
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concealcursor=ncv* instead.
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- Finding proper fonts might be a pain. Most of modern, so called
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programming fonts (*Inconsolata*, *Anonymous Pro*, etc.) often lack
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decent unicode support. As a recommendation, try *DejaVu Sans Mono*.
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**Update**: thanks to [monospacifier](https://github.com/cpitclaudel/monospacifier)
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package, fonts are no longer a problem. Pick your favourite font, then in
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addition download one of the "monospacified" fallback fonts, save into
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`~/.fonts`, and adjust fontconfig, e.g.
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`~/.config/fontconfig/fonts.conf`:
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```
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<?xml version="1.0"?><!DOCTYPE fontconfig SYSTEM "fonts.dtd">
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<fontconfig>
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<dir>~/.fonts</dir>
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<alias>
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<family>monospace</family>
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<prefer>
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<family>TeX Gyre Schola Math monospacified for DejaVu Sans Mono</family>
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</prefer>
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</alias>
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</fontconfig>
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```
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- Most of the terminal emulators have one or more issues with regard to the
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unicode characters handling. Emulators that don't have problems with unicode
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might be pretty slow. As a recommendation, try xst, or *evilvte* (it has weird
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configuration, but draws things correctly) or *lxterminal* (seems to be quite
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capable, but limited configurability) or any other terminal emulator that
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happened to work for you.
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[xst](https://github.com/gnotclub/xst) is known to work well with DejaVu Sans
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Mono, plus [monospacified](https://github.com/cpitclaudel/monospacifier) fonts
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as a fallback.
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