Render Iosevka ligatures to Private Use Area glyphs, for Emacs

README.md

Load IosevkaConfigGen.hs in a REPL and run toToml or toElisp to generate either TOML definitions for the glyphs (to put in parameters.toml), or a list of prettify-symbol-mode definitions for Emacs.

An example of generated TOML glyph definitions and elisp code are provided.

Note that

• I have a feature set called XALL in my fork that basically enables every possible ligation.

• I've hacked a few extra ligatures into my local checkout (including <<, >>, a few attempts to make more ->>--ish things a la Fira Code and Pragmata Pro, and also ligatures for <<< and >>> with a bit of extra space between the arrows because things look ugly without).

• I'm generating far more glyphs than there are ligatures for. In particular, I've added definitions for lots of things like <~> which aren't yet in Iosevka. The cool thing is that the generated glyphs end up looking almost exactly the same as "plain text". That is, plain <| and prettify-symbols-mode-enabled Unicode <| look the same. Once Iosevka gets those ligatures, I can just recompile Iosevka without having to change anything. (Besides restarting Emacs, ha.)

• A ton of the generated glyphs (hello ==>>>--) are stupid, but meh. I suppose having Pragmata-like equals chains with little indents near the end of each = might make those useful in Some Future ASCII APL/Haskell ("Jaskell"?) :P

IosevkaConfigGen.hs

{-# LANGUAGE RecordWildCards, Arrows #-}

import Numeric
import Data.Char

import Control.Monad
import Data.Monoid ((<>))
import Data.List (nub, sort, reverse)

data RepeatBounds = RB
  { str :: String
  , min :: Int
  , max :: Int
  } deriving Show

repeatFromTo s (min,max) = map (\n -> concat $ replicate n s) [min .. max]

tripleOp left mid right = [left <> mid, left <> mid <> right, mid <> right]

extended xs = map concat $ mapM renderGroup xs
  where renderGroup RB{..} = repeatFromTo str (min,max)

reverseArrow = reverse . map rev
  where
    rev xs =
      case xs of
        '>' -> '<'
        '<' -> '>'
        x -> x

angleArrows = rights <> map reverseArrow rights
  where
    rights = nub $
      [rgLeftHyphen, rgLeftHyphen', rgLeftEquals, rgLeftEquals'] >>= extended
    rgLeftHyphen = [RB "-" 1 2, RB ">" 1 3, RB "-" 0 2]
    rgLeftHyphen' = [RB "-" 0 2, RB ">" 1 3, RB "-" 1 2]
    rgLeftEquals = [RB "=" 1 2, RB ">" 1 3, RB "=" 0 2]
    rgLeftEquals' = [RB "=" 0 2, RB ">" 1 3, RB "=" 1 2]
    rgLeftTilde = [RB "~" 1 2, RB ">" 1 3, RB "-" 0 2]
    rgLeftTilde' = [RB "~" 1 2, RB ">" 1 3, RB "-" 0 0]

doubleEnded left mid right min max = do
  body <- mid `repeatFromTo` (min,max)
  pure (left ++ body ++ right)

rightEnded right mid = doubleEnded "" mid right
leftEnded left mid = doubleEnded left mid ""

hyphenDouble = doubleEnded "<" "-" ">" 1 5
equalsDouble = doubleEnded "<" "=" ">" 1 5
asteriskDouble = doubleEnded "<" "*" ">" 2 5

htmlCommentStart = leftEnded "<!" "-" 2 3

colons = repeatFromTo ":" (2,4)
dots = repeatFromTo "." (2,4)

tripleOps =
  concatMap
    (\mid -> tripleOp "<" mid ">")
    ["$", ".", "*", "\\", "/", "\"", "'", "^", "&", "%", "@", "#", "+", "-", "!", "?", "|", ":"]

lensOps =
  concat
    [ prefix' ":" "+-="
    , postfix' ":" "+-="
    , prefix' "=" "^+-*/%"
    , postfix' "=" "^+-*/%"
    ]
  where
    prefix str = map (str ++)
    prefix' str = prefix str . lift
    postfix str = map (++ str)
    postfix' str = postfix str . lift
    lift = map (: [])

addReversed xs = nub $ xs <> map reverseArrow xs

monadics = addReversed [">=>", ">->",">-->",">==>"]
composition = addReversed [">>", ">>>"]

logic = ["/\\", "\\/"]

semigroups = ["<>"] <> tripleOp "<" "+" ">"

allSeqs =
    [ ("Double-ended hyphen arrows", hyphenDouble)
    , ("Double-ended equals arrows",equalsDouble)
    , ("Double-ended asterisk operators",asteriskDouble)
    , ("HTML comments",htmlCommentStart)
    , ("Three-char ops with discards",tripleOps)
    , ("Colons",colons)
    , ("Arrow-like operators",angleArrows)
    , ("Monadic operators", monadics)
    , ("Composition operators", composition)
    , ("Lens operators",lensOps)
    , ("Logical", logic)
    , ("Semigroup/monoid operators", semigroups)
    ]

toToml = foldM_ go puaStart allSeqs
  where
    go start (sectionHeader, ligs) = do
      putStrLn "# -----------------------------------------"
      putStrLn $ "# " <> sectionHeader
      putStrLn "# -----------------------------------------\n"
      forM_ (enumerate start ligs) $ \(ix, lig) -> do
        putStrLn "[[iosevka.compLig]]"
        putStrLn $ "unicode = " <> show ix <> " # " <> toHex' "0x" ix
        putStrLn "featureTag = 'XALL'"
        putStrLn $ "sequence = " <> show lig
        putStrLn ""
      return $ start + length ligs

toElisp = foldM_ go puaStart allSeqs
  where
    go start (sectionHeader, ligs) = do
      putStrLn $ "\n;; " <> sectionHeader <> " ----------------"
      forM_ (enumerate start ligs) $ \(ix, lig) ->
        putStrLn $ "(" <> show lig <> " . " <> toHex' "#X" ix <> ")"
      return $ start + length ligs

enumerate start = zip [start ..]
puaStart = 0xE100
toHex n = showHex n ""
toHex' prefix = (prefix <>) . toHex

parameters.toml

# -----------------------------------------
# Double-ended hyphen arrows
# -----------------------------------------

[[iosevka.compLig]]
unicode = 57600 # 0xe100
featureTag = 'XALL'
sequence = "<->"

[[iosevka.compLig]]
unicode = 57601 # 0xe101
featureTag = 'XALL'
sequence = "<-->"

[[iosevka.compLig]]
unicode = 57602 # 0xe102
featureTag = 'XALL'
sequence = "<--->"

[[iosevka.compLig]]
unicode = 57603 # 0xe103
featureTag = 'XALL'
sequence = "<---->"

[[iosevka.compLig]]
unicode = 57604 # 0xe104
featureTag = 'XALL'
sequence = "<----->"

# -----------------------------------------
# Double-ended equals arrows
# -----------------------------------------

[[iosevka.compLig]]
unicode = 57605 # 0xe105
featureTag = 'XALL'
sequence = "<=>"

[[iosevka.compLig]]
unicode = 57606 # 0xe106
featureTag = 'XALL'
sequence = "<==>"

[[iosevka.compLig]]
unicode = 57607 # 0xe107
featureTag = 'XALL'
sequence = "<===>"

[[iosevka.compLig]]
unicode = 57608 # 0xe108
featureTag = 'XALL'
sequence = "<====>"

[[iosevka.compLig]]
unicode = 57609 # 0xe109
featureTag = 'XALL'
sequence = "<=====>"

# -----------------------------------------
# Double-ended asterisk operators
# -----------------------------------------

[[iosevka.compLig]]
unicode = 57610 # 0xe10a
featureTag = 'XALL'
sequence = "<**>"

[[iosevka.compLig]]
unicode = 57611 # 0xe10b
featureTag = 'XALL'
sequence = "<***>"

[[iosevka.compLig]]
unicode = 57612 # 0xe10c
featureTag = 'XALL'
sequence = "<****>"

[[iosevka.compLig]]
unicode = 57613 # 0xe10d
featureTag = 'XALL'
sequence = "<*****>"

# -----------------------------------------
# HTML comments
# -----------------------------------------

[[iosevka.compLig]]
unicode = 57614 # 0xe10e
featureTag = 'XALL'
sequence = "<!--"

[[iosevka.compLig]]
unicode = 57615 # 0xe10f
featureTag = 'XALL'
sequence = "<!---"

# -----------------------------------------
# Three-char ops with discards
# -----------------------------------------

[[iosevka.compLig]]
unicode = 57616 # 0xe110
featureTag = 'XALL'
sequence = "<$"

[[iosevka.compLig]]
unicode = 57617 # 0xe111
featureTag = 'XALL'
sequence = "<$>"

[[iosevka.compLig]]
unicode = 57618 # 0xe112
featureTag = 'XALL'
sequence = "$>"

[[iosevka.compLig]]
unicode = 57619 # 0xe113
featureTag = 'XALL'
sequence = "<."

[[iosevka.compLig]]
unicode = 57620 # 0xe114
featureTag = 'XALL'
sequence = "<.>"

[[iosevka.compLig]]
unicode = 57621 # 0xe115
featureTag = 'XALL'
sequence = ".>"

[[iosevka.compLig]]
unicode = 57622 # 0xe116
featureTag = 'XALL'
sequence = "<*"

[[iosevka.compLig]]
unicode = 57623 # 0xe117
featureTag = 'XALL'
sequence = "<*>"

[[iosevka.compLig]]
unicode = 57624 # 0xe118
featureTag = 'XALL'
sequence = "*>"

[[iosevka.compLig]]
unicode = 57625 # 0xe119
featureTag = 'XALL'
sequence = "<\\"

[[iosevka.compLig]]
unicode = 57626 # 0xe11a
featureTag = 'XALL'
sequence = "<\\>"

[[iosevka.compLig]]
unicode = 57627 # 0xe11b
featureTag = 'XALL'
sequence = "\\>"

[[iosevka.compLig]]
unicode = 57628 # 0xe11c
featureTag = 'XALL'
sequence = "</"

[[iosevka.compLig]]
unicode = 57629 # 0xe11d
featureTag = 'XALL'
sequence = "</>"

[[iosevka.compLig]]
unicode = 57630 # 0xe11e
featureTag = 'XALL'
sequence = "/>"

[[iosevka.compLig]]
unicode = 57631 # 0xe11f
featureTag = 'XALL'
sequence = "<\""

[[iosevka.compLig]]
unicode = 57632 # 0xe120
featureTag = 'XALL'
sequence = "<\">"

[[iosevka.compLig]]
unicode = 57633 # 0xe121
featureTag = 'XALL'
sequence = "\">"

[[iosevka.compLig]]
unicode = 57634 # 0xe122
featureTag = 'XALL'
sequence = "<'"

[[iosevka.compLig]]
unicode = 57635 # 0xe123
featureTag = 'XALL'
sequence = "<'>"

[[iosevka.compLig]]
unicode = 57636 # 0xe124
featureTag = 'XALL'
sequence = "'>"

[[iosevka.compLig]]
unicode = 57637 # 0xe125
featureTag = 'XALL'
sequence = "<^"

[[iosevka.compLig]]
unicode = 57638 # 0xe126
featureTag = 'XALL'
sequence = "<^>"

[[iosevka.compLig]]
unicode = 57639 # 0xe127
featureTag = 'XALL'
sequence = "^>"

[[iosevka.compLig]]
unicode = 57640 # 0xe128
featureTag = 'XALL'
sequence = "<&"

[[iosevka.compLig]]
unicode = 57641 # 0xe129
featureTag = 'XALL'
sequence = "<&>"

[[iosevka.compLig]]
unicode = 57642 # 0xe12a
featureTag = 'XALL'
sequence = "&>"

[[iosevka.compLig]]
unicode = 57643 # 0xe12b
featureTag = 'XALL'
sequence = "<%"

[[iosevka.compLig]]
unicode = 57644 # 0xe12c
featureTag = 'XALL'
sequence = "<%>"

[[iosevka.compLig]]
unicode = 57645 # 0xe12d
featureTag = 'XALL'
sequence = "%>"

[[iosevka.compLig]]
unicode = 57646 # 0xe12e
featureTag = 'XALL'
sequence = "<@"

[[iosevka.compLig]]
unicode = 57647 # 0xe12f
featureTag = 'XALL'
sequence = "<@>"

[[iosevka.compLig]]
unicode = 57648 # 0xe130
featureTag = 'XALL'
sequence = "@>"

[[iosevka.compLig]]
unicode = 57649 # 0xe131
featureTag = 'XALL'
sequence = "<#"

[[iosevka.compLig]]
unicode = 57650 # 0xe132
featureTag = 'XALL'
sequence = "<#>"

[[iosevka.compLig]]
unicode = 57651 # 0xe133
featureTag = 'XALL'
sequence = "#>"

[[iosevka.compLig]]
unicode = 57652 # 0xe134
featureTag = 'XALL'
sequence = "<+"

[[iosevka.compLig]]
unicode = 57653 # 0xe135
featureTag = 'XALL'
sequence = "<+>"

[[iosevka.compLig]]
unicode = 57654 # 0xe136
featureTag = 'XALL'
sequence = "+>"

[[iosevka.compLig]]
unicode = 57655 # 0xe137
featureTag = 'XALL'
sequence = "<-"

[[iosevka.compLig]]
unicode = 57656 # 0xe138
featureTag = 'XALL'
sequence = "<->"

[[iosevka.compLig]]
unicode = 57657 # 0xe139
featureTag = 'XALL'
sequence = "->"

[[iosevka.compLig]]
unicode = 57658 # 0xe13a
featureTag = 'XALL'
sequence = "<!"

[[iosevka.compLig]]
unicode = 57659 # 0xe13b
featureTag = 'XALL'
sequence = "<!>"

[[iosevka.compLig]]
unicode = 57660 # 0xe13c
featureTag = 'XALL'
sequence = "!>"

[[iosevka.compLig]]
unicode = 57661 # 0xe13d
featureTag = 'XALL'
sequence = "<?"

[[iosevka.compLig]]
unicode = 57662 # 0xe13e
featureTag = 'XALL'
sequence = "<?>"

[[iosevka.compLig]]
unicode = 57663 # 0xe13f
featureTag = 'XALL'
sequence = "?>"

[[iosevka.compLig]]
unicode = 57664 # 0xe140
featureTag = 'XALL'
sequence = "<|"

[[iosevka.compLig]]
unicode = 57665 # 0xe141
featureTag = 'XALL'
sequence = "<|>"

[[iosevka.compLig]]
unicode = 57666 # 0xe142
featureTag = 'XALL'
sequence = "|>"

[[iosevka.compLig]]
unicode = 57667 # 0xe143
featureTag = 'XALL'
sequence = "<:"

[[iosevka.compLig]]
unicode = 57668 # 0xe144
featureTag = 'XALL'
sequence = "<:>"

[[iosevka.compLig]]
unicode = 57669 # 0xe145
featureTag = 'XALL'
sequence = ":>"

# -----------------------------------------
# Colons
# -----------------------------------------

[[iosevka.compLig]]
unicode = 57670 # 0xe146
featureTag = 'XALL'
sequence = "::"

[[iosevka.compLig]]
unicode = 57671 # 0xe147
featureTag = 'XALL'
sequence = ":::"

[[iosevka.compLig]]
unicode = 57672 # 0xe148
featureTag = 'XALL'
sequence = "::::"

# -----------------------------------------
# Arrow-like operators
# -----------------------------------------

[[iosevka.compLig]]
unicode = 57673 # 0xe149
featureTag = 'XALL'
sequence = "->"

[[iosevka.compLig]]
unicode = 57674 # 0xe14a
featureTag = 'XALL'
sequence = "->-"

[[iosevka.compLig]]
unicode = 57675 # 0xe14b
featureTag = 'XALL'
sequence = "->--"

[[iosevka.compLig]]
unicode = 57676 # 0xe14c
featureTag = 'XALL'
sequence = "->>"

[[iosevka.compLig]]
unicode = 57677 # 0xe14d
featureTag = 'XALL'
sequence = "->>-"

[[iosevka.compLig]]
unicode = 57678 # 0xe14e
featureTag = 'XALL'
sequence = "->>--"

[[iosevka.compLig]]
unicode = 57679 # 0xe14f
featureTag = 'XALL'
sequence = "->>>"

[[iosevka.compLig]]
unicode = 57680 # 0xe150
featureTag = 'XALL'
sequence = "->>>-"

[[iosevka.compLig]]
unicode = 57681 # 0xe151
featureTag = 'XALL'
sequence = "->>>--"

[[iosevka.compLig]]
unicode = 57682 # 0xe152
featureTag = 'XALL'
sequence = "-->"

[[iosevka.compLig]]
unicode = 57683 # 0xe153
featureTag = 'XALL'
sequence = "-->-"

[[iosevka.compLig]]
unicode = 57684 # 0xe154
featureTag = 'XALL'
sequence = "-->--"

[[iosevka.compLig]]
unicode = 57685 # 0xe155
featureTag = 'XALL'
sequence = "-->>"

[[iosevka.compLig]]
unicode = 57686 # 0xe156
featureTag = 'XALL'
sequence = "-->>-"

[[iosevka.compLig]]
unicode = 57687 # 0xe157
featureTag = 'XALL'
sequence = "-->>--"

[[iosevka.compLig]]
unicode = 57688 # 0xe158
featureTag = 'XALL'
sequence = "-->>>"

[[iosevka.compLig]]
unicode = 57689 # 0xe159
featureTag = 'XALL'
sequence = "-->>>-"

[[iosevka.compLig]]
unicode = 57690 # 0xe15a
featureTag = 'XALL'
sequence = "-->>>--"

[[iosevka.compLig]]
unicode = 57691 # 0xe15b
featureTag = 'XALL'
sequence = ">-"

[[iosevka.compLig]]
unicode = 57692 # 0xe15c
featureTag = 'XALL'
sequence = ">--"

[[iosevka.compLig]]
unicode = 57693 # 0xe15d
featureTag = 'XALL'
sequence = ">>-"

[[iosevka.compLig]]
unicode = 57694 # 0xe15e
featureTag = 'XALL'
sequence = ">>--"

[[iosevka.compLig]]
unicode = 57695 # 0xe15f
featureTag = 'XALL'
sequence = ">>>-"

[[iosevka.compLig]]
unicode = 57696 # 0xe160
featureTag = 'XALL'
sequence = ">>>--"

[[iosevka.compLig]]
unicode = 57697 # 0xe161
featureTag = 'XALL'
sequence = "=>"

[[iosevka.compLig]]
unicode = 57698 # 0xe162
featureTag = 'XALL'
sequence = "=>="

[[iosevka.compLig]]
unicode = 57699 # 0xe163
featureTag = 'XALL'
sequence = "=>=="

[[iosevka.compLig]]
unicode = 57700 # 0xe164
featureTag = 'XALL'
sequence = "=>>"

[[iosevka.compLig]]
unicode = 57701 # 0xe165
featureTag = 'XALL'
sequence = "=>>="

[[iosevka.compLig]]
unicode = 57702 # 0xe166
featureTag = 'XALL'
sequence = "=>>=="

[[iosevka.compLig]]
unicode = 57703 # 0xe167
featureTag = 'XALL'
sequence = "=>>>"

[[iosevka.compLig]]
unicode = 57704 # 0xe168
featureTag = 'XALL'
sequence = "=>>>="

[[iosevka.compLig]]
unicode = 57705 # 0xe169
featureTag = 'XALL'
sequence = "=>>>=="

[[iosevka.compLig]]
unicode = 57706 # 0xe16a
featureTag = 'XALL'
sequence = "==>"

[[iosevka.compLig]]
unicode = 57707 # 0xe16b
featureTag = 'XALL'
sequence = "==>="

[[iosevka.compLig]]
unicode = 57708 # 0xe16c
featureTag = 'XALL'
sequence = "==>=="

[[iosevka.compLig]]
unicode = 57709 # 0xe16d
featureTag = 'XALL'
sequence = "==>>"

[[iosevka.compLig]]
unicode = 57710 # 0xe16e
featureTag = 'XALL'
sequence = "==>>="

[[iosevka.compLig]]
unicode = 57711 # 0xe16f
featureTag = 'XALL'
sequence = "==>>=="

[[iosevka.compLig]]
unicode = 57712 # 0xe170
featureTag = 'XALL'
sequence = "==>>>"

[[iosevka.compLig]]
unicode = 57713 # 0xe171
featureTag = 'XALL'
sequence = "==>>>="

[[iosevka.compLig]]
unicode = 57714 # 0xe172
featureTag = 'XALL'
sequence = "==>>>=="

[[iosevka.compLig]]
unicode = 57715 # 0xe173
featureTag = 'XALL'
sequence = ">="

[[iosevka.compLig]]
unicode = 57716 # 0xe174
featureTag = 'XALL'
sequence = ">=="

[[iosevka.compLig]]
unicode = 57717 # 0xe175
featureTag = 'XALL'
sequence = ">>="

[[iosevka.compLig]]
unicode = 57718 # 0xe176
featureTag = 'XALL'
sequence = ">>=="

[[iosevka.compLig]]
unicode = 57719 # 0xe177
featureTag = 'XALL'
sequence = ">>>="

[[iosevka.compLig]]
unicode = 57720 # 0xe178
featureTag = 'XALL'
sequence = ">>>=="

[[iosevka.compLig]]
unicode = 57721 # 0xe179
featureTag = 'XALL'
sequence = "<-"

[[iosevka.compLig]]
unicode = 57722 # 0xe17a
featureTag = 'XALL'
sequence = "-<-"

[[iosevka.compLig]]
unicode = 57723 # 0xe17b
featureTag = 'XALL'
sequence = "--<-"

[[iosevka.compLig]]
unicode = 57724 # 0xe17c
featureTag = 'XALL'
sequence = "<<-"

[[iosevka.compLig]]
unicode = 57725 # 0xe17d
featureTag = 'XALL'
sequence = "-<<-"

[[iosevka.compLig]]
unicode = 57726 # 0xe17e
featureTag = 'XALL'
sequence = "--<<-"

[[iosevka.compLig]]
unicode = 57727 # 0xe17f
featureTag = 'XALL'
sequence = "<<<-"

[[iosevka.compLig]]
unicode = 57728 # 0xe180
featureTag = 'XALL'
sequence = "-<<<-"

[[iosevka.compLig]]
unicode = 57729 # 0xe181
featureTag = 'XALL'
sequence = "--<<<-"

[[iosevka.compLig]]
unicode = 57730 # 0xe182
featureTag = 'XALL'
sequence = "<--"

[[iosevka.compLig]]
unicode = 57731 # 0xe183
featureTag = 'XALL'
sequence = "-<--"

[[iosevka.compLig]]
unicode = 57732 # 0xe184
featureTag = 'XALL'
sequence = "--<--"

[[iosevka.compLig]]
unicode = 57733 # 0xe185
featureTag = 'XALL'
sequence = "<<--"

[[iosevka.compLig]]
unicode = 57734 # 0xe186
featureTag = 'XALL'
sequence = "-<<--"

[[iosevka.compLig]]
unicode = 57735 # 0xe187
featureTag = 'XALL'
sequence = "--<<--"

[[iosevka.compLig]]
unicode = 57736 # 0xe188
featureTag = 'XALL'
sequence = "<<<--"

[[iosevka.compLig]]
unicode = 57737 # 0xe189
featureTag = 'XALL'
sequence = "-<<<--"

[[iosevka.compLig]]
unicode = 57738 # 0xe18a
featureTag = 'XALL'
sequence = "--<<<--"

[[iosevka.compLig]]
unicode = 57739 # 0xe18b
featureTag = 'XALL'
sequence = "-<"

[[iosevka.compLig]]
unicode = 57740 # 0xe18c
featureTag = 'XALL'
sequence = "--<"

[[iosevka.compLig]]
unicode = 57741 # 0xe18d
featureTag = 'XALL'
sequence = "-<<"

[[iosevka.compLig]]
unicode = 57742 # 0xe18e
featureTag = 'XALL'
sequence = "--<<"

[[iosevka.compLig]]
unicode = 57743 # 0xe18f
featureTag = 'XALL'
sequence = "-<<<"

[[iosevka.compLig]]
unicode = 57744 # 0xe190
featureTag = 'XALL'
sequence = "--<<<"

[[iosevka.compLig]]
unicode = 57745 # 0xe191
featureTag = 'XALL'
sequence = "<="

[[iosevka.compLig]]
unicode = 57746 # 0xe192
featureTag = 'XALL'
sequence = "=<="

[[iosevka.compLig]]
unicode = 57747 # 0xe193
featureTag = 'XALL'
sequence = "==<="

[[iosevka.compLig]]
unicode = 57748 # 0xe194
featureTag = 'XALL'
sequence = "<<="

[[iosevka.compLig]]
unicode = 57749 # 0xe195
featureTag = 'XALL'
sequence = "=<<="

[[iosevka.compLig]]
unicode = 57750 # 0xe196
featureTag = 'XALL'
sequence = "==<<="

[[iosevka.compLig]]
unicode = 57751 # 0xe197
featureTag = 'XALL'
sequence = "<<<="

[[iosevka.compLig]]
unicode = 57752 # 0xe198
featureTag = 'XALL'
sequence = "=<<<="

[[iosevka.compLig]]
unicode = 57753 # 0xe199
featureTag = 'XALL'
sequence = "==<<<="

[[iosevka.compLig]]
unicode = 57754 # 0xe19a
featureTag = 'XALL'
sequence = "<=="

[[iosevka.compLig]]
unicode = 57755 # 0xe19b
featureTag = 'XALL'
sequence = "=<=="

[[iosevka.compLig]]
unicode = 57756 # 0xe19c
featureTag = 'XALL'
sequence = "==<=="

[[iosevka.compLig]]
unicode = 57757 # 0xe19d
featureTag = 'XALL'
sequence = "<<=="

[[iosevka.compLig]]
unicode = 57758 # 0xe19e
featureTag = 'XALL'
sequence = "=<<=="

[[iosevka.compLig]]
unicode = 57759 # 0xe19f
featureTag = 'XALL'
sequence = "==<<=="

[[iosevka.compLig]]
unicode = 57760 # 0xe1a0
featureTag = 'XALL'
sequence = "<<<=="

[[iosevka.compLig]]
unicode = 57761 # 0xe1a1
featureTag = 'XALL'
sequence = "=<<<=="

[[iosevka.compLig]]
unicode = 57762 # 0xe1a2
featureTag = 'XALL'
sequence = "==<<<=="

[[iosevka.compLig]]
unicode = 57763 # 0xe1a3
featureTag = 'XALL'
sequence = "=<"

[[iosevka.compLig]]
unicode = 57764 # 0xe1a4
featureTag = 'XALL'
sequence = "==<"

[[iosevka.compLig]]
unicode = 57765 # 0xe1a5
featureTag = 'XALL'
sequence = "=<<"

[[iosevka.compLig]]
unicode = 57766 # 0xe1a6
featureTag = 'XALL'
sequence = "==<<"

[[iosevka.compLig]]
unicode = 57767 # 0xe1a7
featureTag = 'XALL'
sequence = "=<<<"

[[iosevka.compLig]]
unicode = 57768 # 0xe1a8
featureTag = 'XALL'
sequence = "==<<<"

# -----------------------------------------
# Monadic operators
# -----------------------------------------

[[iosevka.compLig]]
unicode = 57769 # 0xe1a9
featureTag = 'XALL'
sequence = ">=>"

[[iosevka.compLig]]
unicode = 57770 # 0xe1aa
featureTag = 'XALL'
sequence = ">->"

[[iosevka.compLig]]
unicode = 57771 # 0xe1ab
featureTag = 'XALL'
sequence = ">-->"

[[iosevka.compLig]]
unicode = 57772 # 0xe1ac
featureTag = 'XALL'
sequence = ">==>"

[[iosevka.compLig]]
unicode = 57773 # 0xe1ad
featureTag = 'XALL'
sequence = "<=<"

[[iosevka.compLig]]
unicode = 57774 # 0xe1ae
featureTag = 'XALL'
sequence = "<-<"

[[iosevka.compLig]]
unicode = 57775 # 0xe1af
featureTag = 'XALL'
sequence = "<--<"

[[iosevka.compLig]]
unicode = 57776 # 0xe1b0
featureTag = 'XALL'
sequence = "<==<"

# -----------------------------------------
# Composition operators
# -----------------------------------------

[[iosevka.compLig]]
unicode = 57777 # 0xe1b1
featureTag = 'XALL'
sequence = ">>"

[[iosevka.compLig]]
unicode = 57778 # 0xe1b2
featureTag = 'XALL'
sequence = ">>>"

[[iosevka.compLig]]
unicode = 57779 # 0xe1b3
featureTag = 'XALL'
sequence = "<<"

[[iosevka.compLig]]
unicode = 57780 # 0xe1b4
featureTag = 'XALL'
sequence = "<<<"

# -----------------------------------------
# Lens operators
# -----------------------------------------

[[iosevka.compLig]]
unicode = 57781 # 0xe1b5
featureTag = 'XALL'
sequence = ":+"

[[iosevka.compLig]]
unicode = 57782 # 0xe1b6
featureTag = 'XALL'
sequence = ":-"

[[iosevka.compLig]]
unicode = 57783 # 0xe1b7
featureTag = 'XALL'
sequence = ":="

[[iosevka.compLig]]
unicode = 57784 # 0xe1b8
featureTag = 'XALL'
sequence = "+:"

[[iosevka.compLig]]
unicode = 57785 # 0xe1b9
featureTag = 'XALL'
sequence = "-:"

[[iosevka.compLig]]
unicode = 57786 # 0xe1ba
featureTag = 'XALL'
sequence = "=:"

[[iosevka.compLig]]
unicode = 57787 # 0xe1bb
featureTag = 'XALL'
sequence = "=^"

[[iosevka.compLig]]
unicode = 57788 # 0xe1bc
featureTag = 'XALL'
sequence = "=+"

[[iosevka.compLig]]
unicode = 57789 # 0xe1bd
featureTag = 'XALL'
sequence = "=-"

[[iosevka.compLig]]
unicode = 57790 # 0xe1be
featureTag = 'XALL'
sequence = "=*"

[[iosevka.compLig]]
unicode = 57791 # 0xe1bf
featureTag = 'XALL'
sequence = "=/"

[[iosevka.compLig]]
unicode = 57792 # 0xe1c0
featureTag = 'XALL'
sequence = "=%"

[[iosevka.compLig]]
unicode = 57793 # 0xe1c1
featureTag = 'XALL'
sequence = "^="

[[iosevka.compLig]]
unicode = 57794 # 0xe1c2
featureTag = 'XALL'
sequence = "+="

[[iosevka.compLig]]
unicode = 57795 # 0xe1c3
featureTag = 'XALL'
sequence = "-="

[[iosevka.compLig]]
unicode = 57796 # 0xe1c4
featureTag = 'XALL'
sequence = "*="

[[iosevka.compLig]]
unicode = 57797 # 0xe1c5
featureTag = 'XALL'
sequence = "/="

[[iosevka.compLig]]
unicode = 57798 # 0xe1c6
featureTag = 'XALL'
sequence = "%="

# -----------------------------------------
# Logical
# -----------------------------------------

[[iosevka.compLig]]
unicode = 57799 # 0xe1c7
featureTag = 'XALL'
sequence = "/\\"

[[iosevka.compLig]]
unicode = 57800 # 0xe1c8
featureTag = 'XALL'
sequence = "\\/"

# -----------------------------------------
# Semigroup/monoid operators
# -----------------------------------------

[[iosevka.compLig]]
unicode = 57801 # 0xe1c9
featureTag = 'XALL'
sequence = "<>"

[[iosevka.compLig]]
unicode = 57802 # 0xe1ca
featureTag = 'XALL'
sequence = "<+"

[[iosevka.compLig]]
unicode = 57803 # 0xe1cb
featureTag = 'XALL'
sequence = "<+>"

[[iosevka.compLig]]
unicode = 57804 # 0xe1cc
featureTag = 'XALL'
sequence = "+>"

[[iosevka.compLig]]
unicode = 57805 # 0xe1cc
featureTag = 'XALL'
sequence = ">~>"

[[iosevka.compLig]]
unicode = 57806 # 0xe1cc
featureTag = 'XALL'
sequence = "<~>"

setup-ligatures.el

;; I use Spacemacs, so I put this in user-config
;; Note that the script above only generates the long list of pairs.
;; The surrounding code is stolen from the PragmataPro scripts floating around on Gist.

  (setq prettify-symbols-unprettify-at-point 'right-edge)

  (defun setup-iosevka-ligatures ()
    (setq prettify-symbols-alist
          (append prettify-symbols-alist '(

;; Double-ended hyphen arrows ----------------
("<->" . #Xe100)
("<-->" . #Xe101)
("<--->" . #Xe102)
("<---->" . #Xe103)
("<----->" . #Xe104)

;; Double-ended equals arrows ----------------
("<=>" . #Xe105)
("<==>" . #Xe106)
("<===>" . #Xe107)
("<====>" . #Xe108)
("<=====>" . #Xe109)

;; Double-ended asterisk operators ----------------
("<**>" . #Xe10a)
("<***>" . #Xe10b)
("<****>" . #Xe10c)
("<*****>" . #Xe10d)

;; HTML comments ----------------
("<!--" . #Xe10e)
("<!---" . #Xe10f)

;; Three-char ops with discards ----------------
("<$" . #Xe110)
("<$>" . #Xe111)
("$>" . #Xe112)
("<." . #Xe113)
("<.>" . #Xe114)
(".>" . #Xe115)
("<*" . #Xe116)
("<*>" . #Xe117)
("*>" . #Xe118)
("<\\" . #Xe119)
("<\\>" . #Xe11a)
("\\>" . #Xe11b)
("</" . #Xe11c)
("</>" . #Xe11d)
("/>" . #Xe11e)
("<\"" . #Xe11f)
("<\">" . #Xe120)
("\">" . #Xe121)
("<'" . #Xe122)
("<'>" . #Xe123)
("'>" . #Xe124)
("<^" . #Xe125)
("<^>" . #Xe126)
("^>" . #Xe127)
("<&" . #Xe128)
("<&>" . #Xe129)
("&>" . #Xe12a)
("<%" . #Xe12b)
("<%>" . #Xe12c)
("%>" . #Xe12d)
("<@" . #Xe12e)
("<@>" . #Xe12f)
("@>" . #Xe130)
("<#" . #Xe131)
("<#>" . #Xe132)
("#>" . #Xe133)
("<+" . #Xe134)
("<+>" . #Xe135)
("+>" . #Xe136)
("<-" . #Xe137)
("<->" . #Xe138)
("->" . #Xe139)
("<!" . #Xe13a)
("<!>" . #Xe13b)
("!>" . #Xe13c)
("<?" . #Xe13d)
("<?>" . #Xe13e)
("?>" . #Xe13f)
("<|" . #Xe140)
("<|>" . #Xe141)
("|>" . #Xe142)
("<:" . #Xe143)
("<:>" . #Xe144)
(":>" . #Xe145)

;; Colons ----------------
("::" . #Xe146)
(":::" . #Xe147)
("::::" . #Xe148)

;; Arrow-like operators ----------------
("->" . #Xe149)
("->-" . #Xe14a)
("->--" . #Xe14b)
("->>" . #Xe14c)
("->>-" . #Xe14d)
("->>--" . #Xe14e)
("->>>" . #Xe14f)
("->>>-" . #Xe150)
("->>>--" . #Xe151)
("-->" . #Xe152)
("-->-" . #Xe153)
("-->--" . #Xe154)
("-->>" . #Xe155)
("-->>-" . #Xe156)
("-->>--" . #Xe157)
("-->>>" . #Xe158)
("-->>>-" . #Xe159)
("-->>>--" . #Xe15a)
(">-" . #Xe15b)
(">--" . #Xe15c)
(">>-" . #Xe15d)
(">>--" . #Xe15e)
(">>>-" . #Xe15f)
(">>>--" . #Xe160)
("=>" . #Xe161)
("=>=" . #Xe162)
("=>==" . #Xe163)
("=>>" . #Xe164)
("=>>=" . #Xe165)
("=>>==" . #Xe166)
("=>>>" . #Xe167)
("=>>>=" . #Xe168)
("=>>>==" . #Xe169)
("==>" . #Xe16a)
("==>=" . #Xe16b)
("==>==" . #Xe16c)
("==>>" . #Xe16d)
("==>>=" . #Xe16e)
("==>>==" . #Xe16f)
("==>>>" . #Xe170)
("==>>>=" . #Xe171)
("==>>>==" . #Xe172)
(">=" . #Xe173)
(">==" . #Xe174)
(">>=" . #Xe175)
(">>==" . #Xe176)
(">>>=" . #Xe177)
(">>>==" . #Xe178)
("<-" . #Xe179)
("-<-" . #Xe17a)
("--<-" . #Xe17b)
("<<-" . #Xe17c)
("-<<-" . #Xe17d)
("--<<-" . #Xe17e)
("<<<-" . #Xe17f)
("-<<<-" . #Xe180)
("--<<<-" . #Xe181)
("<--" . #Xe182)
("-<--" . #Xe183)
("--<--" . #Xe184)
("<<--" . #Xe185)
("-<<--" . #Xe186)
("--<<--" . #Xe187)
("<<<--" . #Xe188)
("-<<<--" . #Xe189)
("--<<<--" . #Xe18a)
("-<" . #Xe18b)
("--<" . #Xe18c)
("-<<" . #Xe18d)
("--<<" . #Xe18e)
("-<<<" . #Xe18f)
("--<<<" . #Xe190)
("<=" . #Xe191)
("=<=" . #Xe192)
("==<=" . #Xe193)
("<<=" . #Xe194)
("=<<=" . #Xe195)
("==<<=" . #Xe196)
("<<<=" . #Xe197)
("=<<<=" . #Xe198)
("==<<<=" . #Xe199)
("<==" . #Xe19a)
("=<==" . #Xe19b)
("==<==" . #Xe19c)
("<<==" . #Xe19d)
("=<<==" . #Xe19e)
("==<<==" . #Xe19f)
("<<<==" . #Xe1a0)
("=<<<==" . #Xe1a1)
("==<<<==" . #Xe1a2)
("=<" . #Xe1a3)
("==<" . #Xe1a4)
("=<<" . #Xe1a5)
("==<<" . #Xe1a6)
("=<<<" . #Xe1a7)
("==<<<" . #Xe1a8)

;; Monadic operators ----------------
(">=>" . #Xe1a9)
(">->" . #Xe1aa)
(">-->" . #Xe1ab)
(">==>" . #Xe1ac)
("<=<" . #Xe1ad)
("<-<" . #Xe1ae)
("<--<" . #Xe1af)
("<==<" . #Xe1b0)

;; Composition operators ----------------
(">>" . #Xe1b1)
(">>>" . #Xe1b2)
("<<" . #Xe1b3)
("<<<" . #Xe1b4)

;; Lens operators ----------------
(":+" . #Xe1b5)
(":-" . #Xe1b6)
(":=" . #Xe1b7)
("+:" . #Xe1b8)
("-:" . #Xe1b9)
("=:" . #Xe1ba)
("=^" . #Xe1bb)
("=+" . #Xe1bc)
("=-" . #Xe1bd)
("=*" . #Xe1be)
("=/" . #Xe1bf)
("=%" . #Xe1c0)
("^=" . #Xe1c1)
("+=" . #Xe1c2)
("-=" . #Xe1c3)
("*=" . #Xe1c4)
("/=" . #Xe1c5)
("%=" . #Xe1c6)

;; Logical ----------------
("/\\" . #Xe1c7)
("\\/" . #Xe1c8)

;; Semigroup/monoid operators ----------------
("<>" . #Xe1c9)
("<+" . #Xe1ca)
("<+>" . #Xe1cb)
("+>" . #Xe1cc)
             ))))

  (defun refresh-pretty ()
    (prettify-symbols-mode -1)
    (prettify-symbols-mode +1))

  ;; Hooks for modes in which to install the Iosevka ligatures
  (mapc (lambda (hook)
          (add-hook hook (lambda () (setup-iosevka-ligatures) (refresh-pretty))))
        '(text-mode-hook
          prog-mode-hook))
  (global-prettify-symbols-mode +1)

@peschkaj Try it again with the dev branch,

Also parameters.toml shouldn't be touched, rather add it now to private-build-plans.toml:

[[buildPlans.iosevka-custom.compatibility-ligatures]]
unicode = 57657 # 0xE139
featureTag = 'calt'
sequence = '->'

The problem was the glyphs weren't being added to the font during compilation. You can see if it was added: on linux with GNOME Unicode Charmap