Eliminate the dollar sign hack (#203)

* Suffix symbol defun symbols with @#$%^%0@

* Eliminate the dollar-sign hack

* ConsSym0 and ConsSym1 aren't actually things, update them

* Use the suffix @#@ instead

CHANGES.md

@@ -3,6 +3,22 @@ Changelog for singletons project
 
 next
 ----
+* The suffix for defunctionalized names of symbolic functions (e.g., `(+)`) has
+  changed. Before, the promoted type name would be suffixed with some number of
+  dollar signs (e.g., `(:+$)` and `(:+$$)`) to indicate defunctionalization
+  symbols. Now, the promoted type name is first suffixed with `@#@` and
+  _then_ followed by dollar signs (e.g., `(:+@#@$)` and `(:+@#@$$)`).
+  Adopting this conventional eliminates naming conflicts that could arise for
+  functions that consisted of solely `$` symbols.
+
+* The promoted/singled/defunctionalized symbols for `($)` have changed:
+
+  * `($)`  is now `(:$)`
+  * `(%$)` is now `(%:$)`
+  * `($$)` is now `($@#@$)`, and `($$$)` is now `($@#@$$)`
+
+  This makes the treatment of `($)` consistent with other symbolic functions.
+
 * Add promoted and singled versions of `Show`, including `deriving` support.
 
 * Permit derived `Ord` instances for empty datatypes.

README.md

@@ -374,7 +374,7 @@ generates. Here are some examples showing how this is done:
 
    singleton constructor: `:%+:`
 
-   symbols: `:+:$`, `:+:$$`, `:+:$$$`
+   symbols: `:+:@#@$`, `:+:@#@$$`, `:+:@#@$$$`
 
 
 5. original value: `pred`
@@ -392,7 +392,7 @@ generates. Here are some examples showing how this is done:
 
    singleton value: `%:+`
 
-   symbols: `:+$`, `:+$$`, `:+$$$`
+   symbols: `:+@#@$`, `:+@#@$$`, `:+@#@$$$`
 
 
 7. original class: `Num`
@@ -412,7 +412,8 @@ generates. Here are some examples showing how this is done:
 Special names
 -------------
 
-There are some special cases, listed below (with asterisks\* denoting special treatment):
+There are some special cases, listed below (with asterisks\* denoting special
+treatment):
 
 1. original datatype: `[]`
 
@@ -421,13 +422,13 @@ There are some special cases, listed below (with asterisks\* denoting special tr
    singleton type\*: `SList`
 
 
-2.  original constructor: `[]`
+2. original constructor: `[]`
 
-    promoted type: `'[]`
+   promoted type: `'[]`
 
-    singleton constructor\*: `SNil`
+   singleton constructor\*: `SNil`
 
-    symbols\*: `NilSym0`
+   symbols\*: `NilSym0`
 
 
 3. original constructor: `:`
@@ -436,7 +437,7 @@ There are some special cases, listed below (with asterisks\* denoting special tr
 
    singleton constructor\*: `SCons`
 
-   symbols\*: `ConsSym0`, `ConsSym1`
+   symbols: `:@#@$`, `:@#@$`
 
 
 4. original datatype: `(,)`

src/Data/Promotion/Prelude.hs

@@ -46,7 +46,7 @@ module Data.Promotion.Prelude (
   PShow(..), ShowS, SChar, show_, (:<>), Shows, ShowChar, ShowString, ShowParen,
 
   -- ** Miscellaneous functions
-  Id, Const, (:.), type ($), type ($!), Flip, AsTypeOf, Until, Seq,
+  Id, Const, (:.), (:$), (:$!), Flip, AsTypeOf, Until, Seq,
 
   -- * List operations
   Map, (:++), Filter,
@@ -75,7 +75,9 @@ module Data.Promotion.Prelude (
 
   -- * Defunctionalization symbols
   FalseSym0, TrueSym0,
-  NotSym0, NotSym1, (:&&$), (:&&$$), (:&&$$$), (:||$), (:||$$), (:||$$$),
+  NotSym0, NotSym1,
+  (:&&@#@$), (:&&@#@$$), (:&&@#@$$$),
+  (:||@#@$), (:||@#@$$), (:||@#@$$$),
   OtherwiseSym0,
 
   NothingSym0, JustSym0, JustSym1,
@@ -95,27 +97,27 @@ module Data.Promotion.Prelude (
   CurrySym0, CurrySym1, CurrySym2, CurrySym3,
   UncurrySym0, UncurrySym1, UncurrySym2,
 
-  (:^$), (:^$$),
+  (:^@#@$), (:^@#@$$),
 
   ShowsPrecSym0, ShowsPrecSym1, ShowsPrecSym2, ShowsPrecSym3,
   Show_Sym0, Show_Sym1,
   ShowListSym0, ShowListSym1, ShowListSym2,
-  (:<>$), (:<>$$), (:<>$$$),
+  (:<>@#@$), (:<>@#@$$), (:<>@#@$$$),
   ShowsSym0, ShowsSym1, ShowsSym2,
   ShowCharSym0, ShowCharSym1, ShowCharSym2,
   ShowStringSym0, ShowStringSym1, ShowStringSym2,
   ShowParenSym0, ShowParenSym1, ShowParenSym2,
 
   IdSym0, IdSym1, ConstSym0, ConstSym1, ConstSym2,
-  (:.$), (:.$$), (:.$$$),
-  type ($$), type ($$$), type ($$$$),
-  type ($!$), type ($!$$), type ($!$$$),
+  (:.@#@$), (:.@#@$$), (:.@#@$$$),
+  (:$@#@$),  (:$@#@$$),  (:$@#@$$$),
+  (:$!@#@$), (:$!@#@$$), (:$!@#@$$$),
   FlipSym0, FlipSym1, FlipSym2,
   AsTypeOfSym0, AsTypeOfSym1, AsTypeOfSym2, SeqSym0, SeqSym1, SeqSym2,
 
-  (:$), (:$$), (:$$$), NilSym0,
+  (:@#@$), (:@#@$$), (:@#@$$$), NilSym0,
   MapSym0, MapSym1, MapSym2, ReverseSym0, ReverseSym1,
-  (:++$$), (:++$), HeadSym0, HeadSym1, LastSym0, LastSym1,
+  (:++@#@$$), (:++@#@$), HeadSym0, HeadSym1, LastSym0, LastSym1,
   TailSym0, TailSym1, InitSym0, InitSym1, NullSym0, NullSym1,
 
   FoldlSym0, FoldlSym1, FoldlSym2, FoldlSym3,
@@ -159,7 +161,7 @@ module Data.Promotion.Prelude (
   BreakSym0, BreakSym1, BreakSym2,
   LookupSym0, LookupSym1, LookupSym2,
   FilterSym0, FilterSym1, FilterSym2,
-  (:!!$), (:!!$$), (:!!$$$),
+  (:!!@#@$), (:!!@#@$$), (:!!@#@$$$),
   ) where
 
 import Data.Promotion.Prelude.Base

src/Data/Promotion/Prelude/Base.hs

@@ -23,19 +23,19 @@
 
 module Data.Promotion.Prelude.Base (
   -- * Promoted functions from @GHC.Base@
-  Foldr, Map, (:++), Otherwise, Id, Const, (:.), type ($), type ($!),
+  Foldr, Map, (:++), Otherwise, Id, Const, (:.), (:$), (:$!),
   Flip, Until, AsTypeOf, Seq,
 
   -- * Defunctionalization symbols
   FoldrSym0, FoldrSym1, FoldrSym2, FoldrSym3,
   MapSym0, MapSym1, MapSym2,
-  (:++$), (:++$$), (:++$$$),
+  (:++@#@$), (:++@#@$$), (:++@#@$$$),
   OtherwiseSym0,
   IdSym0, IdSym1,
   ConstSym0, ConstSym1, ConstSym2,
-  (:.$), (:.$$), (:.$$$), (:.$$$$),
-  type ($$), type ($$$), type ($$$$),
-  type ($!$), type ($!$$), type ($!$$$),
+  (:.@#@$), (:.@#@$$), (:.@#@$$$), (:.@#@$$$$),
+  (:$@#@$),  (:$@#@$$),  (:$@#@$$$),
+  (:$!@#@$), (:$!@#@$$), (:$!@#@$$$),
   FlipSym0, FlipSym1, FlipSym2, FlipSym3,
   UntilSym0, UntilSym1, UntilSym2, UntilSym3,
   AsTypeOfSym0, AsTypeOfSym1, AsTypeOfSym2,

src/Data/Promotion/Prelude/Bool.hs

@@ -33,8 +33,8 @@ module Data.Promotion.Prelude.Bool (
   TrueSym0, FalseSym0,
 
   NotSym0, NotSym1,
-  (:&&$), (:&&$$), (:&&$$$),
-  (:||$), (:||$$), (:||$$$),
+  (:&&@#@$), (:&&@#@$$), (:&&@#@$$$),
+  (:||@#@$), (:||@#@$$), (:||@#@$$$),
   Bool_Sym0, Bool_Sym1, Bool_Sym2, Bool_Sym3,
   OtherwiseSym0
   ) where

src/Data/Promotion/Prelude/Eq.hs

@@ -13,7 +13,9 @@
 
 {-# LANGUAGE ExplicitNamespaces #-}
 module Data.Promotion.Prelude.Eq (
-  PEq(..), (:==$), (:==$$), (:==$$$), (:/=$), (:/=$$), (:/=$$$)
+  PEq(..),
+  (:==@#@$), (:==@#@$$), (:==@#@$$$),
+  (:/=@#@$), (:/=@#@$$), (:/=@#@$$$)
   ) where
 
 import Data.Singletons.Prelude.Eq

src/Data/Promotion/Prelude/Function.hs

@@ -21,17 +21,17 @@
 
 module Data.Promotion.Prelude.Function (
     -- * "Prelude" re-exports
-    Id, Const, (:.), Flip, type ($)
+    Id, Const, (:.), Flip, (:$)
     -- * Other combinators
   , (:&), On
 
     -- * Defunctionalization symbols
   , IdSym0, IdSym1
   , ConstSym0, ConstSym1, ConstSym2
-  , (:.$), (:.$$), (:.$$$), (:.$$$$)
+  , (:.@#@$), (:.@#@$$), (:.@#@$$$), (:.@#@$$$$)
   , FlipSym0, FlipSym1, FlipSym2, FlipSym3
-  , type ($$), type ($$$), type ($$$$)
-  , (:&$), (:&$$), (:&$$$)
+  , (:$@#@$), (:$@#@$$), (:$@#@$$$)
+  , (:&@#@$), (:&@#@$$), (:&@#@$$$)
   , OnSym0, OnSym1, OnSym2, OnSym3, OnSym4
   ) where
 

src/Data/Promotion/Prelude/List.hs

@@ -102,9 +102,10 @@ module Data.Promotion.Prelude.List (
 
   -- * Defunctionalization symbols
   NilSym0,
-  (:$), (:$$), (:$$$),
+  (:@#@$), (:@#@$$), (:@#@$$$),
 
-  (:++$$$), (:++$$), (:++$), HeadSym0, HeadSym1, LastSym0, LastSym1,
+  (:++@#@$$$), (:++@#@$$), (:++@#@$),
+  HeadSym0, HeadSym1, LastSym0, LastSym1,
   TailSym0, TailSym1, InitSym0, InitSym1, NullSym0, NullSym1,
 
   MapSym0, MapSym1, MapSym2, ReverseSym0, ReverseSym1,
@@ -157,7 +158,7 @@ module Data.Promotion.Prelude.List (
   Unzip7Sym0, Unzip7Sym1,
 
   DeleteSym0, DeleteSym1, DeleteSym2,
-  (:\\$), (:\\$$), (:\\$$$),
+  (:\\@#@$), (:\\@#@$$), (:\\@#@$$$),
   IntersectSym0, IntersectSym1, IntersectSym2,
 
   InsertSym0, InsertSym1, InsertSym2,
@@ -193,7 +194,7 @@ module Data.Promotion.Prelude.List (
   FilterSym0, FilterSym1, FilterSym2,
   PartitionSym0, PartitionSym1, PartitionSym2,
 
-  (:!!$), (:!!$$), (:!!$$$),
+  (:!!@#@$), (:!!@#@$$), (:!!@#@$$$),
 
   ElemIndexSym0, ElemIndexSym1, ElemIndexSym2,
   ElemIndicesSym0, ElemIndicesSym1, ElemIndicesSym2,

src/Data/Promotion/Prelude/List/NonEmpty.hs

@@ -69,7 +69,7 @@ module Data.Promotion.Prelude.List.NonEmpty (
   Xor,
 
   -- * Defunctionalization symbols
-  (:|$), (:|$$), (:|$$$),
+  (:|@#@$), (:|@#@$$), (:|@#@$$$),
   MapSym0, MapSym1, MapSym2,
   IntersperseSym0, IntersperseSym1, IntersperseSym2,
   ScanlSym0, ScanlSym1, ScanlSym2, ScanlSym3,
@@ -84,7 +84,7 @@ module Data.Promotion.Prelude.List.NonEmpty (
   TailSym0, TailSym1,
   LastSym0, LastSym1,
   InitSym0, InitSym1,
-  (:<|$), (:<|$$), (:<|$$$),
+  (:<|@#@$), (:<|@#@$$), (:<|@#@$$$),
   ConsSym0, ConsSym1, ConsSym2,
   UnconsSym0, UnconsSym1,
   UnfoldrSym0, UnfoldrSym1, UnfoldrSym2,
@@ -114,7 +114,7 @@ module Data.Promotion.Prelude.List.NonEmpty (
   IsPrefixOfSym0, IsPrefixOfSym1, IsPrefixOfSym2,
   NubSym0, NubSym1,
   NubBySym0, NubBySym1, NubBySym2,
-  (:!!$), (:!!$$), (:!!$$$),
+  (:!!@#@$), (:!!@#@$$), (:!!@#@$$$),
   ZipSym0, ZipSym1, ZipSym2,
   ZipWithSym0, ZipWithSym1, ZipWithSym2, ZipWithSym3,
   UnzipSym0, UnzipSym1,

src/Data/Promotion/Prelude/Num.hs

@@ -16,9 +16,9 @@ module Data.Promotion.Prelude.Num (
   PNum(..), Subtract,
 
   -- ** Defunctionalization symbols
-  (:+$), (:+$$), (:+$$$),
-  (:-$), (:-$$), (:-$$$),
-  (:*$), (:*$$), (:*$$$),
+  (:+@#@$), (:+@#@$$), (:+@#@$$$),
+  (:-@#@$), (:-@#@$$), (:-@#@$$$),
+  (:*@#@$), (:*@#@$$), (:*@#@$$$),
   NegateSym0, NegateSym1,
   AbsSym0, AbsSym1,
   SignumSym0, SignumSym1,

src/Data/Promotion/Prelude/Ord.hs

@@ -15,10 +15,10 @@ module Data.Promotion.Prelude.Ord (
   POrd(..),
   LTSym0, EQSym0, GTSym0,
   CompareSym0, CompareSym1, CompareSym2,
-  (:<$), (:<$$), (:<$$$),
-  (:<=$), (:<=$$), (:<=$$$),
-  (:>$), (:>$$), (:>$$$),
-  (:>=$), (:>=$$), (:>=$$$),
+  (:<@#@$),  (:<@#@$$),  (:<@#@$$$),
+  (:<=@#@$), (:<=@#@$$), (:<=@#@$$$),
+  (:>@#@$),  (:>@#@$$),  (:>@#@$$$),
+  (:>=@#@$), (:>=@#@$$), (:>=@#@$$$),
   MaxSym0, MaxSym1, MaxSym2,
   MinSym0, MinSym1, MinSym2
   ) where

src/Data/Promotion/Prelude/Show.hs

@@ -20,7 +20,7 @@ module Data.Promotion.Prelude.Show (
   ShowsPrecSym0, ShowsPrecSym1, ShowsPrecSym2, ShowsPrecSym3,
   Show_Sym0, Show_Sym1,
   ShowListSym0, ShowListSym1, ShowListSym2,
-  (:<>$), (:<>$$), (:<>$$$),
+  (:<>@#@$), (:<>@#@$$), (:<>@#@$$$),
   ShowsSym0, ShowsSym1, ShowsSym2,
   ShowListWithSym0, ShowListWithSym1, ShowListWithSym2, ShowListWithSym3,
   ShowCharSym0, ShowCharSym1, ShowCharSym2,

src/Data/Singletons/Names.hs

@@ -175,7 +175,8 @@ promoteTySym name sat
     = let capped = toUpcaseStr noPrefix name in
       if isHsLetter (head capped)
       then mkName (capped ++ "Sym" ++ (show sat))
-      else mkName (capped ++ (replicate (sat + 1) '$'))
+      else mkName (capped ++ "@#@" -- See Note [Defunctionalization symbol suffixes]
+                          ++ (replicate (sat + 1) '$'))
 
 promoteClassName :: Name -> Name
 promoteClassName = prefixUCName "P" "#"
@@ -249,3 +250,30 @@ foldApply = foldl apply
 -- make and equality predicate
 mkEqPred :: DType -> DType -> DPred
 mkEqPred ty1 ty2 = foldl DAppPr (DConPr equalityName) [ty1, ty2]
+
+{-
+Note [Defunctionalization symbol suffixes]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Before, we used to denote defunctionalization symbols by simply appending dollar
+signs at the end (e.g., (:+$) and (:+$$)). But this can lead to ambiguity when you
+have function names that consist of solely $ characters. For instance, if you
+tried to promote ($) and ($$) simultaneously, you'd get these promoted types:
+
+:$
+:$$
+
+And these defunctionalization symbols:
+
+:$$
+:$$$
+
+But now there's a name clash between the promoted type for ($) and the
+defunctionalization symbol for ($$)! The solution is to use a precede these
+defunctionalization dollar signs with another string (we choose @#@).
+So now the new defunctionalization symbols would be:
+
+:$@#@$
+:$@#@$$
+
+And there is no conflict.
+-}

src/Data/Singletons/Prelude.hs

@@ -59,7 +59,7 @@ module Data.Singletons.Prelude (
   Shows, sShows, ShowChar, sShowChar, ShowString, sShowString, ShowParen, sShowParen,
 
   -- ** Miscellaneous functions
-  Id, sId, Const, sConst, (:.), (%:.), type ($), (%$), type ($!), (%$!),
+  Id, sId, Const, sConst, (:.), (%:.), (:$), (%:$), (:$!), (%:$!),
   Flip, sFlip, AsTypeOf, sAsTypeOf,
   Seq, sSeq,
 
@@ -94,7 +94,9 @@ module Data.Singletons.Prelude (
 
   -- * Defunctionalization symbols
   FalseSym0, TrueSym0,
-  NotSym0, NotSym1, (:&&$), (:&&$$), (:&&$$$), (:||$), (:||$$), (:||$$$),
+  NotSym0, NotSym1,
+  (:&&@#@$), (:&&@#@$$), (:&&@#@$$$),
+  (:||@#@$), (:||@#@$$), (:||@#@$$$),
   OtherwiseSym0,
 
   NothingSym0, JustSym0, JustSym1,
@@ -117,22 +119,22 @@ module Data.Singletons.Prelude (
   ShowsPrecSym0, ShowsPrecSym1, ShowsPrecSym2, ShowsPrecSym3,
   Show_Sym0, Show_Sym1,
   ShowListSym0, ShowListSym1, ShowListSym2,
-  (:<>$), (:<>$$), (:<>$$$),
+  (:<>@#@$), (:<>@#@$$), (:<>@#@$$$),
   ShowsSym0, ShowsSym1, ShowsSym2,
   ShowCharSym0, ShowCharSym1, ShowCharSym2,
   ShowStringSym0, ShowStringSym1, ShowStringSym2,
   ShowParenSym0, ShowParenSym1, ShowParenSym2,
 
   IdSym0, IdSym1, ConstSym0, ConstSym1, ConstSym2,
-  (:.$), (:.$$), (:.$$$),
-  type ($$), type ($$$), type ($$$$),
-  type ($!$), type ($!$$), type ($!$$$),
+  (:.@#@$), (:.@#@$$), (:.@#@$$$),
+  (:$@#@$),  (:$@#@$$),  (:$@#@$$$),
+  (:$!@#@$), (:$!@#@$$), (:$!@#@$$$),
   FlipSym0, FlipSym1, FlipSym2,
   AsTypeOfSym0, AsTypeOfSym1, AsTypeOfSym2, SeqSym0, SeqSym1, SeqSym2,
 
-  (:$), (:$$), (:$$$), NilSym0,
+  (:@#@$), (:@#@$$), (:@#@$$$), NilSym0,
   MapSym0, MapSym1, MapSym2, ReverseSym0, ReverseSym1,
-  (:++$$), (:++$), HeadSym0, HeadSym1, LastSym0, LastSym1,
+  (:++@#@$$), (:++@#@$), HeadSym0, HeadSym1, LastSym0, LastSym1,
   TailSym0, TailSym1, InitSym0, InitSym1, NullSym0, NullSym1,
 
   FoldlSym0, FoldlSym1, FoldlSym2, FoldlSym3,