Support for empty sets and maps. Alternate syntax for maps and lists:

sets, maps and lists are now homogeneous.

Lists by extension now require the "list" keyword, like sets and
maps. Semicolons needed, instead of commas.

New syntax for lists: `list [e_1; e_2; ...; e_n]`.

The empty list can now be denoted either by `list []` or `list end` or
`nil'.

Both `list` and `nil` are new keywords. Lists can also be denoted
without brackets, as sets and maps: `list e_1; e_2; ...; e_n end`.

The extension for maps follows the extension for sets: `map [b_1; b_2;
...; b_n]` or `maps b_1; ...; b_n end`.

AST.ml

@@ -39,6 +39,7 @@ let sepseq_to_region to_region = function
 
 (* Keywords of LIGO *)
 
+type keyword        = Region.t
 type kwd_and        = Region.t
 type kwd_begin      = Region.t
 type kwd_block      = Region.t
@@ -56,8 +57,10 @@ type kwd_function   = Region.t
 type kwd_if         = Region.t
 type kwd_in         = Region.t
 type kwd_is         = Region.t
+type kwd_list       = Region.t
 type kwd_map        = Region.t
 type kwd_mod        = Region.t
+type kwd_nil        = Region.t
 type kwd_not        = Region.t
 type kwd_of         = Region.t
 type kwd_or         = Region.t
@@ -378,10 +381,10 @@ and map_patch  = {
 }
 
 and map_injection = {
-  opening    : kwd_map;
+  opening    : opening;
-  bindings   : (binding reg, semi) nsepseq;
+  bindings   : (binding reg, semi) sepseq;
   terminator : semi option;
-  closing    : kwd_end
+  closing    : closing
 }
 
 and binding = {
@@ -518,12 +521,20 @@ and set_expr =
   SetInj of set_injection reg
 
 and set_injection = {
-  opening    : kwd_set;
+  opening    : opening;
-  elements   : (expr, semi) nsepseq;
+  elements   : (expr, semi) sepseq;
   terminator : semi option;
-  closing    : kwd_end
+  closing    : closing
 }
 
+and opening =
+  Kwd        of keyword
+| KwdBracket of keyword * lbracket
+
+and closing =
+  End       of kwd_end
+| RBracket  of rbracket
+
 and map_expr =
   MapLookUp of map_lookup reg
 | MapInj    of map_injection reg
@@ -582,8 +593,21 @@ and string_expr =
 
 and list_expr =
   Cons of cons bin_op reg
-| List      of (expr, comma) nsepseq brackets reg
+| List of list_injection reg
-| EmptyList of empty_list reg
+| Nil  of nil par reg
+
+and list_injection = {
+  opening    : opening;
+  elements   : (expr, semi) sepseq;
+  terminator : semi option;
+  closing    : closing
+}
+
+and nil = {
+  nil       : kwd_nil;
+  colon     : colon;
+  list_type : type_expr
+}
 
 and constr_expr =
   SomeApp   of (c_Some * arguments) reg
@@ -615,15 +639,6 @@ and record_projection = {
 
 and tuple = (expr, comma) nsepseq par reg
 
-and empty_list = typed_empty_list par
-
-and typed_empty_list = {
-  lbracket  : lbracket;
-  rbracket  : rbracket;
-  colon     : colon;
-  list_type : type_expr
-}
-
 and none_expr = typed_none_expr par
 
 and typed_none_expr = {
@@ -727,7 +742,7 @@ and string_expr_to_region = function
 and list_expr_to_region = function
   Cons {region; _}
 | List {region; _}
-| EmptyList {region; _} -> region
+| Nil  {region; _} -> region
 
 and constr_expr_to_region = function
   NoneExpr  {region; _}
@@ -1283,8 +1298,8 @@ and print_string_expr = function
 and print_list_expr = function
   Cons {value = {arg1; op; arg2}; _} ->
     print_expr arg1; print_token op "#"; print_expr arg2
-| List e       -> print_list e
+| List e -> print_list_injection e
-| EmptyList e  -> print_empty_list e
+| Nil  e -> print_nil e
 
 and print_constr_expr = function
   SomeApp e   -> print_some_app e
@@ -1356,17 +1371,27 @@ and print_set_remove node =
 
 and print_map_injection {value; _} =
   let {opening; bindings; terminator; closing} = value in
-  print_token opening "map";
+  print_opening "map" opening;
-  print_nsepseq ";" print_binding bindings;
+  print_sepseq ";" print_binding bindings;
   print_terminator terminator;
-  print_token closing "end"
+  print_closing closing
 
 and print_set_injection {value; _} =
-  let {opening; elements; terminator; closing} = value in
+  let {opening; elements; terminator; closing} : set_injection = value in
-  print_token opening "set";
+  print_opening "set" opening;
-  print_nsepseq ";" print_expr elements;
+  print_sepseq ";" print_expr elements;
   print_terminator terminator;
-  print_token closing "end"
+  print_closing closing
+
+and print_opening lexeme = function
+  Kwd kwd -> print_token kwd lexeme
+| KwdBracket (kwd, lbracket) ->
+    print_token kwd lexeme;
+    print_token lbracket "{"
+
+and print_closing = function
+  RBracket rbracket -> print_token rbracket "}"
+| End kwd_end       -> print_token kwd_end "end"
 
 and print_binding {value; _} =
   let {source; arrow; image} = value in
@@ -1380,18 +1405,18 @@ and print_tuple {value; _} =
   print_nsepseq "," print_expr inside;
   print_token rpar ")"
 
-and print_list {value; _} =
+and print_list_injection {value; _} =
-  let {lbracket; inside; rbracket} = value in
+  let {opening; elements; terminator; closing} : list_injection = value in
-  print_token lbracket "[";
+  print_opening "list" opening;
-  print_nsepseq "," print_expr inside;
+  print_sepseq ";" print_expr elements;
-  print_token rbracket "]"
+  print_terminator terminator;
+  print_closing closing
 
-and print_empty_list {value; _} =
+and print_nil {value; _} =
   let {lpar; inside; rpar} = value in
-  let {lbracket; rbracket; colon; list_type} = inside in
+  let {nil; colon; list_type} = inside in
   print_token     lpar "(";
-  print_token     lbracket "[";
+  print_token     nil "nil";
-  print_token     rbracket "]";
   print_token     colon ":";
   print_type_expr list_type;
   print_token     rpar ")"

AST.mli

@@ -23,6 +23,7 @@ val sepseq_to_region  : ('a -> Region.t) -> ('a,'sep) sepseq -> Region.t
 
 (* Keywords of LIGO *)
 
+type keyword        = Region.t
 type kwd_and        = Region.t
 type kwd_begin      = Region.t
 type kwd_block      = Region.t
@@ -40,8 +41,10 @@ type kwd_function   = Region.t
 type kwd_if         = Region.t
 type kwd_in         = Region.t
 type kwd_is         = Region.t
+type kwd_list       = Region.t
 type kwd_map        = Region.t
 type kwd_mod        = Region.t
+type kwd_nil        = Region.t
 type kwd_not        = Region.t
 type kwd_of         = Region.t
 type kwd_or         = Region.t
@@ -362,10 +365,10 @@ and map_patch  = {
 }
 
 and map_injection = {
-  opening    : kwd_map;
+  opening    : opening;
-  bindings   : (binding reg, semi) nsepseq;
+  bindings   : (binding reg, semi) sepseq;
   terminator : semi option;
-  closing    : kwd_end
+  closing    : closing
 }
 
 and binding = {
@@ -502,12 +505,20 @@ and set_expr =
   SetInj of set_injection reg
 
 and set_injection = {
-  opening    : kwd_set;
+  opening    : opening;
-  elements   : (expr, semi) nsepseq;
+  elements   : (expr, semi) sepseq;
   terminator : semi option;
-  closing    : kwd_end
+  closing    : closing
 }
 
+and opening =
+  Kwd        of keyword
+| KwdBracket of keyword * lbracket
+
+and closing =
+  End       of kwd_end
+| RBracket  of rbracket
+
 and map_expr =
   MapLookUp of map_lookup reg
 | MapInj    of map_injection reg
@@ -566,8 +577,21 @@ and string_expr =
 
 and list_expr =
   Cons of cons bin_op reg
-| List      of (expr, comma) nsepseq brackets reg
+| List of list_injection reg
-| EmptyList of empty_list reg
+| Nil  of nil par reg
+
+and list_injection = {
+  opening    : opening;
+  elements   : (expr, semi) sepseq;
+  terminator : semi option;
+  closing    : closing
+}
+
+and nil = {
+  nil       : kwd_nil;
+  colon     : colon;
+  list_type : type_expr
+}
 
 and constr_expr =
   SomeApp   of (c_Some * arguments) reg
@@ -599,15 +623,6 @@ and record_projection = {
 
 and tuple = (expr, comma) nsepseq par reg
 
-and empty_list = typed_empty_list par
-
-and typed_empty_list = {
-  lbracket  : lbracket;
-  rbracket  : rbracket;
-  colon     : colon;
-  list_type : type_expr
-}
-
 and none_expr = typed_none_expr par
 
 and typed_none_expr = {

LexToken.mli

@@ -82,8 +82,10 @@ type t =
 | If         of Region.t  (* "if"         *)
 | In         of Region.t  (* "in"         *)
 | Is         of Region.t  (* "is"         *)
+| List       of Region.t  (* "list"       *)
 | Map        of Region.t  (* "map"        *)
 | Mod        of Region.t  (* "mod"        *)
+| Nil        of Region.t  (* "nil"        *)
 | Not        of Region.t  (* "not"        *)
 | Of         of Region.t  (* "of"         *)
 | Or         of Region.t  (* "or"         *)

LexToken.mll

@@ -81,8 +81,10 @@ type t =
 | If         of Region.t  (* "if"         *)
 | In         of Region.t  (* "in"         *)
 | Is         of Region.t  (* "is"         *)
+| List       of Region.t  (* "list"       *)
 | Map        of Region.t  (* "map"        *)
 | Mod        of Region.t  (* "mod"        *)
+| Nil        of Region.t  (* "nil"        *)
 | Not        of Region.t  (* "not"        *)
 | Of         of Region.t  (* "of"         *)
 | Or         of Region.t  (* "or"         *)
@@ -206,8 +208,10 @@ let proj_token = function
 | If         region -> region, "If"
 | In         region -> region, "In"
 | Is         region -> region, "Is"
+| List       region -> region, "List"
 | Map        region -> region, "Map"
 | Mod        region -> region, "Mod"
+| Nil        region -> region, "Nil"
 | Not        region -> region, "Not"
 | Of         region -> region, "Of"
 | Or         region -> region, "Or"
@@ -286,22 +290,23 @@ let to_lexeme = function
 | Const      _ -> "const"
 | Contains   _ -> "contains"
 | Down       _ -> "down"
-| Fail       _ -> "fail"
+| Else       _ -> "else"
-| If         _ -> "if"
+| End        _ -> "end"
-| In         _ -> "in"
-| Is         _ -> "is"
 | Entrypoint _ -> "entrypoint"
+| Fail       _ -> "fail"
 | For        _ -> "for"
 | From       _ -> "from"
 | Function   _ -> "function"
-| Type       _ -> "type"
+| If         _ -> "if"
+| In         _ -> "in"
+| Is         _ -> "is"
+| List       _ -> "list"
+| Map        _ -> "map"
+| Mod        _ -> "mod"
+| Nil        _ -> "nil"
+| Not        _ -> "not"
 | Of         _ -> "of"
 | Or         _ -> "or"
-| Var        _ -> "var"
-| End        _ -> "end"
-| Then       _ -> "then"
-| Else       _ -> "else"
-| Map        _ -> "map"
 | Patch      _ -> "patch"
 | Procedure  _ -> "procedure"
 | Record     _ -> "record"
@@ -310,9 +315,10 @@ let to_lexeme = function
 | Skip       _ -> "skip"
 | Step       _ -> "step"
 | Storage    _ -> "storage"
+| Then       _ -> "then"
 | To         _ -> "to"
-| Mod        _ -> "mod"
+| Type       _ -> "type"
-| Not        _ -> "not"
+| Var        _ -> "var"
 | While      _ -> "while"
 | With       _ -> "with"
 
@@ -346,22 +352,23 @@ let keywords = [
   (fun reg -> Const      reg);
   (fun reg -> Contains   reg);
   (fun reg -> Down       reg);
-  (fun reg -> Fail       reg);
+  (fun reg -> Else       reg);
-  (fun reg -> If         reg);
+  (fun reg -> End        reg);
-  (fun reg -> In         reg);
-  (fun reg -> Is         reg);
   (fun reg -> Entrypoint reg);
   (fun reg -> For        reg);
   (fun reg -> From       reg);
   (fun reg -> Function   reg);
-  (fun reg -> Type       reg);
+  (fun reg -> Fail       reg);
+  (fun reg -> If         reg);
+  (fun reg -> In         reg);
+  (fun reg -> Is         reg);
+  (fun reg -> List       reg);
+  (fun reg -> Map        reg);
+  (fun reg -> Mod        reg);
+  (fun reg -> Nil        reg);
+  (fun reg -> Not        reg);
   (fun reg -> Of         reg);
   (fun reg -> Or         reg);
-  (fun reg -> Var        reg);
-  (fun reg -> End        reg);
-  (fun reg -> Then       reg);
-  (fun reg -> Else       reg);
-  (fun reg -> Map        reg);
   (fun reg -> Patch      reg);
   (fun reg -> Procedure  reg);
   (fun reg -> Record     reg);
@@ -370,9 +377,10 @@ let keywords = [
   (fun reg -> Skip       reg);
   (fun reg -> Step       reg);
   (fun reg -> Storage    reg);
+  (fun reg -> Then       reg);
   (fun reg -> To         reg);
-  (fun reg -> Mod        reg);
+  (fun reg -> Type       reg);
-  (fun reg -> Not        reg);
+  (fun reg -> Var        reg);
   (fun reg -> While      reg);
   (fun reg -> With       reg)
 ]
@@ -574,22 +582,23 @@ let is_kwd = function
 | Const      _
 | Contains   _
 | Down       _
-| Fail       _
+| Else       _
-| If         _
+| End        _
-| In         _
-| Is         _
 | Entrypoint _
+| Fail       _
 | For        _
 | From       _
 | Function   _
-| Type       _
+| If         _
+| In         _
+| Is         _
+| List       _
+| Map        _
+| Mod        _
+| Nil        _
+| Not        _
 | Of         _
 | Or         _
-| Var        _
-| End        _
-| Then       _
-| Else       _
-| Map        _
 | Patch      _
 | Procedure  _
 | Record     _
@@ -598,9 +607,10 @@ let is_kwd = function
 | Skip       _
 | Step       _
 | Storage    _
+| Then       _
 | To         _
-| Mod        _
+| Type       _
-| Not        _
+| Var        _
 | While      _
 | With       _ -> true
 |            _ -> false

ParToken.mly

@@ -49,22 +49,23 @@
 %token <Region.t> Const       (* "const"      *)
 %token <Region.t> Contains    (* "contains"   *)
 %token <Region.t> Down        (* "down"       *)
+%token <Region.t> Else        (* "else"       *)
+%token <Region.t> End         (* "end"        *)
+%token <Region.t> Entrypoint  (* "entrypoint" *)
 %token <Region.t> Fail        (* "fail"       *)
+%token <Region.t> For         (* "for"        *)
+%token <Region.t> Function    (* "function"   *)
 %token <Region.t> From        (* "from"       *)
 %token <Region.t> If          (* "if"         *)
 %token <Region.t> In          (* "in"         *)
 %token <Region.t> Is          (* "is"         *)
-%token <Region.t> Entrypoint  (* "entrypoint" *)
+%token <Region.t> List        (* "list"       *)
-%token <Region.t> For         (* "for"        *)
+%token <Region.t> Map         (* "map"        *)
-%token <Region.t> Function    (* "function"   *)
+%token <Region.t> Mod         (* "mod"        *)
-%token <Region.t> Type        (* "type"       *)
+%token <Region.t> Nil         (* "nil"        *)
+%token <Region.t> Not         (* "not"        *)
 %token <Region.t> Of          (* "of"         *)
 %token <Region.t> Or          (* "or"         *)
-%token <Region.t> Var         (* "var"        *)
-%token <Region.t> End         (* "end"        *)
-%token <Region.t> Then        (* "then"       *)
-%token <Region.t> Else        (* "else"       *)
-%token <Region.t> Map         (* "map"        *)
 %token <Region.t> Patch       (* "patch"      *)
 %token <Region.t> Procedure   (* "procedure"  *)
 %token <Region.t> Record      (* "record"     *)
@@ -73,9 +74,10 @@
 %token <Region.t> Skip        (* "skip"       *)
 %token <Region.t> Step        (* "step"       *)
 %token <Region.t> Storage     (* "storage"    *)
+%token <Region.t> Then        (* "then"       *)
 %token <Region.t> To          (* "to"         *)
-%token <Region.t> Mod         (* "mod"        *)
+%token <Region.t> Type        (* "type"       *)
-%token <Region.t> Not         (* "not"        *)
+%token <Region.t> Var         (* "var"        *)
 %token <Region.t> While       (* "while"      *)
 %token <Region.t> With        (* "with"       *)
 

Parser.mly

@@ -177,6 +177,13 @@ core_type:
     let tuple = {region; value={lpar; inside=inside,[]; rpar}}
     in TApp {region=total; value = type_constr, tuple}
   }
+| List par(type_expr) {
+    let total = cover $1 $2.region in
+    let type_constr = {value="list"; region=$1} in
+    let {region; value = {lpar; inside; rpar}} = $2 in
+    let tuple = {region; value={lpar; inside=inside,[]; rpar}}
+    in TApp {region=total; value = type_constr, tuple}
+  }
 | par(type_expr) {
     TPar $1
   }
@@ -390,18 +397,17 @@ unqualified_decl(OP):
     let init =
       match $5.value with
         `Expr e -> e
-      | `EList (lbracket, rbracket) ->
+      | `EList kwd_nil ->
            let region = $5.region
            and value = {
-             lbracket;
+             nil = kwd_nil;
-             rbracket;
              colon = Region.ghost;
              list_type = $3} in
            let value = {
              lpar   = Region.ghost;
              inside = value;
              rpar   = Region.ghost} in
-           EList (EmptyList {region; value})
+           EList (Nil {region; value})
       | `ENone region ->
            let value = {
              lpar = Region.ghost;
@@ -453,8 +459,7 @@ var_decl:
 extended_expr:
   expr          { {region = expr_to_region $1;
                    value  = `Expr $1} }
-| LBRACKET RBRACKET { {region = cover $1 $2;
+| Nil           { {region = $1; value = `EList $1} }
-                       value  = `EList ($1,$2)} }
 | C_None        { {region = $1; value = `ENone $1} }
 | map_injection { {region = $1.region; value = `EMap $1} }
 | set_injection { {region = $1.region; value = `ESet $1} }
@@ -527,11 +532,39 @@ set_injection:
   Set series(expr,End) {
     let first, (others, terminator, closing) = $2 in
     let region = cover $1 closing
-    and value = {
+    and value : set_injection = {
-      opening  = $1;
+      opening  = Kwd $1;
-      elements = first, others;
+      elements = Some (first, others);
       terminator;
-      closing}
+      closing = End closing}
+    in {region; value}
+  }
+| Set End {
+    let region = cover $1 $2
+    and value : set_injection = {
+      opening    = Kwd $1;
+      elements   = None;
+      terminator = None;
+      closing    = End $2}
+    in {region; value}
+  }
+| Set LBRACKET series(expr,RBRACKET) {
+    let first, (others, terminator, closing) = $3 in
+    let region = cover $1 closing
+    and value : set_injection = {
+      opening  = KwdBracket ($1,$2);
+      elements = Some (first, others);
+      terminator;
+      closing = RBracket closing}
+    in {region; value}
+  }
+| Set LBRACKET RBRACKET {
+    let region = cover $1 $3
+    and value : set_injection = {
+      opening    = KwdBracket ($1,$2);
+      elements   = None;
+      terminator = None;
+      closing    = RBracket $3}
     in {region; value}
   }
 
@@ -540,10 +573,38 @@ map_injection:
     let first, (others, terminator, closing) = $2 in
     let region = cover $1 closing
     and value = {
-      opening  = $1;
+      opening  = Kwd $1;
-      bindings = first, others;
+      bindings = Some (first, others);
       terminator;
-      closing}
+      closing = End closing}
+    in {region; value}
+  }
+| Map End {
+    let region = cover $1 $2
+    and value = {
+      opening    = Kwd $1;
+      bindings   = None;
+      terminator = None;
+      closing    = End $2}
+    in {region; value}
+  }
+| Map LBRACKET series(binding,RBRACKET) {
+    let first, (others, terminator, closing) = $3 in
+    let region = cover $1 closing
+    and value = {
+      opening  = KwdBracket ($1,$2);
+      bindings = Some (first, others);
+      terminator;
+      closing = RBracket closing}
+    in {region; value}
+  }
+| Map LBRACKET RBRACKET {
+    let region = cover $1 $3
+    and value  = {
+      opening    = KwdBracket ($1,$2);
+      bindings   = None;
+      terminator = None;
+      closing    = RBracket $3}
     in {region; value}
   }
 
@@ -873,7 +934,7 @@ core_expr:
 | C_Unit           { EUnit $1 }
 | tuple            { ETuple $1 }
 | list_expr        { EList (List $1) }
-| empty_list       { EList (EmptyList $1) }
+| nil              { EList (Nil $1) }
 | none_expr        { EConstr (NoneExpr $1) }
 | fun_call         { ECall $1 }
 | map_expr         { EMap $1 }
@@ -953,17 +1014,53 @@ arguments:
   tuple { $1 }
 
 list_expr:
-  brackets(nsepseq(expr,COMMA)) { $1 }
+  List series(expr,End) {
+    let first, (others, terminator, closing) = $2 in
+    let region = cover $1 closing
+    and value : list_injection = {
+      opening  = Kwd $1;
+      elements = Some (first, others);
+      terminator;
+      closing = End closing}
+    in {region; value}
+  }
+| List End {
+    let region = cover $1 $2
+    and value : list_injection = {
+      opening    = Kwd $1;
+      elements   = None;
+      terminator = None;
+      closing    = End $2}
+    in {region; value}
+  }
+| List LBRACKET series(expr,RBRACKET) {
+    let first, (others, terminator, closing) = $3 in
+    let region = cover $1 closing
+    and value : list_injection = {
+      opening  = KwdBracket ($1,$2);
+      elements = Some (first, others);
+      terminator;
+      closing = RBracket closing}
+    in {region; value}
+  }
+| List LBRACKET RBRACKET {
+    let region = cover $1 $3
+    and value : list_injection = {
+      opening    = KwdBracket ($1,$2);
+      elements   = None;
+      terminator = None;
+      closing    = RBracket $3}
+    in {region; value}
+  }
 
-empty_list:
+nil:
   par(typed_empty_list) { $1 }
 
 typed_empty_list:
-  LBRACKET RBRACKET COLON type_expr {
+  Nil COLON type_expr {
-    {lbracket  = $1;
+    {nil       = $1;
-     rbracket  = $2;
+     colon     = $2;
-     colon     = $3;
+     list_type = $3}
-     list_type = $4}
   }
 
 none_expr:

Tests/crowdfunding.ligo

@@ -10,7 +10,9 @@ entrypoint contribute (storage store : store;
                        const sender  : address;
                        const amount  : mutez)
   : store * list (operation) is
-  var operations : list (operation) := []
+  var operations : list (operation) := nil
+  const s : list (int) = list [1; 2; 3]
+  const t : set (int) = set []
   block {
     if now > store.deadline then
       fail "Deadline passed";
@@ -24,14 +26,14 @@ entrypoint contribute (storage store : store;
 
 entrypoint withdraw (storage store : store; const sender : address)
   : store * list (operation) is
-  var operations : list (operation) := []
+  var operations : list (operation) := list end
   begin
     if sender = owner then
       if now (Unit) >= store.deadline then
         if balance >= store.goal then {
              store.funded := True;
 //           patch store with record funded = True end;
-             operations := [Transfer (owner, balance)];
+             operations := list [Transfer (owner, balance)];
         };
         else fail "Below target"
       else { fail "Too soon"; }
@@ -40,7 +42,7 @@ entrypoint withdraw (storage store : store; const sender : address)
 
 entrypoint claim (storage store : store; const sender : address)
   : store * list (operation) is
-  var operations : list (operation) := []
+  var operations : list (operation) := list []
   var amount : mutez := 0
   begin
     if now <= store.deadline then
@@ -54,7 +56,7 @@ entrypoint claim (storage store : store; const sender : address)
             fail "Cannot refund"
           else
             begin
-              operations := [Transfer (sender, amount)];
+              operations := list [Transfer (sender, amount)];
               remove sender from map store.backers
             end
       end