Add operators to EC# parser/printer: <=>, |>, ?|> (#113)

Core/Loyc.Syntax/CodeSymbols.cs

@@ -51,6 +51,7 @@ public partial class CodeSymbols
 		public static readonly Symbol LT = GSymbol.Get("'<");     //!< "<"  Less-than operator
 		public static readonly Symbol LE = GSymbol.Get("'<=");    //!< "<=" Less-than-or-equal-to operator
 		public static readonly Symbol Matches = GSymbol.Get("'=~");    //!< "=~" Pattern match test operator
+		public static readonly Symbol Compare = GSymbol.Get("'<=>");    //!< "<=>" Three-way comparison a.k.a. shaceship operator
 		public static readonly Symbol Shr = GSymbol.Get("'>>");   //!< ">>" Right-shift operator
 		public static readonly Symbol Shl = GSymbol.Get("'<<");   //!< "<<" Left-shift operator
 		public static readonly Symbol Not = GSymbol.Get("'!");    //!< "!"  Logical 'not' operator

Main/Ecs/EcsCodeSymbols.cs

@@ -19,8 +19,12 @@ public class EcsCodeSymbols : Loyc.Syntax.CodeSymbols
 		public static new readonly Symbol Async = GSymbol.Get("#async"); //!< [#async] Task Foo(); <=> async Task Foo();
 																	 // async is a normal contextual attribute so it needs no special parser support.
 		public static new readonly Symbol Await = GSymbol.Get("await"); //!< await(x); <=> await x; (TENTATIVE: should this be changed to #await?)
-		public static new readonly Symbol InitializerAssignment = GSymbol.Get("'[]="); //!< @`[]=`(0, 1, x) <=> [0, 1]=x
-																				   // (TENTATIVE, and only supported in 'new' initializer blocks)
+		public static new readonly Symbol InitializerAssignment = GSymbol.Get("'[]="); //!< @`'[]=`(0, 1, x) <=> [0, 1]=x
+																					   // (TENTATIVE, and only supported in 'new' initializer blocks)
+
+		// Proposed: https://github.com/dotnet/csharplang/issues/74
+		public static readonly Symbol ForwardPipeArrow = GSymbol.Get("'|>"); //!< @`'|>`(a, b) <=> a |> b
+		public static readonly Symbol NullForwardPipeArrow = GSymbol.Get("'?|>"); //!< @`'?|>`(a, b) <=> a ?|> b
 
 		public static new readonly Symbol TriviaCsRawText = GSymbol.Get("%C#RawText");             //!< "%C#RawText" - `%C#RawText`("stuff") - Raw text that is only printed by the C# printer (not printers for other languages)
 		public static new readonly Symbol TriviaCsPPRawText = GSymbol.Get("%C#PPRawText");         //!< "%C#PPRawText" - `%C#PPRawText`("#stuff") - Raw text that is guaranteed to be preceded by a newline and is only printed by the C# printer

Main/Ecs/EcsPrecedence.cs

@@ -55,14 +55,15 @@ public static class EcsPrecedence
 		public static readonly Precedence Primary    = new Precedence(100);   // x.y x::y x=:y x->y f(x) x(->y) a[x] x++ x-- typeof() checked() unchecked() new
 		public static readonly Precedence NullDot    = new Precedence(99);    // ?.
 		public static readonly Precedence Prefix     = new Precedence(91, 90, 90, 91); // +  -  !  ~  ++x  --x  (T)x
-		public static readonly Precedence Power      = new Precedence(86, 85);// **
+		public static readonly Precedence Power      = new Precedence(85);    // ** (tentatively left-associative)
 		public static readonly Precedence Range      = new Precedence(80);    // ..
 		public static readonly Precedence Forward    = new Precedence(78);    // ==> x
 		public static readonly Precedence Switch     = new Precedence(75);    // expr switch { ... }
 		public static readonly Precedence Multiply   = new Precedence(70);    // *, /, %
 		public static readonly Precedence Add        = new Precedence(60);    // +, -, ~
 		public static readonly Precedence Shift      = new Precedence(56, 56, 56, 70); // >> << (for printing purposes, immiscible with * / + -)
 		public static readonly Precedence Backtick   = new Precedence(46, 72, 45, 73); // `custom operator` (immiscible with * / + - << >> ..)
+		public static readonly Precedence Compare3Way= new Precedence(42);    // <=>
 		public static readonly Precedence Compare    = new Precedence(40);    // < > <= >=
 		public static readonly Precedence IsAsUsing  = new Precedence(40, 99, 40, 40); // is as using
 		public static readonly new Precedence Equals = new Precedence(38);    // == != in
@@ -72,6 +73,7 @@ public static class EcsPrecedence
 		public static readonly Precedence And        = new Precedence(22);    // &&
 		public static readonly Precedence Or         = new Precedence(20);    // || ^^
 		public static readonly Precedence OrIfNull   = new Precedence(16);    // ??
+		public static readonly Precedence ForwardPipeArrow = new Precedence(13);    // |> ?|>
 		public static readonly Precedence IfElse     = new Precedence(11, 10, 10, 11); // x ? y : z
 		public static readonly Precedence Assign     = new Precedence(26,  0,  0, 1);  // =  *=  /=  %=  +=  -=  <<=  >>=  &=  ^=  |= ??= ~=
 		public static readonly Precedence Lambda     = new Precedence(85, -1, -2, -1); // =>

Main/Ecs/Parser/EcsLexerGrammar.les

@@ -187,20 +187,22 @@ namespace Loyc.Ecs.Parser
 		@[private] token At        @{ '@' { _type = TT.At;    _value = S.AtSign; } };
 
 		@[k(3), private] token Operator  @{
-		( "..."  { _type = TT.DotDot; _value = S.DotDotDot; }
-		/ "..<"  { _type = TT.DotDot; _value = S.DotDot; }
+		( "..." { _type = TT.DotDot; _value = S.DotDotDot; }
+		/ "..<" { _type = TT.DotDot; _value = S.DotDot; }
 		/ ".."  { _type = TT.DotDot; _value = S.DotDot; }
 		/ "."   { _type = TT.Dot; _value = S.Dot; }
 		| ">>=" { _type = TT.CompoundSet; _value = S.ShrAssign; }
 		/ ">="  { _type = TT.LEGE; _value = S.GE; }
 		/ ">"   { _type = TT.GT; _value = S.GT; }
+		/ "<=>" { _type = TT.Compare; _value = S.Compare; }
 		/ "<<=" { _type = TT.CompoundSet; _value = S.ShlAssign; }
 		/ "<="  { _type = TT.LEGE; _value = S.LE; }
 		/ "<"   { _type = TT.LT; _value = S.LT; }
 		| "&&"  { _type = TT.And; _value = S.And; }
 		/ "&="  { _type = TT.CompoundSet; _value = S.AndBitsAssign; }
 		/ "&"   { _type = TT.AndBits; _value = S.AndBits; }
-		| "||"  { _type = TT.OrXor; _value = S.Or; }
+		| "|>"  { _type = TT.PipeArrow; _value = S.ForwardPipeArrow; }
+		/ "||"  { _type = TT.OrXor; _value = S.Or; }
 		/ "|="  { _type = TT.CompoundSet; _value = S.OrBitsAssign; }
 		/ "|"   { _type = TT.OrBits; _value = S.OrBits; }
 		| "^^"  { _type = TT.OrXor; _value = S.Xor; }
@@ -236,6 +238,7 @@ namespace Loyc.Ecs.Parser
 		| "??=" { _type = TT.CompoundSet; _value = S.NullCoalesceAssign; }
 		/ "??"  { _type = TT.NullCoalesce; _value = S.NullCoalesce; }
 		/ "?."  { _type = TT.NullDot; _value = S.NullDot; }
+		/ "?|>" { _type = TT.PipeArrow; _value = S.NullForwardPipeArrow; }
 		/ "?"   { _type = TT.QuestionMark; _value = S.QuestionMark; }
 		| "$"   { _type = TT.Substitute; _value = S.Substitute; }
 		| "\\"  { _type = TT.Backslash; _value = S.Backslash; }