From 84a888738a32ed13081b35fda0d11f3d2d79de30 Mon Sep 17 00:00:00 2001
From: Brandon Dyck <brandon@dyck.us>
Date: Wed, 28 Jun 2023 17:18:31 -0600
Subject: [PATCH] Parse sequencing expressions

---
 ASTPrinter.cs   |  5 +++++
 Expr.g.cs       | 10 ++++++++++
 Parser.cs       |  8 +++++++-
 Program.cs      |  2 ++
 ast_classes.fsx |  4 +++-
 grammar.txt     | 22 +++++++++++-----------
 6 files changed, 38 insertions(+), 13 deletions(-)

diff --git a/ASTPrinter.cs b/ASTPrinter.cs
index a331171..9017e36 100644
--- a/ASTPrinter.cs
+++ b/ASTPrinter.cs
@@ -48,4 +48,9 @@ class ASTPrinter : IVisitor<string>
 	{
 		return parenthesize("if", expr.Condition, expr.Then, expr.Else);
 	}
+
+	public string visitSequenceExpr(Sequence expr)
+	{
+		return parenthesize("seq", expr.Left, expr.Right);
+	}
 }
diff --git a/Expr.g.cs b/Expr.g.cs
index 1e0937d..d743ae9 100644
--- a/Expr.g.cs
+++ b/Expr.g.cs
@@ -10,12 +10,22 @@ public abstract class Expr {
 	public abstract T accept<T>(IVisitor<T> visitor);
 }
 public interface IVisitor<T> {
+	T visitSequenceExpr(Sequence expr);
 	T visitBinaryExpr(Binary expr);
 	T visitGroupingExpr(Grouping expr);
 	T visitLiteralExpr(Literal expr);
 	T visitUnaryExpr(Unary expr);
 	T visitIfExpr(If expr);
 }
+public class Sequence : Expr
+{
+	public required Expr Left { get; init; }
+	public required Expr Right { get; init; }
+	public override T accept<T>(IVisitor<T> visitor)
+	{
+		return visitor.visitSequenceExpr(this);
+	}
+}
 public class Binary : Expr
 {
 	public required Expr Left { get; init; }
diff --git a/Parser.cs b/Parser.cs
index e0efae7..c9f0098 100644
--- a/Parser.cs
+++ b/Parser.cs
@@ -121,7 +121,13 @@ class Parser
 
 	private Expr expression()
 	{
-		return equality();
+		var expr = equality();
+		while (match(TokenType.Semicolon))
+		{
+			var right = equality();
+			expr = new Sequence { Left = expr, Right = right };
+		}
+		return expr;
 	}
 
 	private Expr equality()
diff --git a/Program.cs b/Program.cs
index efbc2dd..2e01266 100644
--- a/Program.cs
+++ b/Program.cs
@@ -94,6 +94,7 @@ public enum TokenType
 	Backtick,
 	At,
 	Comma,
+	Semicolon,
 	Period,
 	Equal,
 	Plus, Minus, Asterisk, Slash,
@@ -284,6 +285,7 @@ class Scanner
 			case '`': addToken(TokenType.Backtick); break;
 			case '@': addToken(TokenType.At); break;
 			case ',': addToken(TokenType.Comma); break;
+			case ';': addToken(TokenType.Semicolon); break;
 			case '.': addToken(TokenType.Period); break;
 			case '*': addToken(TokenType.Asterisk); break;
 			case '/': addToken(TokenType.Slash); break;
diff --git a/ast_classes.fsx b/ast_classes.fsx
index 35ec3ed..5ecb21a 100644
--- a/ast_classes.fsx
+++ b/ast_classes.fsx
@@ -2,7 +2,9 @@ type Field = { Type: string; Name: string }
 type Type = { Name: string; Fields: list<Field> }
 
 let types =
-    [ { Name = "Binary"
+    [ { Name = "Sequence"
+        Fields = [ { Type = "Expr"; Name = "Left" }; { Type = "Expr"; Name = "Right" } ] }
+      { Name = "Binary"
         Fields =
           [ { Type = "Expr"; Name = "Left" }
             { Type = "Token"; Name = "Op" }
diff --git a/grammar.txt b/grammar.txt
index ac1dce0..f26d7a9 100644
--- a/grammar.txt
+++ b/grammar.txt
@@ -1,20 +1,16 @@
 expression ->
-	| literal
-//	| identifier
-//	| sequence
+	| sequence
+//	| apply
 	| unary
 	| binary
 //	| let
-//	| when
-	| if
-	| variant
-	| record
-	| list
+	| compound
+	| control
 	| field
 	| index
-	| grouping ;
+//	| identifier
+	| primary
 
-literal -> NUMBER | STRING ;
 identifier -> IDENTIFIER | "@" STRING ;
 grouping -> "(" expression ")" ;
 unary -> ( "-" | "!" ) expression ;
@@ -24,11 +20,15 @@ operator ->
 	| "+" | "-" | "*" | "/"
 //	| "|>" | "<|" | ">>" | "<<"
 	| "++" ;
+control ->
+	| if
+//	| when
 if -> "if" expression "then" expression "else" expression ;
+compound -> variant | record | list ;
 variant -> "`" identifier ( "(" ( expression ( "," expression)* )? ")" )? ;
 record ->
 	"{" ( identifier "=" expression ( "," identifier "=" expression )* )? "}" ;
 list -> "[" ( expression ( "," expression )* )? "]" ;
 field -> expression "." identifier ;
 index -> expression "[" expression "]" ;
-grouping -> "(" expression ")" ;
+primary -> NUMBER | STRING | "(" expression ")" ;