From 9339ae44a89f295523b6c25681d87642767864c4 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 26 May 2019 00:52:33 +0300
Subject: [PATCH] Make all components of a for loop optional

---
 source/programcompiler.cpp | 22 ++++++++++++++++------
 source/programparser.cpp   | 15 ++++++++++-----
 source/programsyntax.cpp   |  3 ++-
 3 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/source/programcompiler.cpp b/source/programcompiler.cpp
index a3691b11..88ec6e59 100644
--- a/source/programcompiler.cpp
+++ b/source/programcompiler.cpp
@@ -544,12 +544,22 @@ void ProgramCompiler::Formatter::visit(Conditional &cond)
 void ProgramCompiler::Formatter::visit(Iteration &iter)
 {
 	formatted += "for(";
-	iter.init_statement->visit(*this);
-	formatted += ' ';
-	iter.condition->visit(*this);
-	formatted += "; ";
-	iter.loop_expression->visit(*this);
-	formatted += ")\n";
+	if(iter.init_statement)
+		iter.init_statement->visit(*this);
+	else
+		formatted += ';';
+	if(iter.condition)
+	{
+		formatted += ' ';
+		iter.condition->visit(*this);
+	}
+	formatted += ';';
+	if(iter.loop_expression)
+	{
+		formatted += ' ';
+		iter.loop_expression->visit(*this);
+	}
+	formatted += ')';
 	iter.body.visit(*this);
 }
 
diff --git a/source/programparser.cpp b/source/programparser.cpp
index 3b87ea7b..b607e1cf 100644
--- a/source/programparser.cpp
+++ b/source/programparser.cpp
@@ -853,14 +853,19 @@ RefPtr<Iteration> ProgramParser::parse_iteration()
 		loop->init_statement = parse_statement();
 	else
 	{
-		RefPtr<ExpressionStatement> expr = new ExpressionStatement;
-		expr->expression = parse_expression();
+		if(token!=";")
+		{
+			RefPtr<ExpressionStatement> expr = new ExpressionStatement;
+			expr->expression = parse_expression();
+			loop->init_statement = expr;
+		}
 		expect(";");
-		loop->init_statement = expr;
 	}
-	loop->condition = parse_expression();
+	if(peek_token()!=";")
+		loop->condition = parse_expression();
 	expect(";");
-	loop->loop_expression = parse_expression();
+	if(peek_token()!=")")
+		loop->loop_expression = parse_expression();
 	expect(")");
 
 	parse_block(loop->body, false);
diff --git a/source/programsyntax.cpp b/source/programsyntax.cpp
index 8cb276d9..47b59f6c 100644
--- a/source/programsyntax.cpp
+++ b/source/programsyntax.cpp
@@ -290,7 +290,8 @@ void TraversingVisitor::visit(Conditional &cond)
 
 void TraversingVisitor::visit(Iteration &iter)
 {
-	iter.init_statement->visit(*this);
+	if(iter.init_statement)
+		iter.init_statement->visit(*this);
 	if(iter.condition)
 		iter.condition->visit(*this);
 	if(iter.loop_expression)
-- 
2.43.0