From 9d2fc31eaee986a4ee89d8ac9952867ba8b9d8d3 Mon Sep 17 00:00:00 2001
From: Aaro Koivukangas <aaro.koivukangas@gmail.com>
Date: Sat, 28 Feb 2026 15:55:08 +0200
Subject: [PATCH] Add while-do and declarations

---
 compiler/src/main/scala/Parser.scala      | 25 ++++++++-
 compiler/src/test/scala/ParserTests.scala | 63 +++++++++++++++++++++++
 2 files changed, 87 insertions(+), 1 deletion(-)

diff --git a/compiler/src/main/scala/Parser.scala b/compiler/src/main/scala/Parser.scala
index 6b7af71..a01cc85 100644
--- a/compiler/src/main/scala/Parser.scala
+++ b/compiler/src/main/scala/Parser.scala
@@ -21,7 +21,13 @@ case class UnaryOperator(operator: String, expr: Expression) extends Expression
   override def toString: String = s"UnaryOperator($operator: $expr)"
 }
 case class IfThenElse(condition: Expression, body: Expression, elseBody: Option[Expression]) extends Expression {
-  override def toString: String = s"If($condition then $body)"
+  override def toString: String = s"If($condition then $body, else $elseBody)"
+}
+case class WhileDo(condition: Expression, body: Expression) extends Expression {
+  override def toString: String = s"While($condition do $body)"
+}
+case class Declaration(name: Identifier, body: Expression) extends Expression {
+  override def toString: String = s"Var($name = $body)"
 }
 case class Function(name: String, arguments: List[Expression]) extends Expression {
   override def toString: String = s"Function($name(${arguments.mkString(", ")}))"
@@ -110,6 +116,7 @@ class Parser(tokens: List[Token]):
     return token.tokenType match {
       case TokenType.IntLiteral => parseIntLiteral()
       case TokenType.Identifier if token.value == "if" => parseIfThenElse()
+      case TokenType.Identifier if token.value == "while" => parseWhileDo()
       case TokenType.Identifier if token.value == "not" => parseUnaryOperator()
       case TokenType.Identifier => parseIdentifier()
       case TokenType.Operator if token.value == "-" => parseUnaryOperator()
@@ -131,6 +138,14 @@ class Parser(tokens: List[Token]):
     return IfThenElse(condition, body, elseBody)
 
 
+  def parseWhileDo(): Expression =
+    consume(Some("while")).get
+    val condition = parseExpression()
+    consume(Some("do")).get
+    val body = parseExpression()
+    return WhileDo(condition, body)
+
+
   def parseFunction(parsedFnName: Option[String] = None): Expression =
     val fnName = parsedFnName.getOrElse(consume(Some(TokenType.Identifier)).get.value)
     consume(Some("(")).get
@@ -160,6 +175,13 @@ class Parser(tokens: List[Token]):
     return right
 
 
+  def parseDeclaration(): Expression =
+    val name = parseIdentifier()
+    consume(Some("=")).get
+    val body = parseExpression()
+    return Declaration(name, body)
+
+
   def parseExpression(initialDepth: Int = 0): Expression =
     var depth = initialDepth
     var left = parseFactor()
@@ -167,6 +189,7 @@ class Parser(tokens: List[Token]):
     // If identifier is followed by ( => it is a function call (or syntax error :D)
     left = left match {
       case left: Identifier if peek().value == "(" => parseFunction(Some(left.name))
+      case left: Identifier if left.name == "var" => parseDeclaration()
       case left if peek().value == "=" => parseEquals(Some(left))
       case _ => left
     }
diff --git a/compiler/src/test/scala/ParserTests.scala b/compiler/src/test/scala/ParserTests.scala
index 33fa642..eedc4d9 100644
--- a/compiler/src/test/scala/ParserTests.scala
+++ b/compiler/src/test/scala/ParserTests.scala
@@ -560,3 +560,66 @@ class ParserEqualTests extends BaseParserTests {
     assertEquals(result, expected)
   }
 }
+
+
+class ParseWhileDoTests extends BaseParserTests {
+  test("should parse simple while do") {
+    val p = testParser("while true do print()")
+    val result = p.parseExpression()
+    val expected = WhileDo(Identifier("true"), Function("print", List()))
+
+    assertEquals(result, expected)
+  }
+  test("should parse while do with expressions") {
+    val p = testParser("while i+3 <= x do parse_bool(true) != false")
+    val result = p.parseExpression()
+    val expected = WhileDo(
+      BinaryOperator(
+        BinaryOperator(Identifier("i"), "+", Literal(3)),
+        "<=",
+        Identifier("x")
+      ),
+      BinaryOperator(Function("parse_bool", List(Identifier("true"))), "!=", Identifier("false"))
+    )
+
+    assertEquals(result, expected)
+  }
+}
+
+
+class ParserDeclarationTests extends BaseParserTests {
+  test("should parse simple declaration") {
+    val p = testParser("var x = 1")
+    val result = p.parseExpression()
+    val expected = Declaration(Identifier("x"), Literal(1))
+
+    assertEquals(result, expected)
+  }
+  test("should parse declaration with expression body") {
+    val p = testParser("var result = parse(1+x)")
+    val result = p.parseExpression()
+    val expected = Declaration(
+      Identifier("result"),
+      Function("parse", List(BinaryOperator(Literal(1), "+", Identifier("x"))))
+     )
+
+    assertEquals(result, expected)
+  }
+
+  test("should not parse declaration with non-identifier name") {
+    val token = Tokenizer.tokenize("var x>").get(2)
+    // var (1+1) is function...
+    val p = testParser("var x>y = parse(1+x)")
+    interceptMessage[java.lang.Exception](s"Token $token was not expected: =") {
+      val result = p.parseExpression()
+    }
+  }
+  test("should not parse declaration with non-identifier name (function)".fail) {
+    val token = Tokenizer.tokenize("var (").get(1)
+    // var (1+1) is function...
+    val p = testParser("var (1+1) = parse(1+x)")
+    interceptMessage[java.lang.Exception](s"Token $token was not expected: Identifier") {
+      val result = p.parseExpression()
+    }
+  }
+}