✨ Parser support for while loops

Author: igorkulman

PascalInterpreter/PascalInterpreter/Lexer/Lexer.swift

@@ -43,7 +43,7 @@ public class Lexer {
         "FOR": .for,
         "TO": .to,
         "DO": .do,
-        "WHILE": .while
+        "WHILE": .while,
     ]
 
     public init(_ text: String) {

PascalInterpreter/PascalInterpreter/Parser/Parser.swift

@@ -279,6 +279,7 @@ public class Parser {
      | assignment_statement
      | repeat_until
      | for_loop
+     | while_loop
      | empty
      */
     private func statement() -> AST {
@@ -289,6 +290,8 @@ public class Parser {
             return ifElseStatement()
         case .repeat:
             return repeatUntilLoop()
+        case .while:
+            return whileLoop()
         case .for:
             return forLoop()
         case .id:
@@ -323,6 +326,19 @@ public class Parser {
         return RepeatUntil(statement: statements.count == 1 ? statements[0] : Compound(children: statements), condition: condition)
     }
 
+    /**
+     Rule:
+
+     for_loop : WHILE condition DO statement
+     */
+    private func whileLoop() -> While {
+        eat(.while)
+        let condition = self.condition()
+        eat(.do)
+        let statement = self.statement()
+        return While(statement: statement, condition: condition)
+    }
+
     /**
      Rule:
 

PascalInterpreter/PascalInterpreterTests/ParserTests.swift

@@ -469,4 +469,27 @@ class ParserTests: XCTestCase {
         let node = Program(name: "Main", block: block)
         XCTAssertEqual(result, node)
     }
+
+    func testProgramWithWhileLoop() {
+        let program =
+            """
+            program Main;
+            var x: integer;
+
+            begin
+            x:=0;
+            while x < 6 do
+                x:=x+1;
+            writeln(x);
+            end.  { Main }
+            """
+
+        let parser = Parser(program)
+        let result = parser.parse()
+        let xDec = VariableDeclaration(variable: Variable(name: "x"), type: VariableType(type: .integer))
+        let compound = Compound(children: [Assignment(left: Variable(name: "x"), right: Number.integer(0)), While(statement: Assignment(left: Variable(name: "x"), right: BinaryOperation(left: Variable(name: "x"), operation: BinaryOperationType.plus, right: Number.integer(1))), condition: Condition(type: .lessThan, leftSide: Variable(name: "x"), rightSide: Number.integer(6))), FunctionCall(name: "writeln", actualParameters: [Variable(name: "x")]), NoOp()])
+        let block = Block(declarations: [xDec], compound: compound)
+        let node = Program(name: "Main", block: block)
+        XCTAssertEqual(result, node)
+    }
 }

PascalInterpreter/PascalInterpreterTests/XCTestCase+FatalError.swift

@@ -137,6 +137,9 @@ func XCTAssertEqual(_ left: AST, _ right: AST) {
     case let (left as RepeatUntil, right as RepeatUntil):
         XCTAssertEqual(left.condition, right.condition)
         XCTAssertEqual(left.statement, right.statement)
+    case let (left as While, right as While):
+        XCTAssertEqual(left.condition, right.condition)
+        XCTAssertEqual(left.statement, right.statement)
     case let (left as For, right as For):
         XCTAssertEqual(left.variable, right.variable)
         XCTAssertEqual(left.startValue, right.startValue)