while loops

README.md

@@ -211,7 +211,8 @@ User {
 
 ### Control Flow
 
-Control flow in One is still quite limited, as the `for` keyword has not been implemented yet. `if`, `else` and `elif` statements are fully implemented and are written like this.
+Control flow in One isn't fully implemented yet, but it is already functional.
+`if`, `else` and `elif` statements are fully implemented and are written like this:
 
 ```
 let x int = 17;
@@ -225,7 +226,15 @@ if x >= 100 {
 }
 ```
 
-Using parentheses around the condition isn't necessary.
+`while` loops are very similar, and can be written like this:
+
+```
+let i int = 0;
+while i < 10 {
+    print(i);
+    i++;
+}
+```
 
 ### The main function
 

generator.v

@@ -1,3 +1,4 @@
+
 module main
 
 import strings
@@ -158,6 +159,12 @@ fn (mut g Generator) gen_stmt(stmt Stmt) {
 			g.out.write_string(') ')
 			g.gen_stmt(stmt.block)
 		}
+		WhileLoop {
+			g.out.write_string('while (')
+			g.gen_expr(stmt.guard)
+			g.out.write_string(') ')
+			g.gen_stmt(stmt.block)
+		}
 	}
 }
 

lexer.v

@@ -10,7 +10,7 @@ enum TokenType as u8 {
 	kw_if
 	kw_else
 	kw_elif
-	kw_for
+	kw_while
 	kw_break
 	kw_fn
 	kw_return
@@ -106,7 +106,7 @@ fn toktype_from_kw(kw string) TokenType {
 		'if' {.kw_if}
 		'else' {.kw_else}
 		'elif' {.kw_elif}
-		'for' {.kw_for}
+		'while' {.kw_while}
 		'break' {.kw_break}
 		'fn' {.kw_fn}
 		'return' {.kw_return}
@@ -133,7 +133,7 @@ fn is_real(str string) bool {
 
 fn is_keyword(str string) bool {
 	return [
-		"void", "int", "real", "bool", "string", "if", "else", "elif", "for", "break", "fn", "return", "let", "const", "true", "false", "print", "class", "immutable"
+		"void", "int", "real", "bool", "string", "if", "else", "elif", "while", "break", "fn", "return", "let", "const", "true", "false", "print", "class", "immutable"
 	].contains(str)
 }
 

parser.v

@@ -122,7 +122,9 @@ fn (mut s SymbolTable) is_in_global_scope() bool {
 
 // ------------------------------------------- Expressions
 
-type Expr = VoidExpr | UnaryExpr | BinaryExpr | IntegerLiteral | RealLiteral | BoolLiteral | StringLiteral | Variable | TypeExpr | Function | TypeCast | ParenExpr | PrintExpr | FnCall | ClassMember | ClassInstantiation | MemberAccess
+type Expr = VoidExpr | UnaryExpr | BinaryExpr | IntegerLiteral | RealLiteral | BoolLiteral | StringLiteral |
+						Variable | TypeExpr | Function | TypeCast | ParenExpr | PrintExpr | FnCall | ClassMember |
+						ClassInstantiation | MemberAccess
 
 struct VoidExpr {}
 
@@ -204,7 +206,8 @@ struct FnCall {
 
 // ------------------------------------------- Statements
 
-type Stmt = VarDecl | ExprStmt | ReturnStmt | Block | IfStmt | ElseStmt | ElifStmt | FuncDecl | Param | ClassDecl
+type Stmt = VarDecl | ExprStmt | ReturnStmt | Block | IfStmt | ElseStmt | ElifStmt | FuncDecl | Param |
+						ClassDecl | WhileLoop
 
 struct VarDecl {
 	name string
@@ -251,6 +254,11 @@ struct ElifStmt {
 	block Block
 }
 
+struct WhileLoop {
+	guard Expr
+	block Block
+}
+
 struct Param {
 	name string
 	type string
@@ -529,6 +537,10 @@ fn (mut p Parser) get_expr_is_immutable(expr Expr) bool {
 			memberinfo := classinfo.members_info[expr.member] or {parse_error("Undefined member ${expr.member}")}
 			memberinfo.is_immutable
 		}
+		Variable {
+			varinfo := p.symbols.lookup_var(expr.name) or {parse_error("Undefined variable ${expr.name}")}
+			varinfo.is_immutable
+		}
 		else {true}
 	}
 }
@@ -616,6 +628,7 @@ fn (mut p Parser) parse_statement() Stmt {
 			.kw_if     {return p.parse_if()}
 			.kw_else   {return p.parse_else()}
 			.kw_elif   {return p.parse_elif()}
+			.kw_while  {return p.parse_while()}
 			else       {return p.parse_expr_stmt()}
 		}
 }
@@ -768,6 +781,17 @@ fn (mut p Parser) parse_return_stmt() ReturnStmt {
 	}
 }
 
+fn (mut p Parser) parse_while() WhileLoop {
+	p.expect(.kw_while)
+	cond := p.parse_expr(.base)
+	if p.get_expr_type(cond) != 'bool' {
+		parse_error('While loop guard must be of type bool')
+	}
+	block := p.parse_block(false)
+
+	return WhileLoop {cond, block}
+}
+
 fn (mut p Parser) parse_if() IfStmt {
 	p.expect(.kw_if)
 	cond := p.parse_expr(.base)