add for statements

examples/hello.v

@@ -63,6 +63,9 @@ fn main(a int) int {
 	str.len /= 1
 
 	awoo := [1, 2, a(), b + 2, c(31) * d]
+
+	for a in b {}
+	for idx, a in b {}
 }
 
 fn (v Typ) voidfunc() {}

src/ast.zig

@@ -158,12 +158,20 @@ pub const LoopStmt = struct {
     then_branch: Block,
 };
 
+pub const ForStmt = struct {
+    index: ?Token,
+    value: Token,
+    array: Token,
+    block: Block,
+};
+
 pub const Stmt = union(enum) {
     Expr: *Expr,
     Println: *Expr,
 
     If: IfStmt,
     Loop: LoopStmt,
+    For: ForStmt,
 
     Return: ReturnStmt,
 
@@ -212,6 +220,20 @@ pub const Stmt = union(enum) {
         return stmt;
     }
 
+    pub fn mkFor(allocator: *std.mem.Allocator, index: ?Token, value: Token, array: Token, block: Block) !*Stmt {
+        var stmt = try allocator.create(Stmt);
+        stmt.* = Stmt{
+            .For = ForStmt{
+                .index = index,
+                .value = value,
+                .array = array,
+                .block = block,
+            },
+        };
+
+        return stmt;
+    }
+
     pub fn mkReturn(allocator: *std.mem.Allocator, tok: Token, value: *Expr) !*Stmt {
         var stmt = try allocator.create(Stmt);
         stmt.* = Stmt{

src/ast_printer.zig

@@ -262,6 +262,21 @@ pub fn printStmt(ident: usize, stmt: *Stmt) void {
             std.debug.warn(")\n");
         },
 
+        .For => |forstmt| {
+            std.debug.warn("(for ");
+
+            if (forstmt.index) |index| {
+                std.debug.warn("({} {}) ", index.lexeme, forstmt.value.lexeme);
+            } else {
+                std.debug.warn("{} ", forstmt.value.lexeme);
+            }
+
+            std.debug.warn("{} ", forstmt.array.lexeme);
+
+            printBlock(ident + 1, forstmt.block, false);
+            std.debug.warn(")\n");
+        },
+
         .Return => |ret| {
             std.debug.warn("(return ");
             printExpr(ret.value);

src/parser.zig

@@ -636,6 +636,7 @@ pub const Parser = struct {
         return switch (self.peek().ttype) {
             .If => try self.parseIfStmt(),
             .Loop => try self.parseLoop(),
+            .For => try self.parseForStmt(),
             .Println => try self.parsePrintln(),
             .Return => try self.parseReturn(),
             else => try self.parseStmtExpr(),
@@ -675,6 +676,42 @@ pub const Parser = struct {
         );
     }
 
+    fn parseForStmt(self: *@This()) !*Stmt {
+        // There are two types of for in vig's V subset:
+        //  - for x in y
+        //  - for idx, x in y
+        _ = try self.consumeSingle(.For);
+
+        var index_var: ?Token = null;
+        var value_var: Token = undefined;
+
+        const subject_1 = try self.consumeSingle(.Identifier);
+
+        if (self.check(.Comma)) {
+            _ = try self.consumeSingle(.Comma);
+
+            const subject_2 = try self.consumeSingle(.Identifier);
+            index_var = subject_1;
+            value_var = subject_2;
+        } else {
+            value_var = subject_1;
+        }
+
+        _ = try self.consumeSingle(.In);
+
+        // MUST be identifier
+        var array = try self.consumeSingle(.Identifier);
+        var block = try self.parseStmtBlock();
+
+        return try Stmt.mkFor(
+            self.allocator,
+            index_var,
+            value_var,
+            array,
+            block,
+        );
+    }
+
     fn parseLoop(self: *@This()) !*Stmt {
         _ = try self.consumeSingle(.Loop);
         var expr: ?*Expr = null;