ast: add printing of Variable Expr

- ast: simplify stmt printing from printNode
 - parser: create variables on parsePrimary

examples/hello.v

@@ -9,5 +9,5 @@ fn main(a int) int {
 	1 + 2 + 3 + 4
 	1 + 1 * 1
 	3 / (51 + 2)
-	println(2 * 1956)
+	println(2 * 1956 + a)
 }

src/ast.zig

@@ -58,18 +58,31 @@ pub const Expr = union(enum) {
     Binary: BinaryExpr,
     Unary: UnaryExpr,
     Literal: LiteralExpr,
+    Variable: Token,
     Grouping: *Expr,
 };
 
+pub const VarDecl = struct {
+    name: Token,
+    initializer: *Expr,
+};
+
 pub const Stmt = union(enum) {
     Expr: *Expr,
     Println: *Expr,
+    VarDecl: VarDecl,
 
     pub fn mkPrintln(allocator: *std.mem.Allocator, expr: *Expr) !*Stmt {
         var println = try allocator.create(Stmt);
         println.* = Stmt{ .Println = expr };
         return println;
     }
+
+    pub fn mkVarDecl(allocator: *std.mem.Allocator, name: Token, init: *Expr) !*Stmt {
+        var vardecl = try allocator.create(Stmt);
+        vardecl.* = Stmt{ .VarDecl = VarDecl{ .name = name, .initializer = init } };
+        return vardecl;
+    }
 };
 
 pub const Node = union(NodeType) {
@@ -149,22 +162,11 @@ pub fn printNode(node: *Node, ident: usize) void {
         },
 
         .Stmt => |stmt| blk: {
-            switch (stmt.*) {
-                .Println => |expr| blk2: {
             printIdent(ident);
-                    std.debug.warn("println(");
-                    printExpr(expr);
+            printStmt(stmt);
             std.debug.warn("\n");
         },
 
-                .Expr => |expr| {
-                    printIdent(ident);
-                    printExpr(expr);
-                    std.debug.warn("\n");
-                },
-            }
-        },
-
         else => {
             print(ident, "unknown node: {}\n", node);
         },
@@ -197,7 +199,9 @@ pub fn printExpr(expr: *Expr) void {
             }
         },
 
-        else => std.debug.warn("unknown"),
+        .Variable => |token| std.debug.warn("{}", token.lexeme),
+
+        else => std.debug.warn("UnknownExpr-{}", @tagName(expr.*)),
     }
 }
 
@@ -205,5 +209,7 @@ pub fn printStmt(stmt: *Stmt) void {
     switch (stmt.*) {
         .Println => |expr| parenthetize("println", &[_]*Expr{expr}),
         .Expr => |expr| printExpr(expr),
+
+        else => std.debug.warn("STMT_UNKNOWN"),
     }
 }

src/parser.zig

@@ -240,6 +240,13 @@ pub const Parser = struct {
         return expr;
     }
 
+    fn mkVariable(self: *Parser, variable: Token) !*ast.Expr {
+        var expr = try self.allocator.create(Expr);
+        expr.* = Expr{ .Variable = variable };
+
+        return expr;
+    }
+
     pub fn parse(self: *Parser) !*ast.Node {
         self.tokens = try self.allocator.alloc(Token, 0);
         var root = try ast.mkRoot(self.allocator);
@@ -511,6 +518,7 @@ pub const Parser = struct {
             .Integer => try self.mkInteger(lexeme),
             .Float => try self.mkFloat(lexeme),
             .String => try self.mkString(lexeme),
+            .Identifier => try self.mkVariable(self.peek()),
 
             .LeftParen => blk: {
                 _ = try self.nextToken();