1 files changed, 19 insertions, 0 deletions
diff --git a/src/parse.zig b/src/parse.zig
index 24d6e42..7daa3f8 100644
--- a/src/parse.zig
+++ b/src/parse.zig
@@ -24,9 +24,28 @@ pub const Expr = struct {
             const Op = enum {
                 plus,
                 minus,
+
+                pub fn format(self: Op, comptime fmt: []const u8, options: std.fmt.FormatOptions, writer: anytype) !void {
+                    _ = fmt;
+                    _ = options;
+                    try writer.writeByte(switch (self) {
+                        .plus => '+',
+                        .minus => '-',
+                    });
+                }
             };
         };
     };
+
+    pub fn format(self: Expr, comptime fmt: []const u8, options: std.fmt.FormatOptions, writer: anytype) !void {
+        _ = fmt;
+        _ = options;
+        switch (self.type) {
+            .integer_literal => try writer.print("<int>", .{}),
+            .bin_op => |bin_op| try writer.print("({} {} {})", .{ bin_op.lhs, bin_op.op, bin_op.rhs }),
+            .invalid => try writer.print("<invalid>", .{}),
+        }
+    }
 };
 
 pub fn expression(allocator: Allocator, lexer: *Peekable(Lexer)) error{OutOfMemory}!*Expr {