statement to expression

example.cs

        void example() {
            var b = Expr<bool>(() => {
                switch (1) {
                    case 1: return true;
                    default: return false;
                }
            });
        }

progn.cs

        public static TReturn Expr<TReturn>(Func<TReturn> body) {
            return body();
        }

        public static TReturn Progn<TReturn>(Func<TReturn> body) {
            return body();
        }