 the expression contains implicit arguments and the list of Var  * arguments contains a placeholder ("_"). */ inline Func lambda(const Var &x, const Var &y, const Var &z, const Expr &e) {     Func f("lambda" + Internal::unique_name('_'));     f(x, y, z) = e;     return f; }  /** Create a 0-D halide function in the first f