@ disable is_zero @ expression *E; @@ E == - 0 + NULL @ disable is_zero @ expression *E; @@ - 0 + NULL == E @ disable isnt_zero @ expression *E; @@ E != - 0 + NULL @ disable isnt_zero @ expression *E; @@ - 0 + NULL != E @@ idexpression *X; statement S; @@ - if(X == NULL) + if(!X) S @@ idexpression *X; statement S; @@ - if(X != NULL) + if(X) S