AST Package (3)
	n Statement u int op;     // Operator ID for statement u Label lbl;     // Label u Annotation ann;   // Embedded annotation (default: null) u code();     // Convert AST to backend intermediate        // codes (low-level bytecodes)        // As same as Expression, call-back        // ann.perform() method to metacomputation u simplify();   // Simplify statement form. For example,        // convert “a=a+1;” to “a++;” n We strongly hope to support SSA for easier program transformations.