Public void visitwhilenode p cse341 programming cse341

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Unformatted text preview: Fall 2011 staVc type of w.cond (ExpNd). •  Typically an error (usually no “visit(ExpNd e)”). Winter 2013 dynamic type of w.cond (e.g., LessThan). •  Accept staVcally selects correct visit method. UW CSE 401 (Michael Ringenburg) 4 How do we traverse AST? public void visit(WhileNode p) {
 CSE341: Programming CSE341: Programming Languages Languages p.expr.accept(this);! p.stmt.accept(this);! Lecture …! Lecture 1 1 }!ourse Mechanics Mechanics Course C ML Variable Bindings M o Variable Bindings •  Visitors L Pen control the traversal –  The visitor knows what kDan of traversal it needs – may ind Grossman Dan Grossman be different for different operaVons/nodes. Fall 2011 Fall opVmizaVon eliminates code that will –  E.g., imagine an 2011 never execute (this is called “Dead Code EliminaVon”). •  No need to traverse porVons of the tree that you’ve proved won’t execute. –  Or, imagine a pass that records all variable declaraVons •  No need traverse parts of the AST where declaraVons can’t occur. Winter 2013 UW CSE 401 (Michael Ringenburg) 5 What Do Visitors Do? CSE341: Programming •  A CSE341: Programming Languages Languages visitor funcVon has a reference to the node it is visiVng (the parameter)...
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