Mercurial > projects > dil
view trunk/src/dil/ast/Visitor.d @ 757:e4b60543c5e8
Revised methods in class Visitor.
author | Aziz K?ksal <aziz.koeksal@gmail.com> |
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date | Wed, 13 Feb 2008 22:08:58 +0100 |
parents | c7a5499faa77 |
children | 5e3ef1b2011c |
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/++ Author: Aziz Köksal License: GPL3 +/ module dil.ast.Visitor; import dil.ast.Node; import dil.ast.Declarations, dil.ast.Expressions, dil.ast.Statements, dil.ast.Types, dil.ast.Parameters; /++ Generate visit methods. E.g.: Declaration visit(ClassDeclaration){return null;}; Expression visit(CommaExpression){return null;}; +/ char[] generateVisitMethods() { char[] text; foreach (className; classNames) text ~= "returnType!(\""~className~"\") visit("~className~" node){return node;}\n"; return text; } // pragma(msg, generateAbstractVisitMethods()); /// Gets the appropriate return type for the provided class. template returnType(char[] className) { static if (is(typeof(mixin(className)) : Declaration)) alias Declaration returnType; else static if (is(typeof(mixin(className)) : Statement)) alias Statement returnType; else static if (is(typeof(mixin(className)) : Expression)) alias Expression returnType; else static if (is(typeof(mixin(className)) : TypeNode)) alias TypeNode returnType; else alias Node returnType; } /++ Generate functions which do the second dispatch.$(BR) E.g.:$(BR) $(D_CODE Expression visitCommaExpression(Visitor visitor, CommaExpression c) { visitor.visit(c); }) The equivalent in the traditional visitor pattern would be:$(BR) $(D_CODE class CommaExpression : Expression { void accept(Visitor visitor) { visitor.visit(this); } }) +/ char[] generateDispatchFunctions() { char[] text; foreach (className; classNames) text ~= "returnType!(\""~className~"\") visit"~className~"(Visitor visitor, "~className~" c)\n" "{ return visitor.visit(c); }\n"; return text; } // pragma(msg, generateDispatchFunctions()); /++ The vtable holds a list of function pointers to the dispatch functions. +/ char[] generateVTable() { char[] text = "["; foreach (className; classNames) text ~= "cast(void*)&visit"~className~",\n"; return text[0..$-2]~"]"; // slice away last ",\n" } // pragma(msg, generateVTable()); /// The visitor pattern. abstract class Visitor { mixin(generateVisitMethods()); static mixin(generateDispatchFunctions()); /// The dispatch table. static const void*[] dispatch_vtable = mixin(generateVTable()); static assert(dispatch_vtable.length == classNames.length, "vtable length doesn't match number of classes"); // Returns the dispatch function for n. Node function(Visitor, Node) getDispatchFunction()(Node n) { return cast(Node function(Visitor, Node))dispatch_vtable[n.kind]; } Node dispatch(Node n) { // Do first dispatch. Second dispatch is done in the called function. return getDispatchFunction(n)(this, n); } final: Declaration visit(Declaration n) { return visitD(n); } Statement visit(Statement n) { return visitS(n); } Expression visit(Expression n) { return visitE(n); } TypeNode visit(TypeNode n) { return visitT(n); } Node visit(Node n) { return visitN(n); } Declaration visitD(Declaration n) { return cast(Declaration)cast(void*)dispatch(n); } Statement visitS(Statement n) { return cast(Statement)cast(void*)dispatch(n); } Expression visitE(Expression n) { return cast(Expression)cast(void*)dispatch(n); } TypeNode visitT(TypeNode n) { return cast(TypeNode)cast(void*)dispatch(n); } Node visitN(Node n) { return dispatch(n); } }