translation(直译)

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1、Chap7SemanticProcessingSyntax-directedtranslation(直譯)-analysis:variabledeclarations,typeerrors-synthesis:IR(instructionSet)oractualcodeThesemanticactionisattachedtotheproductions(orsub-treesofasyntaxtree).parsing:buildtheparsetreesemanticprocessing:buildanddecoratetheabs

2、tractsyntaxtree(AST)EX.Non-terminalsforoperatorprecedenceandassociativelyneednotbeincluded.EX.Non-terminalsusedforeaseofparsingmaybeomittedintheabstractsyntaxtree.Chap7SemanticProcessingEx.parsetree(翻譯內容以Tree呈現):=id+*<

3、factor>Constididabstractsyntaxtree(確認所使用的值):=id+*idconstidChap7SemanticProcessingSemanticroutinestraversetheAST,computingattributesofthenodesofAST.Initially,onlyleaves(i.e.terminals,e.g.const,id)haveattributes.Ex.Y:=3*X+I:=id(Y)+*id(I)const(3)id(X)Ex1.咖啡機請幫我泡2杯熱的

4、3杯冰的拿鐵咖啡機end<受詞>＜數量形容詞＞＜飲料＞＜祈使語＞＜人＞<動詞>請幫我泡＜數量形容詞＞＜數量形容詞tail＞＜數量形容詞＞＜數量形容詞tail＞＜數量＞＜形容詞＞＜數量＞＜形容詞＞λ＜咖啡＞拿鐵2杯熱的3杯冰的Ex2(includeEX1).咖啡機請幫我泡2杯熱的藍山3杯冰的拿鐵咖啡機end<受詞>＜數量形容詞＞//＜飲料＞請幫我泡＜數量形容詞＞＜數量形容詞tail＞＜數量形容詞＞＜數量形容詞tail＞＜數量＞＜形容詞＞

5、＜飲料＞λ＜咖啡＞藍山2杯熱的3杯冰的＜數量＞＜形容詞＞＜飲料＞＜咖啡＞拿鐵Chap7SemanticProcessingWethenpropagatetheattributestoothernodes,usingsomefunctions,e.g.-buildsymboltable-attachattributesofnodes-checktypes,etc.bottom-up/top-downpropagationdeclaration:=id+*idconstidexp.typesymboltable

6、checktypes:integer*orfloating*Needtoconsultsymboltablefortypesofid’s.‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘Chap7SemanticProcessingAfterattributepropagationisdone,thetreeisdecoratedandreadyforcodegeneration.WemakeanotherpassoverthedecoratedASTtogeneratecode.Actually,buildingtheASTdecora

7、tingtheASTgeneratingcodethesecanbecombinedinasinglepass.Whatwehavedescribedisessentiallytheattributegrammars(AG).Detailsinchap.14.Chap7SemanticProcessingConceptually:=id+*idconstidAttributesflowintheAST.Chap7SemanticProcessing7.1.26compilerorganizations:<1>1-passanalysis

8、andsynthesisscanningparsingcheckingtranslationinterleavedinasinglepass.Ex.Microcompilerinchap.2.Sinceco