Iingxelo kunye neengxaki ze-LeetCode ziquka ukuguqula iintlobo ze-binary. Kodwa njani ukuguqula iintlobo ze-general kwiintlobo ezahlukileyo? Indlela yokusombulula le nkqubo, kwaye iindlela ezininzi ezifumana? Makhe ufunde oku ngokufunda indlela yokuguqula i-syntax elinye kwiintlobo ezahlukileyo. Yintoni siphinde apha Yintoni iingxaki yokufunda iingxaki yokuguqula omnye kwiingxaki. Zifumaneka phantsi. 
 
 
 
 Ukuguqulwa phakathi iifomati ezahlukeneyo, ezifana ne-XML kwi-HTML. Imisebenzi ye-algorithmic, kuquka i-rotation ye-binary trees. I-Transformations ngaphakathi kwe-compilers-ayikwazi ukuqhagamshelane kwi-tree-to-tree, kodwa isib. Ukuguqulwa kwe-tree ye-syntax kwi-control flow graph. Le nqaku ebhalisiweyo kubandakanya ukuba oku kunokwenzeka. Ukusetyenziswa kwe-translation ngexesha elandelayo ngexesha elifanelekileyo kunokuba yi-transformation. Kwi-PVS-Studio, sinikeza i-coding ye-static analyzers, ngoko iinkonzo zethu zihlanganisa kunye ne-compilers ngexesha le-tooling. Kwakhona, phakathi kwimeko ezininzi, sinikeza i-Abstract Syntax Tree ( Kodwa zonke iingxelo apha ziya kubhalwe, ngoko akufuneka ulwazi oluphambili. Ukucinga   Umxholo wabanjwa ngexesha elula kakhulu: 
 
 
 
 Ufuna ukunceda iilwimi ezininzi – ngoku, sincoma kuphela i-C#, i-C/C++, kunye neJava, kodwa siphinde ukunika i-JavaScript. Thina, iqela le-Java, ufuna ukudala i-analyzer entsha kwi-Java. Ukusetyenziswa kwe-JS, kunye nokuxhomekeka kwe-TS kwizithuba, yi-TypeScript compiler. Nangona kunjalo, ibhalwe kwilwimi eyahlukileyo, ngoko kufuneka uqhagamshelane i-AST nge-gRPC. Ukusetyenzisa ukusebenza, sisebenzisa i-protobuf. Yintoni ndingathanda ngexesha le translation? 
 
 
 I-protobuf ye-representation etholakalayo ayikwazi ukuyifaka ngqo, ngenxa yokuba isakhiwo se-unchangeable, kwaye izicwangciso zithupha i-hierarchy zayo ngokupheleleyo. Ukuthatha imodeli yethu yobugcisa kubonakala ngcono. Ngokwenza oku, sincoma kuxhomekeke kwi-code-parsing frontend kwaye sincoma inkxaso kwiilwimi ezintsha. Yintoni, i was born: Ukuguqulwa i-TypeScript compiler tree, ebandayo ngu-protobuf, kwi-representation yethu. task Yintoni ndingathanda Yintoni ngokugqithisileyo siyenza? Thina siphinde (ngoku) iingxaki kunye ne-protobuf, kufuneka ukuguqulwa kwintambo eyodwa kwintlobo elinye. Zonke iintambo ze-syntax kwiilwimi efanayo, ngoko iingxaki ziquka ezincinane. Iingxaki ezininzi ziya kubhalwe ngama-isomorphically-one-to-one, kunye neengxaki ezininzi ze-cosmetic. Ngathi, iimodeli enye ingasetyenziswa iimveliso, xa ezinye usebenzisa . do...while repeat...until   Kule mzekelo, i-transformation ibonelela isakhiwo "ngoku" - siza kubhalwe nje. Kodwa kunokwenzeka izicwangciso ezininzi ezininzi. Kwi-JavaScript, umzekelo, kukho i-interpolation ye-string, eyaziwa ngokuba yi- template strings. Ngenxa yintoni, i-TypeScript ingxubevange i-expressions ngaphakathi kwe-interpolation kunye ne-text kwi-nod eyodwa, nangona kwiilwimi ezininzi, i-interpolation ifumaneka kwi-flat list.   Ukufumana i-tree kwi-right, kufuneka ukwahlula izakhiwo ze- umnxeba kwiindidi ezimbini (okanye ezincinane). Ngoko ke, ngaphandle kwe-node-to-node yokuguqulwa ngqo, siye sikuguqulwa i-property kwi-nod eyahlukileyo. TemplateSpan Ngoko ke, isebenzo oluthile uyaziwa njenge-aggregation - ukuxhaswa ama-nodes ezininzi kwi-one - kodwa umsebenzi yethu ayidinga. Kwixesha elide, yonke into kubonakala ngokucacileyo. Kodwa ukuba isakhiwo yokuqala akufanelekanga isakhiwo yedolobha? Kwi-AST isakhiwo, siya kukufuna ukuguqulwa isakhiwo ukuze kulula ukusebenza ngexesha elandelayo. Umzekelo, ukongeza njalo umzimba iinkqubo ye-pile: let a = () -> 1; // source
let a = () -> { return 1 }; // normalized
 Enter Full Screen Mode Ukukhuphela Full Screen Mode   Ngiyazi, oku kuphela umgaqo we-arbitrary enikezela ukongeza ama-nodes kwi-tree ezikhoyo ekuqaleni. Ngokutsho, siya kuba: 
 
 
 
 Ukuguqulwa kwe-node-to-node: Ukuguqulwa kwe-duplication ngqo, okungenani ukuguqulwa kwe-identifier. Ukuguqulwa kwe-property-to-node: Ukudala i-tree elements ezongezelelweyo kwi-property ye-source nodes. iinkcukacha ezivamile ze-normalization, leyo kunye neengxaki ezidlulileyo ziyafumaneka kwifoto elandelayo.   Izixhomekeke iimeko ezininzi ngamnye, kodwa i-tree ye-syntax ifumaneka kwiifayile ye-source epheleleyo. Kwixesha lokwenene, yonke into iya kuxhaswa - kwaye ngexesha elikhulu. I-declaration eyodwa kunye ne-initialization efana ubuncinane ama-nodes ezine. Just imagine how many nodes a file with thousands of lines of code will contain. let a = 2 + 5 Okwangoku, ndingathanda ukuba unayo ingcindezi into ethu siyenza. It's time to move on to practice. Indlela yokufika i-tree Ukucinga Ngaphambi kokufumana indlela yokusebenza kwezinye iintlobo, kufuneka ukufumana indlela yokuhamba iintlobo. Umqondo yokuqala ingaba ukuvelisa ingubo Ngaba ndingathanda ukuba ndingathanda ukuba ndingathanda? Ukuba le nqakraza yakho kuyinto ukuguqulwa ingubo kunye nenani elincinci yeendaba, oku kunokwenzeka ukhetho olungileyo - kodwa kungekho kwimeko yethu. I-ITERATOR iimveliso Ndicinga ngokukhawuleza iintlobo ezahlukeneyo ze-nodes kwi-diagram phezulu: kukho malunga —and that’s just three examples. Kwi-AST yethu ye-JavaScript, kukho kwimeko ezantsi iintlobo, kunye ne-source model . Wonke iintlobo ibonisa i-add-on umzekelo xa ukhangela indlela yokusebenza node. Ngoko ke, ukuba ufuna ukuyifaka ikhowudi efanelekileyo ngaphandle kwemibala, kufuneka uqhagamshelane . ten 100 even more if Iimveliso ze-Pattern Ngaba ndingathanda kwi-implementation yayo - unako ukuyifaka nge-link phezulu okanye kwiziphi na inguqulelo elinye. Kwaye, ndingathanda nje ukuba ngenxa ye-double dispatch, inani lwezimo xa usebenzise iintlobo ezahlukeneyo ze-nodes iye malunga ne-zero. Kwakhona kulula kakhulu ukuvelisa i-recursive descent. Fumana umzekelo phantsi kwe-spoiler. I-Tree Crosser Recursive interface Node {
    void accept(Visitor v);
}

interface Visitor {
    void visitBinary(Binary n);
    void visitLiteral(Literal n);
}

class Binary implements Node {
    private final Node left;
    private final Node right;

    public Binary(Node left, Node right) {
        this.left = left;
        this.right = right;
    }

    @Override public void accept(Visitor v) {
        v.visitBinary(this);
    }
}

class Literal implements Node {
    private final int value;

    public Literal(int value) {
        this.value = value;
    }

    @Override public void accept(Visitor v) {
        v.visitLiteral(this);
    }
}

class Scanner implements Visitor {
    public void scan(Node n) {
        n.accept(this); 
    }

    @Override public Binary visitBinary(Binary n) {
        scan(n.getLeft());
        scan(n.getRight());
    }

    @Override public void visitLiteral(Literal n) {

    }
}
 Enter Full Screen Mode Ukukhuphela Full Screen Mode Yintoni protobuf? Umbhali omncinci uya kufumana ukuba i-protobuf iye yandisa iimodeli yethu yokuthintela, ngoko ke yintoni i-double dispatch siza kuxhomekeke? Akukho. Akukho. I-Protobuf iye yenza nathi ukuchitha. Kodwa ekugqibeleni, sinokufumaneka ukufumana umdlali ngokwenza i-crossover esekelwe kwi-Crossover. ifayile, leyo ibonisa zonke iintlobo ze-nodes. The iindlela of such a visitor ziquka ngokwenene: .protoset visit @Override
public void visitBinaryExpression(BinaryExpression binaryExpression) {
    scan(binaryExpression.getToken());
    scan(binaryExpression.getLeft());
    scan(binaryExpression.getRight());
}
 Enter Full Screen Mode Ukukhuphela Full Screen Mode Thina ukufumana oku ngokusebenzisa   Ukusebenza: Ukucinga scan public final void scan(Object node) {
    switch (node) {
      case BinaryExpression binaryExpression ->
          visitBinaryExpression(binaryExpression);
      case UnaryExpression unaryExpression -> 
          visitUnaryExpression(unaryExpression);
      case LiteralExpression literalExpression -> 
          visitLiteralExpression(literalExpression);
      // 121 LOC more
    }
}
 Enter Full Screen Mode Ukukhuphela Full Screen Mode Ngaba kuthetha lo mfuneko elungileyo, kodwa isebenza. Ngoko ke, thina siqhagamshelane ngexesha elandelayo. 
 
 
 Umdlali wethu ngokwenene unxibelelwano. Umgangatho yokusebenza kwakhona, njengoko siphinde inokufumana umgangatho wokubhalisa logic kwiindlela yokusebenzela ngaphandle kokubhalisa if izixazululo. Ukucacisa iintlobo Okay, siqonde iingxaki zeengxaki kunye neengxaki zeengxaki. Ngoku siza kwakhona kwakhona kwi-translation. I-Node-to-Node Yenza kuqala ngexesha elula kakhulu. Ukuba siye ukwakha iintlobo, kufuneka ukugcina apho. Umgangatho elula kunokuba ukuguqulwa i-node yamanje ukusuka ngamnye umgangatho kunye nokuthumela i-parent kwi-arguments. Ukuba sincoma kwi-scanner ephantsi, ukongeza i-value ye-return ye-generic kunye ne-argument ye-generic ye-second for iindlela ezidlulileyo, sinokufumana into efanayo: visit visit interface Visitor<R, P> {
    R visitBinary(Binary n, P parent);
    R visitLiteral(Literal n, P parent);
}

class Builder extends Scanner<JsNode, JsNode> {
    @Override
    public JsNode visitBinary(Binary n, JsNode parent) {
        var left = (JsExpression) scan(n.getLeft());
        var right = (JsExpression) scan(n.getRight());
        return new JsBinary(left, right);
    }

    @Override 
    public JsNode visitLiteral(Literal n, JsNode parent) {
        return new JsLiteral(n.getValue());
    }
}
 Enter Full Screen Mode Ukukhuphela Full Screen Mode Kule nendlela elula kakhulu, sinokufumana i-structure ye-tree. Ukuze ukunceda ukuxhaswa, ndiyifake i-nodes ye-tree ye-target ne-prefix ekuqaleni kweqela leqela. Js Ubungqina-to-node Le ngxaki ayinayo kakhulu, kodwa apha siza kufuneka i-parent elidlulileyo. Ngaphandle kokuphathelisa ngqo, sinikezela i-logic. Thina siye kwakhona isibonelo se-interpolation: @Override
public JsNode visitTemplateSpan(TemplateSpan templateSpan, JsNode parent) {
    var interpolation = (Interpolation) parent;
    var expr = new InterpolationExpression();
    interpolation.add(expr);
    interpolation.setExpression(
        scan(templateSpan.getExpression())
    );

    // tail is optional
    if (templateSpan.hasTemplateTail()) {
        interpolation.add(new InterpolationText(
            templateSpan.getTemplateTail().getValue()
        ));
    }

    return null;
}
 Enter Full Screen Mode Ukukhuphela Full Screen Mode Ukusuka kweSkype Ukusuka —ukuba sinikezela abantwana nge-parent eyahlukileyo njenge-argument. TemplateSpan null Ukucaciswa Ndiyathanda iimpawu zayo ngexesha elidlulileyo ngexesha elidlulileyo ngexesha elidlulileyo - zonke iimeko apha ezizodwa. Kwiimeko sikhuluza, kwaye ukuguqulwa kunyuka ngokushesha. Kwiimeko ezininzi, iingxaki. Ngokubanzi, sisetyenziswa umthetho elandelayo: ukuguqulwa ukuba ukuguqulwa kwe-control flow okanye I-complicated. Yintoni ebonakalayo njengoko "okungabonakali kakhulu" ibekwe kwinxalenye ye-developer kunye ne-manager yayo :) avoid too Izixhobo ze-pile iye zithunyelwe njengesibonelo ezidlulileyo ziquka ngokuphathelene, nangona kukho iinkcukacha ezininzi ezidlulileyo. Yintoni I-methode yobungakanani kubonakala ngexesha elandelayo: visit @Override
public JsNode visitArrowFunction(
    ArrowFunction arrowFunction,
    JsNode parent
) {
    var func = new JsArrowFunction();
    // link inside
    scan(arrowFunction.getParameterDeclarationList(), func);

    // OK
    if (arrowFunction.hasBlock()) {
        func.setBlock(
            scan(arrowFunction.getBlock())
        );
    } else if (arrowFunction.hasExpression()) {
        var normalized = normalizeArrow(
            arrowFunction
        );
        func.setBlock(normalized);
    }

    return func;
}
 Enter Full Screen Mode Ukukhuphela Full Screen Mode I-Transformation ifumaneka kwi : normalizeArrow public JsBlock normalizeArrow(ArrowFunction f) {
    var block = new JsCodeBlock();
    block.setFlag(Flag.SYNTHETIC);

    var ret = new JsReturn();
    ret.setFlag(Flag.SYNTHETIC);
    block.addStatement(ret);

    var expr = scan(f.getExpression());
    ret.setExpression(expr);

    return block;
}
 Enter Full Screen Mode Ukukhuphela Full Screen Mode Ukongezelela ekwenzeni ama-nodes, siye sinikezela njenge-synthetic, njengoko ayikho kwi-tree yokuqala-ukuthathelela ngempumelelo njenge- "virtual". Yinto efanelekileyo kwi-analytics ye-static - ngenxa ye-heuristics kwiimeko ze-diagnostic, sinokufundisa ukuba umdlali wabhala izinto efana ne-heuristics. —i-it is just an artifact of our transformations. Okay, oku yonke ngenxa ye-transformations. (var) -> { return console.log(var) } I-elephant kwi-room Kule ngexesha, sisibandakanya zonke iingcango ezisemgangatho ezihambelana nokuphendula umsebenzi. 
 
 
 
 
 Thola ngokugqithisileyo, ukhuseleko kwimeko yemveliso yamanje nge-parameters kunye ne-return values ye-visit methods. Kukho iintlobo ezimbini ezaziwayo: node-to-node kunye ne-property-to-node. Yintoni i-transformation ye-athypical: i-tree normalization. Ngenxa yobugcisa, sinokufumana ingubo elifanayo - kodwa entsha, ezahlukileyo. Yintoni iingxaki ezininzi ziyafumaneka isisombululo. Nceda ushiye: i-target tree   , yaye ingxubevange . Le ingxaki kubaluleke kakhulu kwiintlobo protobuf. Oku kubalulekile ukuba   iimveliso Ukucinga Qhagamshelana nathi ngexesha elifanelekileyo? 100 node types 263 types hand-write visit scan hundreds or thousands of times   Ukusabela inkinga kwakhona kubonakala kwi-text. Njengoko i-crossover yokuqala ingasetyenziswa ekuqaleni iifayile, ngoko iintlawulo eziqhelekileyo yokudlulisa kungenziwa yi-code-generated ngokuxhomekeke kwinkqubo ye-configuration. Kodwa siza kuxhomekeke oku - kwaye indlela yokufaka kwi-normalization ebonakalayo - ixesha elinye. .protoset Ukucinga Yintoni iingxaki ndingathanda kwimveliso yam. Nangona ndifumana kuphela indawo, ndiye ndingathanda iingxaki ezininzi ezibalulekileyo: iintlobo eziqhelekileyo, ukhetho phakathi kwe-iterator kunye ne-visitor, ukuveliswa kwe-visitor non-trivial. Thina kwakhona ndingathanda nge-lens ye-analysis ye-synthetic nodes kunye nenkqubo ye-normalization. Nangona kunjalo, ndingathanda ukuba ufunde into olutsha malunga nenkqubo yokusebenza kunye neentambo. Ungafuneka iinkcukacha malunga ne-theme yokusebenza kunye ne-analyzers ezintsha ngokubanzi - ukubhalisela kwi-PVS-Studio kwaye article yethu ngenyanga I-You are welcome to try the tool for free . Ukucinga Ukucinga Yiba Ukuba ufuna ukuyifaka iingxelo zayo, ubhalisele kwi-my personal . Ukucinga

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