Deklarierte Namen in MicroJava

Transkript

1 Deklarierte Namen in MicroJava Programm Konstanten Globale iablen Klassen Felder oden Formale Parameter Lokale iablen Program() ConstDecl() Decl() level = ClassDecl() Decl() level = oddecl() FormPars() Decl() level = Wird ein Name deklariert, wird er in die Symbolliste eingefügt

2 Objektknoten class Obj { enum Kind { Con,,,, Prog Kind kind; String name; Struct type; int val; // Con: value int adr; //, : address int level; // : = global, = local int npars; // : number of parameters // : parameters and local objects // Prog: global variables, constants, // classes and methods Map<String, Obj> locals; 2

3 Strukturknoten und ScopeKnoten class Struct { enum Kind { None, Int, Char,, Class Kind kind; Struct elem; // : element type Map<String, Obj> fields; // Class: list of fields int nrfields() { return fields.size(); // Class class Scope { Scope outer; // next outer scope Map<String, Obj> locals; // list of objects in this scope int ns; // number of variables in this scope 3

4 Symboltabelle class Tab { public static final Struct,,, null; public Obj noobj, chrobj, ordobj, lenobj; public Parser parser; // target for errors public Scope curscope; // current scope private int level; // nesting level of current scope public Tab(Parser parser); public void openscope(); public void closescope(); public Obj insert(obj.kind kind, String name, Struct type); public Obj find(string name); public Obj findfield(string name, Struct type); 4

5 Füllen der Symbolliste /** Decl = ident { "," ident ";". */ private void Decl() { (); Struct type = (); check(ident); tab.insert(obj.kind., t.str, type); while (sym == comma) { scan(); check(ident); tab.insert(obj.kind., t.str, type); check(semicolon); 5

6 Symbolliste verwenden /** = ident [ "[" "]" ]. */ private void Struct () { { check(ident); Obj o = tab.find(t.str); if (o.kind!= Obj.Kind.) { error(no_type); Struct type = o.type; if (sym == lbrack) { scan(); check(rbrack); type = new Struct(type); return type; 6

7 Klassen /** ClassDecl = "class" ident "{" {Decl "". */ private void ClassDecl() { check(class_); check(ident); Obj clazz = tab.insert(obj.kind., t.str, new Struct(Struct.Kind.Class)); check(lbrace); tab.openscope(); while (sym == ident) { Decl(); check(rbrace); clazz.type.fields = tab.curscope.locals; tab.closescope(); 7

8 Beispiel: Symbollistenaufbau program ABC char[] c; int max; char npp; { int put (int x) { x++; print(x, 5); npp = 'C'; return x; 8

9 9 Beispiel: Bei Punkt Vordefinierte n und Objekte: Struktur der 3 Knotenarten: Int Char kind name type next val / adr level npars locals Obj kind elem n fields Struct outer locals ns Scope Class null None "noobj" noobj Con "null" null Prog "ABC" "chr" "ord" "len" scope "Universe" "i" "ch" "arr" topscope "int" "char"

10 Beispiel: Bei Punkt topscope 2 3 "c" "max" "npp" 2 "put" scope "ABC" Con "null" null Prog "ABC" "chr" "ord" "len" scope "Universe" "i" "ch" "arr" "int" "char"

11 Beispiel: Bei Punkt topscope "x" scope "put" 3 "c" "max" "npp" 2 "put" scope "ABC" Con "null" null Prog "ABC" "chr" "ord" "len" scope "Universe" "i" "ch" "arr" "int" "char"

12 2 Beispiel: Bei Punkt "x" 3 topscope "c" "max" "npp" 2 "put" scope "ABC" Con "null" null Prog "ABC" "chr" "ord" "len" scope "Universe" "i" "ch" "arr" "int" "char"

13 3 Beispiel: Bei Punkt topscope "x" "c" "max" "npp" 2 "put" scope "ABC" Con "null" null Prog "ABC" "chr" "ord" "len" scope "Universe" "i" "ch" "arr" "int" "char"