143 lines
3.7 KiB
Java
143 lines
3.7 KiB
Java
package ssw.mj.impl;
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import ssw.mj.Errors;
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import ssw.mj.symtab.Obj;
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import ssw.mj.symtab.Scope;
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import ssw.mj.symtab.Struct;
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public final class Tab {
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// Universe
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public static final Struct noType = new Struct(Struct.Kind.None);
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public static final Struct intType = new Struct(Struct.Kind.Int);
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public static final Struct charType = new Struct(Struct.Kind.Char);
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public static final Struct nullType = new Struct(Struct.Kind.Class);
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public final Obj noObj, chrObj;
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public Obj ordObj, lenObj;
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/**
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* Only used for reporting errors.
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*/
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private final Parser parser;
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/**
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* The current top scope.
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*/
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public Scope curScope = null;
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// First scope opening (universe) will increase this to -1
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/**
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* Nesting level of current scope.
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*/
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private int curLevel = -2;
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public Tab(Parser p) {
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parser = p;
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// setting up "universe" (= predefined names)
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// opening scope (curLevel goes to -1, which is the universe level)
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openScope();
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noObj = new Obj(Obj.Kind.Var, "noObj", noType);
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insert(Obj.Kind.Type, "int", intType);
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insert(Obj.Kind.Type, "char", charType);
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insert(Obj.Kind.Con, "null", nullType);
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chrObj = insert(Obj.Kind.Meth, "chr", charType);
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openScope();
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Obj iVarObj = insert(Obj.Kind.Var, "i", intType);
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iVarObj.level = 1;
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chrObj.nPars = curScope.nVars();
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chrObj.locals = curScope.locals();
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closeScope();
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// TODO Exercise UE-P-4: build "ord" universe method and store in ordObj
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ordObj = insert(Obj.Kind.Meth, "ord", intType);
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openScope();
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Obj chVarObj = insert(Obj.Kind.Var, "ch", charType);
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chVarObj.level = 1;
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ordObj.nPars = curScope.nVars();
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ordObj.locals = curScope.locals();
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closeScope();
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// TODO Exercise UE-P-4: build "len" universe method and store in lenObj
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final var notypeArrStruct = new Struct(noType);
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lenObj = insert(Obj.Kind.Meth, "len", intType);
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openScope();
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Obj arrVarObj = insert(Obj.Kind.Var, "arr", notypeArrStruct);
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arrVarObj.level = 1;
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lenObj.nPars = curScope.nVars();
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lenObj.locals = curScope.locals();
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closeScope();
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// still on level -1
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// now that the universe is constructed, the next node that will be added is the Program itself
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// (which will open its own scope with level 0)
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}
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// ===============================================
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// TODO Exercise UE-P-4: implementation of symbol table
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// ===============================================
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public void openScope() {
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curScope = new Scope(curScope);
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curLevel++;
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}
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public void closeScope() {
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curScope = curScope.outer();
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curLevel--;
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}
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public Obj insert(Obj.Kind kind, String name, Struct type) {
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final var obj = new Obj(kind, name, type);
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if (kind == Obj.Kind.Var) {
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obj.adr = curScope.nVars();
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obj.level = curLevel;
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}
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final var duplicate = curScope.locals().get(name);
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if (duplicate != null) {
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parser.error(Errors.Message.DUPLICATE_NAME_IN_SCOPE, name);
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}
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curScope.insert(obj);
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// TODO Exercise UE-P-4
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return obj;
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}
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/**
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* Retrieves the object with <code>name</code> from the innermost scope.
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*/
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public Obj find(String name) {
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// TODO Exercise UE-P-4
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var scope = curScope;
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while (scope != null) {
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final var result = scope.locals().get(name);
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if (result != null) return result;
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scope = scope.outer();
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}
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return noObj;
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}
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/**
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* Retrieves the field <code>name</code> from the fields of
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* <code>type</code>.
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*/
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public Obj findField(String name, Struct type) {
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// TODO Exercise UE-P-5
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final var fieldObject = type.findField(name);
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return fieldObject == null ? noObj : fieldObject;
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}
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// ===============================================
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// ===============================================
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}
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