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struct Token { // In globalem Vektor, Zugriff über globale Variable.
int type; // Definiere Konstanten.
double value;
Token(int type) : type(type) {}
Token(int type, int value) : type(type), value(value) {}
};
struct Expression { // Die folgenden Klassen nur für den AST.
virtual ~Expression() {};
virtual double getValue() = 0;
};
struct Atom : public Expression {
double value;
Atom(int value) : value(value) {};
double getValue() { return value; }
};
struct BinaryExpression : public Expression {
Expression *lhs, *rhs;
BinaryExpression(Expression *lhs, Expression *rhs) : lhs(lhs), rhs(rhs) {}
~BinaryExpression() { delete lhs; delete rhs; }
};
struct Addition : public BinaryExpression {
Addition(Expression *lhs, Expression *rhs) : BinaryExpression(lhs, rhs) {}
double getValue() { return lhs->getValue() + rhs->getValue(); }
};
Expression* parseF() {
Expression *lhs;
switch(tokens[token].type) {
case NUMBER: return new Atom(tokens[token++].value);
case LEFT_PAR:
token++;
lhs = parseA();
token++;
return lhs;
default:
return NULL;
}}
Expression* parseA_(Expression *lhs) {
Expression *plus, *minus;
if (token >= (int)tokens.size()) return lhs;
switch(tokens[token].type) {
case ADDITION:
token++;
plus = new Addition(lhs, parseS());
return parseA_(plus);
case SUBTRACTION:
token++;
minus = new Subtraction(lhs, parseS());
return parseA_(minus);
default:
return lhs;
}}
Expression* parseA() {
Expression *lhs = parseS(); return parseA_(lhs);
}
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