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expression.cpp
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expression.cpp
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#include "expression.h"
#include <QDebug>
Expression::Expression() {
}
const Expression* Expression::parse(const QString expression) {
Tokenizer parser(expression);
Exception* error = nullptr;
QList<const Token*>* tokens = parser.tokenize(&error);
if (error) {
return new Expression(error);
}
qDebug() << parser.toString();
QStack<const Token*> operators;
QStack<const Expression*> operands;
for (const Token* token : *tokens) {
switch (token->type) {
case OPERATOR: {
if (token->content == ")") {
bool hasLeftBracket = false;
while (!operators.empty()) {
const Token* op = operators.pop();
if (op->content == "(") {
hasLeftBracket = true;
break;
}
const Expression *rhs = operands.empty() ? nullptr : operands.pop(),
*lhs = operands.empty() ? nullptr : operands.pop();
if (!rhs || !lhs) {
const CompoundExpression* expr = new CompoundExpression(
new SyntaxError(QString("Missing operands for operator ").arg(op->content)));
return expr;
}
operands.push(new CompoundExpression(op->content, lhs, rhs));
}
if (!hasLeftBracket) {
const CompoundExpression* expr = new CompoundExpression(new SyntaxError("Missing \"(\""));
return expr;
}
break;
} else if (token->content == "(") {
operators.push(token);
} else {
while (!operators.empty() && operators.top()->precedence >= token->precedence) {
const Expression *rhs = operands.empty() ? nullptr : operands.pop(),
*lhs = operands.empty() ? nullptr : operands.pop();
if (!rhs || !lhs) {
const CompoundExpression* expr = new CompoundExpression(
new SyntaxError(QString("Missing operands for operator ").arg(token->content)));
return expr;
}
operands.push(new CompoundExpression(operators.pop()->content, lhs, rhs));
}
operators.push(token);
}
break;
}
case CONSTANT:
operands.push(new ConstantExpression(token));
break;
case IDENTIFIER:
operands.push(new IdentifierExpression(token));
break;
default:
break;
}
}
while (!operators.empty()) {
const Token* op = operators.pop();
const Expression *rhs = operands.empty() ? nullptr : operands.pop(),
*lhs = operands.empty() ? nullptr : operands.pop();
if (!rhs || !lhs) {
if (op->content == "(") {
const CompoundExpression* expr = new CompoundExpression(new SyntaxError("Missing \")\""));
return expr;
}
const CompoundExpression* expr =
new CompoundExpression(new SyntaxError(QString("Missing operands for operator ").arg(op->content)));
return expr;
}
operands.push(new CompoundExpression(op->content, lhs, rhs));
}
if (operands.empty()) {
const Expression* expr = new Expression(new SyntaxError("Missing expression"));
return expr;
}
return operands.pop();
}
const Value* Expression::evaluate(Runtime*) const {
return nullptr;
}
QString Expression::ast() const {
return "";
}
QString Expression::getIdentifierName() const {
return "";
}
QString Expression::toString() const {
return "";
}
ExpressionType Expression::getType() const {
return UNKOWN_EXP;
}
Expression::~Expression() {
}
// ConstantExpression
ConstantExpression::ConstantExpression(const Token* token) {
QChar prefix = token->content[0];
if (prefix == '"' || prefix == '\'') {
value = new StringValue(token->content.section(prefix, 1, 1));
} else {
value = new IntegerValue(token->content.toInt());
}
}
const Value* ConstantExpression::evaluate(Runtime*) const {
return value;
}
QString ConstantExpression::ast() const {
return value->ast();
}
QString ConstantExpression::toString() const {
return QString("ConstantExpression(%1)").arg(value->ast());
}
ExpressionType ConstantExpression::getType() const {
return CONST_EXP;
}
ConstantExpression::~ConstantExpression() {
delete value;
}
// IdentifierExpression
IdentifierExpression::IdentifierExpression(const QString i): identifier(i) {
}
IdentifierExpression::IdentifierExpression(const Token* token): identifier(token->content) {
}
const Value* IdentifierExpression::evaluate(Runtime* context) const {
return context->symbols->getValue(identifier);
}
QString IdentifierExpression::getIdentifierName() const {
return identifier;
}
QString IdentifierExpression::ast() const {
return identifier;
}
QString IdentifierExpression::toString() const {
return QString("IdentifierExpression(%1)").arg(identifier);
}
ExpressionType IdentifierExpression::getType() const {
return IDENTIFIER_EXP;
}
// CompoundExpression
CompoundExpression::CompoundExpression(const QString o, const Expression* l, const Expression* r)
: op(o), lhs(l), rhs(r) {
}
const Value* CompoundExpression::evaluate(Runtime* context) const {
const Value& right = *rhs->evaluate(context);
if (op == "=") {
context->symbols->setValue(lhs->getIdentifierName(), &right);
return &right;
}
const Value& left = *lhs->evaluate(context);
if (op == "+") {
return left + right;
}
if (op == "-") {
return left - right;
}
if (op == "*") {
return left * right;
}
if (op == "**") {
return left.pow(right);
}
if (op == "/") {
return left / right;
}
throw new SyntaxError("Illegal operator in expression");
return 0;
}
QString CompoundExpression::ast() const {
return op + indent(QString("\n%1\n%2").arg(lhs->ast()).arg(rhs->ast()));
}
QString CompoundExpression::toString() const {
return QString("CompoundExpression(%1, %2, %3)").arg(op).arg(lhs->toString()).arg(rhs->toString());
}
ExpressionType CompoundExpression::getType() const {
return COMPOUND_EXP;
}
QString CompoundExpression::getOp() const {
return op;
}
CompoundExpression::~CompoundExpression() {
delete lhs;
delete rhs;
}