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calc.cpp
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calc.cpp
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#include "calc.h"
Calc::Calc(QString ss)
{
string str = ss.toStdString();
expression = new char[str.length() + 1];
strcpy(expression, str.c_str());
lastToken = OPAREN;
}
//enum token {OPAERN, ADD, SUB, MUL, DIV, MOD, POW, CPAREN, VALUE, EOL};
Exp* Calc::makeSyntaxTree()
{
token lastOp, topOp;
Exp* currentValue;
vector<token> op;
vector<Exp*> node;
char* str = expression;
while((lastOp = getOp(currentValue)) != EOL) {
lastToken = lastOp;
switch(lastOp) {
case VALUE:
node.push_back(currentValue);
break;
case OPAREN:
case POW:
op.push_back(lastOp);
break;
case CPAREN:
while(!op.empty() && (topOp = op.back()) != OPAREN) {
op.pop_back();
connectSyntaxNode(topOp, node);
}
if(topOp != OPAREN) {
throw QString("非法表达式(缺括号)");
} else {
op.pop_back();
}
break;
case MUL:
case DIV:
case MOD:
while(!op.empty() && (topOp = op.back()) >= MUL) {
op.pop_back();
connectSyntaxNode(topOp, node);
}
op.push_back(lastOp);
break;
case ADD:
case SUB:
while(!op.empty() && (topOp = op.back()) >= MUL) {
op.pop_back();
connectSyntaxNode(topOp, node);
}
op.push_back(lastOp);
break;
default:
break;
}
}
while(!op.empty()) {
connectSyntaxNode(op.back(), node);
op.pop_back();
}
expression = str;
if(node.empty() || node.size() > 1) {
throw QString("非法表达式");
return nullptr;
}
return node.back();
}
//enum token {OPAREN, ADD, SUB, MUL, DIV, MOD, POW, CPAREN, VALUE, EOL};
Calc::token Calc::getOp(Exp*& value)
{
while(*expression && *expression == ' ')
++expression;
if(*expression == '\0') return EOL;
if(isLetter(*expression)) {
QString s = "";
while(isLetter(*expression) || isNum(*expression)) {
s += (*expression);
++expression;
}
if(s == "MOD") {
return MOD;
}
value = new VarExp(s);
return VALUE;
}
if(isNum(*expression)) {
int val = 0;
while(isNum(*expression)) {
val = val * 10 + *expression - '0';
++expression;
}
value = new ConstExp(val);
return VALUE;
}
switch (*expression) {
case '(':
++expression;
return OPAREN;
case ')':
++expression;
return CPAREN;
case '+':
++expression;
return ADD;
case '-':
if(lastToken != VALUE || lastToken != CPAREN) {
++expression;
while(*expression && *expression == ' ')
++expression;
if(isNum(*expression)) {
int val = 0;
while(isNum(*expression)) {
val = val * 10 + *expression - '0';
++expression;
}
value = new ConstExp(-val);
return VALUE;
}
} else {
++expression;
return SUB;
}
break;
case '/':
++expression;
return DIV;
case '*':
++expression;
if(*expression && *expression == '*') {
++expression;
return POW;
} else {
return MUL;
}
}
throw QString("非法表达式");
}
bool Calc::stringIsNum(QString s)
{
QRegExp regExp("[0-9]+");
if(regExp.exactMatch(s)) {
return true;
}
return false;
}
bool Calc::isLetter(char c)
{
if((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')) {
return true;
}
return false;
}
bool Calc::isNum(char c)
{
if(c >= '0' && c <= '9') {
return true;
}
return false;
}
//enum token {OPAERN, ADD, SUB, MUL, DIV, MOD, POW, CPAREN, VALUE, EOL};
void Calc::connectSyntaxNode(token t, vector<Exp*>& node)
{
QString s = "";
Exp* pLeft, * pRight;
if(node.empty()) {
throw QString("非法表达式");
} else pRight = node.back();
node.pop_back();
if(node.empty()) {
throw QString("非法表达式");
} else pLeft = node.back();
node.pop_back();
IdentifierExp* res = new IdentifierExp("", 0, pLeft, pRight);
switch(t) {
case ADD:
res->name = "+";
break;
case SUB:
res->name = "-";
break;
case MUL:
res->name = "*";
break;
case DIV:
res->name = "/";
break;
case MOD:
res->name = "MOD";
break;
case POW:
res->name = "**";
break;
default:
break;
}
node.push_back(res);
}