一.表达式分离算法分析

二.分离算法实现

QCalculatorDec.cpp

#include "QCalculatorDec.h"

#include <QDebug>

QCalculatorDec::QCalculatorDec()
{
    m_exp = "";
    m_result = "";

    QQueue<QString> r = split("+9.11 + ( -3 - 1 ) * -5 ");

    for(int i=0; i<r.length(); i++)
    {
        qDebug() << r[i];
    }
}

QCalculatorDec::~QCalculatorDec()
{

}

bool QCalculatorDec::isDigitOrDot(QChar c)
{
    return (('0' <= c) && (c <= '9')) || (c == '.');
}

bool QCalculatorDec::isSymbol(QChar c)
{
    return isOperator(c) || (c == '(') || (c == ')');
}

bool QCalculatorDec::isSign(QChar c)
{
    return (c == '+') || (c == '-');
}

bool QCalculatorDec::isNumber(QString s)
{
    bool ret = false;

    s.toDouble(&ret);

    return ret;
}

bool QCalculatorDec::isOperator(QString s)
{
    return (s == "+") || (s == "-") || (s == "*") || (s == "/");
}

bool QCalculatorDec::isLeft(QString s)
{
    return (s == "(");
}

bool QCalculatorDec::isRight(QString s)
{
    return (s == ")");
}

int QCalculatorDec::priority(QString s)
{
    int ret = 0;

    if( (s == "+") || (s == "-") )
    {
        ret = 1;
    }

    if( (s == "*") || (s == "/") )
    {
        ret = 2;
    }

    return ret;
}

bool QCalculatorDec::expression(const QString& exp)
{
    bool ret = false;

    return ret;
}

QString QCalculatorDec::result()
{
    return m_result;
}

QQueue<QString> QCalculatorDec::split(const QString& exp)
{
    QQueue<QString> ret;
    QString num = "";
    QString pre = "";

    for(int i=0; i<exp.length(); i++)
    {
        if( isDigitOrDot(exp[i]) )
        {
            num += exp[i];
            pre = exp[i];
        }
        else if( isSymbol(exp[i]) )
        {
            if( !num.isEmpty() )
            {
                ret.enqueue(num);

                num.clear();
            }

            if( isSign(exp[i]) && ((pre == "") || (pre == "(") || isOperator(pre)) )
            {
                num += exp[i];
            }
            else
            {
                ret.enqueue(exp[i]);
            }

            pre = exp[i];
        }
    }

    if( !num.isEmpty() )
    {
        ret.enqueue(num);
    }

    return ret;
}

输出：

"+9.11"
"+"
"("
"-3"
"-"
"1"
")"
"*"
"-5"