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  1. 8th May 2018, 15:58 #5
    sr1s
    sr1s is offline Novice
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    Default Re: Parser for mathematic expression from QString

    I have to correct a mistake (if I had "2^(6/3)", the code returns a nan), in a second time I'll create a pow() function to have a more clear code...
    For the problem abs(-1)->abs1, or cos(0) -> cos0, a very rough solution: I change, for example, abs(-1) into math.abs{-1), and then, before processing expression, replace again "{" with "(".. Very ugly, but it's enough to avoid the transforming into math.abs-1...
    So, the code is this:
    Qt Code: 
    1. #include "math.h"
    2. #include "expression_calc.h"
    3. #include "ui_expression_calc.h"
    4. #include "QDebug"
    5. #include <QApplication>
    6. #include <QJSEngine>
    7. #include <QJSValue>
    8. #include <QObject>
    9.  
    10. Expression_calc::Expression_calc(QWidget *parent) :
    11.     QMainWindow(parent),
    12.     ui(new Ui::Expression_calc)
    13. {
    14.     ui->setupUi(this);
    15.  
    16.    }
    17.  
    18. Expression_calc::~Expression_calc()
    19. {
    20.    delete ui;
    21. }
    22.  
    23. void Expression_calc::on_CalcButton_clicked()
    24. {
    25.     QString expression= ui->exp->text();
    26.     QString exp1,exp2;
    27.  
    28.     expression.replace("pi","Math.PI");
    29.     expression.replace("abs(","Math.abs{");
    30.     expression.replace("sin(","Math.sin{");
    31.     expression.replace("cos(","Math.cos{");
    32.     expression.replace("tan","Math.tan");
    33.      //.... and so on for trigonometrical functions)
    34.  
    35.     expression.replace("sqrt","Math.sqrt");
    36.     expression.replace("(","[");
    37.     expression.replace(")","]");
    38.     expression.replace("^","POW");
    39.     expression.replace("+","PLUS");
    40.     expression.replace("-","MINUS");
    41.     expression.replace("*","MULT");
    42.     expression.replace("/","DIV");
    43.  
    44.      while (expression.contains("[")) //START SOLVING EXPRESSIONS BETWEEN BRACKETS
    45.      {
    46.  
    47.          QRegularExpression rep("\\[([^\\]]+)\\]");
    48.            QRegularExpressionMatch matchp = rep.match(expression);
    49.            QString expp_w_brackets = matchp.captured(0); //original expression with brakets
    50.            QString expp = matchp.captured(1);//expression without brakets
    51.  
    52.            while (expp.contains("POW")) //SOLVE POE EXPRESSION
    53.            {
    54.                QRegularExpression re1("(\\d+.\\d+POW)|(\\d+POW)");
    55.                QRegularExpressionMatch match1 = re1.match(expp);
    56.  
    57.                QRegularExpression re2("(POW\\d+.\\d+)|(POW\\d+)");
    58.                QRegularExpressionMatch match2 = re2.match(expp);
    59.  
    60.                if (match1.hasMatch())
    61.                {
    62.                    exp1 = match1.captured(0);
    63.                    exp1.replace("POW","");
    64.                }
    65.  
    66.                if (match2.hasMatch())
    67.                {
    68.                    exp2 = match2.captured(0);
    69.                    exp2.replace("POW","");
    70.                      }
    71.  
    72.                expp.replace (""+exp1+"" "POW"""+exp2+"" , "Math.pow(" ""+exp1+"" ","  ""+exp2+""  ")");
    73.            }
    74.  
    75.  
    76.            expp.replace ("PLUS","+");
    77.            expp.replace ("MINUS","-");
    78.            expp.replace("MULT","*");
    79.            expp.replace("DIV","/");
    80.  
    81.            QJSEngine parsexpressionp;
    82.            double resultp=parsexpressionp.evaluate(expp).toNumber();
    83.            QString BraketResult=(QString::number(resultp));
    84.            expression.replace(""+expp_w_brackets+"" ,""+BraketResult+"");
    85. }
    86.  
    87.     while (expression.contains("POW")) //SOLVE POE EXPRESSION
    88.     {
    89.         QRegularExpression re1("(\\d+.\\d+POW)|(\\d+POW)");
    90.         QRegularExpressionMatch match1 = re1.match(expression);
    91.  
    92.         QRegularExpression re2("(POW\\d+.\\d+)|(POW\\d+)");
    93.         QRegularExpressionMatch match2 = re2.match(expression);
    94.  
    95.  
    96.         if (match1.hasMatch())
    97.         {
    98.             exp1 = match1.captured(0);
    99.             exp1.replace("POW","");
    100.         }
    101.  
    102.         if (match2.hasMatch())
    103.         {
    104.             exp2 = match2.captured(0);
    105.             exp2.replace("POW","");
    106.               }
    107.  
    108.  
    109.         expression.replace (""+exp1+"" "POW"""+exp2+"" , "Math.pow(" ""+exp1+"" ","  ""+exp2+""  ")");
    110.      }
    111.  
    112.     expression.replace("{","(");
    113.     expression.replace("[","(");
    114.     expression.replace("]",")");
    115.     expression.replace ("PLUS","+");
    116.     expression.replace ("MINUS","-");
    117.     expression.replace("MULT","*");
    118.     expression.replace("DIV","/");
    119.     QJSEngine parsexpression;
    120.     double result=parsexpression.evaluate(expression).toNumber();
    121.     ui->Result->setText(QString::number(result));
    122. }
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    Last edited by sr1s; 8th May 2018 at 16:37.
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