probleme with cast from double to QString

[hbill]

hi
i have a C++ class that evaluate an arithmitic expression like 9+8-(9/5)
in the consol i have a good result.
but if i instantiate my class in a Qt project and pute the result in QLineEdit i have 0

a slot that instantate and calclate the expression :

void calculatrice::evaluateClicked()
{
    arithmeticExpression *e = new arithmeticExpression( inputeLE->text().toStdString() );
    QString st;
    st.setNum( e->evluate() );
    outputeLE->setText( st );
}

void calculatrice::evaluateClicked()
{
    arithmeticExpression *e = new arithmeticExpression( inputeLE->text().toStdString() );
    QString st;
    st.setNum( e->evluate() );
    outputeLE->setText( st );
}

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evluate() return a double

thanks
++