can some one help me the math in my code dose not work when i press the equal button it just clears the operation and anything that follows i cant sema to fix it$.$void CalFrame::OnButtonClicked$($wxCommandEvent& event$)$

$\{$

int buttonId $=$ event.GetId$()$;

wxString buttonText;

if $($buttonId $>=$ ID$\_$BUTTON$\_0$ && buttonId $<=$ ID$\_$BUTTON$\_9)\{$

buttonText $=$ wxString::Format$("\%$c$",$ buttonId $-$ ID$\_$BUTTON$\_0+\text{'}0\text{'})$;

$\}$

else $\{$

switch $($buttonId$)\{$

case ID$\_$BUTTON$\_$PLUS:

buttonText $="+"$;

break;

case ID$\_$BUTTON$\_$MINUS:

buttonText $="-"$;

break;

case ID$\_$BUTTON$\_$MULTIPLY:

buttonText $="*"$;

break;

case ID$\_$BUTTON$\_$DIVIDE:

buttonText $="/"$;

break;

case ID$\_$BUTTON$\_$MOD:

buttonText $="\%"$;

break;

case ID$\_$BUTTON$\_$DECIMAL:

buttonText $="."$;

break;

case ID$\_$BUTTON$\_$CLEAR:

OnClearButtonClick$($event$)$;

return;

break;

case ID$\_$BUTTON$\_$EQUAL:

buttonText $="="$;

OnCalculate$($event$)$;

return;

break;

case ID$\_$BUTTON$\_$TAN:

buttonText $=$ "TAN";

break;

case ID$\_$BUTTON$\_$SIN:

buttonText $=$ "SIN";

break;

case ID$\_$BUTTON$\_$CON:

buttonText $=$ "CON";

break;

case ID$\_$BUTTON$\_$NEGATIVE:

buttonText $="(-)"$;

break;

case ID$\_$BUTTON$\_$BACKSPACE:

OnBackspace$($event$)$;

return;

break;

$\}$

$\}$

textControl$->$AppendText$($buttonText$)$;

$\}$

void CalFrame::OnClearButtonClick$($wxCommandEvent& event$)$

$\{$

textControl$->$Clear$()$;

$\}$

void CalFrame::OnCalculate$($wxCommandEvent& event$)$

$\{$

wxString expression $=$ textControl$->$GetValue$()$;

double result;

if $($EvaluateExpression$($expression$,$ result$))\{$

textControl$->$SetValue$($wxString::Format$("\%$g$",$ result$))$;

$\}$

else $\{$

textControl$->$SetValue$("$Error$")$;

$\}$

$\}$

void CalFrame::OnBackspace$($wxCommandEvent& event$)$

$\{$

wxString currentValue $=$ textControl$->$GetValue$()$;

if $(!$currentValue.empty$())\{$

currentValue.RemoveLast$()$;

textControl$->$SetValue$($currentValue$)$;

$\}$

$\}$

bool CalFrame::EvaluateExpression$($const wxString & expression, double& result$)$

$\{$

if $($expression$.$empty$())$

return false;

std::istringstream iss$($expression$.$ToStdString$())$;

std::vector tokens;

std::string token;

while $($iss $>>$ token$)\{$

tokens.push$\_$back$($token$)$;

$\}$

if $($tokens$.$size$()\%2==0)$

return false;

try $\{$

result $=$ std::stod$($tokens$[0])$;

for $($size$\_$t i $=1$; i $<$ tokens.size$()$; i $+=2)\{$

std::string op $=$ tokens$[$i$]$;

double nextNum $=$ std::stod$($tokens$[$i $+1])$;

if $($op $=="+")$

result $+=$ nextNum;

else if $($op $=="-")$

result $-=$ nextNum;

else if $($op $=="*")$

result $*=$ nextNum;

else if $($op $=="/")$

result $/=$ nextNum;

$\}$

return true;

$\}$

catch $($const std::exception&$)$

$\{$

return false;

$\}$

$\}$