simple calculator using GUI

I tried to make a simple calculator with GUI.

For that purposes i want to take the input as string.then convert this string into number ,and then perfom the operation.

For instance i would like to take input like

("5+6/3")

and then using str2num i want to perform that operation.

In all button i use almost the same code like ( here i show the code for button 1 and divison sign.)

% --- Executes on button press in division.
function division_Callback(hObject, eventdata, handles)
% hObject    handle to division (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'/'));


% --- Executes on button press in button1.
function button1_Callback(hObject, eventdata, handles)
% hObject    handle to button1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'1'));

In equal button

% --- Executes on button press in equal.
function equal_Callback(hObject, eventdata, handles)
% hObject    handle to equal (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
p = str2num(s);  % it will convert the string in mathmatical expression then perform the operation
set(handles.screen,'string',num2str(p));

It didn't show the expected output.

What to change in equal Button?

Thanks in Advance.

Answer 1

[Rik]

For general advice and examples for how to create a GUI (and avoid using GUIDE), have look at this thread.

Every callback is a separate function that doesn't know what happened in the other functions. That means the variable s doesn't exist.

function equal_Callback(hObject, eventdata, handles)
s=get(handles.screen,'string');
p = str2num(s);  % calls eval implicitly
set(handles.screen,'string',num2str(p));

You should be really careful with str2num. It calls eval, meaning it can execute arbitrary code. You should avoid it when possible. In this case it is safe, as long as the user doesn't type any code in the text box.

[Md. Ashikur Rahman Any]

Thanks it worked

Answer 2

[Ngo Nguyen]

I think you should use the function: eval

[Md. Ashikur Rahman Any]

It didn't work.

[Ngo Nguyen]

At first, check your equal_Callback, what is s?

When you start a new function, the parameter "s" is no longer exist?

What kind of the error message did you get?

Answer 3

[Md. Ashikur Rahman Any]

function varargout = ExCal(varargin)
% EXCAL MATLAB code for ExCal.fig
%      EXCAL, by itself, creates a new EXCAL or raises the existing
%      singleton*.
%
%      H = EXCAL returns the handle to a new EXCAL or the handle to
%      the existing singleton*.
%
%      EXCAL('CALLBACK',hObject,eventData,handles,...) calls the local
%      function named CALLBACK in EXCAL.M with the given input arguments.
%
%      EXCAL('Property','Value',...) creates a new EXCAL or raises the
%      existing singleton*.  Starting from the left, property value pairs are
%      applied to the GUI before ExCal_OpeningFcn gets called.  An
%      unrecognized property name or invalid value makes property application
%      stop.  All inputs are passed to ExCal_OpeningFcn via varargin.
%
%      *See GUI Options on GUIDE's Tools menu.  Choose "GUI allows only one
%      instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES

% Edit the above text to modify the response to help ExCal

% Last Modified by GUIDE v2.5 19-Apr-2021 09:57:22

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @ExCal_OpeningFcn, ...
                   'gui_OutputFcn',  @ExCal_OutputFcn, ...
                   'gui_LayoutFcn',  [] , ...
                   'gui_Callback',   []);
if nargin && ischar(varargin{1})
    gui_State.gui_Callback = str2func(varargin{1});
end

if nargout
    [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
    gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT


% --- Executes just before ExCal is made visible.
function ExCal_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   command line arguments to ExCal (see VARARGIN)

% Choose default command line output for ExCal
handles.output = hObject;

% Update handles structure
guidata(hObject, handles);

% UIWAIT makes ExCal wait for user response (see UIRESUME)
% uiwait(handles.figure1);


% --- Outputs from this function are returned to the command line.
function varargout = ExCal_OutputFcn(hObject, eventdata, handles) 
% varargout  cell array for returning output args (see VARARGOUT);
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Get default command line output from handles structure
varargout{1} = handles.output;



function screen_Callback(hObject, eventdata, handles)
% hObject    handle to screen (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'String') returns contents of screen as text
%        str2double(get(hObject,'String')) returns contents of screen as a double


% --- Executes during object creation, after setting all properties.
function screen_CreateFcn(hObject, eventdata, handles)
% hObject    handle to screen (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit controls usually have a white background on Windows.
%       See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
    set(hObject,'BackgroundColor','white');
end


% --- Executes on button press in button8.
function button8_Callback(hObject, eventdata, handles)
% hObject    handle to button8 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'8'));



% --- Executes on button press in button7.
function button7_Callback(hObject, eventdata, handles)
% hObject    handle to button7 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'7'));



% --- Executes on button press in button9.
function button9_Callback(hObject, eventdata, handles)
% hObject    handle to button9 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'9'));


% --- Executes on button press in button5.
function button5_Callback(hObject, eventdata, handles)
% hObject    handle to button5 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'5'));


% --- Executes on button press in button4.
function button4_Callback(hObject, eventdata, handles)
% hObject    handle to button4 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'4'));


% --- Executes on button press in button6.
function button6_Callback(hObject, eventdata, handles)
% hObject    handle to button6 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'6'));


% --- Executes on button press in button2.
function button2_Callback(hObject, eventdata, handles)
% hObject    handle to button2 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'2'));


% --- Executes on button press in button1.
function button1_Callback(hObject, eventdata, handles)
% hObject    handle to button1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'1'));


% --- Executes on button press in button3.
function button3_Callback(hObject, eventdata, handles)
% hObject    handle to button3 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'3'));


% --- Executes on button press in zerroo.
function zerroo_Callback(hObject, eventdata, handles)
% hObject    handle to zerroo (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'0'));


% --- Executes on button press in dott.
function dott_Callback(hObject, eventdata, handles)
% hObject    handle to dott (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'.'));


% --- Executes on button press in pipi.
function pipi_Callback(hObject, eventdata, handles)
% hObject    handle to pipi (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'pi'));


% --- Executes on button press in sqrtt.
function sqrtt_Callback(hObject, eventdata, handles)
% hObject    handle to sqrtt (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)


% --- Executes on button press in square.
function square_Callback(hObject, eventdata, handles)
% hObject    handle to square (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)



% --- Executes on button press in equal.
function equal_Callback(hObject, eventdata, handles)
% hObject    handle to equal (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

p = eval(s);
set(handles.screen,p);


% --- Executes on button press in resettt.
function resettt_Callback(hObject, eventdata, handles)
% hObject    handle to resettt (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
set(handles.screen,'string',' ');
clear all ;


% --- Executes on button press in division.
function division_Callback(hObject, eventdata, handles)
% hObject    handle to division (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'/'));


% --- Executes on button press in multiply.
function multiply_Callback(hObject, eventdata, handles)
% hObject    handle to multiply (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'*'));


% --- Executes on button press in minus.
function minus_Callback(hObject, eventdata, handles)
% hObject    handle to minus (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'-'));


% --- Executes on button press in plus.
function plus_Callback(hObject, eventdata, handles)
% hObject    handle to plus (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'+'));


% --- Executes on button press in xval.
function xval_Callback(hObject, eventdata, handles)
% hObject    handle to xval (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'x'));


% --- Executes on button press in yval.
function yval_Callback(hObject, eventdata, handles)
% hObject    handle to yval (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
s=get(handles.screen,'string');
set(handles.screen,'string',strcat(s,'y'));


% --- Executes on button press in simulate.
function simolte_Callback(hObject, eventdata, handles)
% hObject    handle to simolte (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)



function practice_Callback(hObject, eventdata, handles)
% hObject    handle to practice (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'String') returns contents of practice as text
%        str2double(get(hObject,'String')) returns contents of practice as a double


% --- Executes during object creation, after setting all properties.
function practice_CreateFcn(hObject, eventdata, handles)
% hObject    handle to practice (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit controls usually have a white background on Windows.
%       See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
    set(hObject,'BackgroundColor','white');
end

[Ngo Nguyen]

Please check parameter s in your equal function. What is s?

[Md. Ashikur Rahman Any]

Unrecognized function or variable 's'.

Error in ExCal>equal_Callback (line 230)
p = eval(s);

Error in gui_mainfcn (line 95)
        feval(varargin{:});

Error in ExCal (line 42)
    gui_mainfcn(gui_State, varargin{:});

Error in
matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)ExCal('equal_Callback',hObject,eventdata,guidata(hObject)) 
Error while evaluating UIControl Callback.

Unrecognized function or variable 's'.

Error in ExCal>equal_Callback (line 230)
p = eval(s);

Error in gui_mainfcn (line 95)
        feval(varargin{:});

Error in ExCal (line 42)
    gui_mainfcn(gui_State, varargin{:});

Error in
matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)ExCal('equal_Callback',hObject,eventdata,guidata(hObject)) 
Error while evaluating UIControl Callback.

Unrecognized function or variable 's'.

Error in ExCal>equal_Callback (line 230)
p = eval(s);

Error in gui_mainfcn (line 95)
        feval(varargin{:});

Error in ExCal (line 42)
    gui_mainfcn(gui_State, varargin{:});

Error in
matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)ExCal('equal_Callback',hObject,eventdata,guidata(hObject)) 
Error while evaluating UIControl Callback.

Unrecognized function or variable 's'.

Error in ExCal>equal_Callback (line 230)
p = eval(s);

Error in gui_mainfcn (line 95)
        feval(varargin{:});

Error in ExCal (line 42)
    gui_mainfcn(gui_State, varargin{:});

Error in
matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)ExCal('equal_Callback',hObject,eventdata,guidata(hObject)) 
Error while evaluating UIControl Callback.

This is the error msg

[Md. Ashikur Rahman Any]

s is the string what we have give input so far.

like if we press

"5+6"
this "5+6" will be stored in s.
and if i convert this s to number than it should return 5+6 =11

[Md. Ashikur Rahman Any]

You can make me correct.What code i should write for equal button?

Answer 4

[Md. Ashikur Rahman Any]

I want to add a plot with that calculator like

My plan is to write the expression and converting this string to symbolic variable than plotting the equation.

But it didn't work properly.what to do?

% --- Executes on button press in Plott.
function Plott_Callback(hObject, eventdata, handles)
% hObject    handle to Plott (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

grp=get(handles.screen,'string');
global syms x y;
axes(handles.axes1);
x=0:0.1:10;
y=str2sym(grp);

fplot(y,[-10 20]);
guidata(hObject,handles);

[Rik]

You should not rely on global variables. You have the handles struct right there to share data between callbacks.

You should also consider storing handles.screen.String separately (and restore it every callback that changes it). That way you can avoid malicious input.