I have multiple buttons 0 to 9 and other calculation methods like plus, minus, etc
There are two display items, Memory and Display; Memory item is hidden.
When click on 1 button then display value 1 in Display item. When click on + button then store value 1 in Memory item. When click on = button then add Memory + Display values and show answer on Display item.
Question is how to code multiple calculation in equal to = button?
You have three registers: the button clicked, the display value and the memory value. So the calculation string 2+3=5 looks something like this:
button Display Memory
2 2
+ 2 2
3 3 2
= 5 5
As I understand your question, you want to handle a longer calculation, when the user types in several steps without pressing =, for instance 2+3+7/4*5=. There are several ways to do this, but the most intuitive one for the user is to treat the arithmetic operators as having an implicit = operation, calculating the running sum and displaying that value.
button Display Memory
2 2
+ 2 2
3 3 2
+ 5 5
7 7 5
/ 12 12
4 4 12
* 3 3
5 5 3
= 15 15
To make this work you need another register item to track the current operator.
button Display Memory Operator
2 2
+ 2 2 +
3 3 2 +
+ 5 5 +
7 7 5 +
/ 12 12 /
4 4 12 /
* 3 3 *
5 5 3 *
= 15 15 =
So when the user clicks a triggering button you execute something like this:
if :operator = '+' then
:memory := :memory + :display;
elsif :operator = '-' then
:memory := :memory - :display;
elsif :operator = '/' then
:memory := :memory / :display;
elsif :operator = '*' then
:memory := :memory * :display;
end if;
:display := :memory;
:operator := :button_value;
You will need to decide how to handle the situation when the user types two operations in a row e.g. +/. But probably you need to track previous button press too.
So what is the purpose of =? Well, it depends on what the user types next. If they follow = with another operator then it's just a subtotal and the sum continues....
button Display Memory
2 2
+ 2 2
3 3 2
= 5 5
+ 2 5 <-- continue with existing sum
= 7 7
... but if they follow it with a number then we're starting a new sum and we reset the memory:
button Display Memory
2 2
+ 2 2
3 3 2
= 5 5
2 2 <-- start a new sum
+ 2 2
2 2 2
= 4 4