code for equal to '=' in oracle forms calculator?

Question

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?

Answer 1

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