Update value of a local variable to new values inside a foreach loop

You cannot change the values of a variable in a rule once assigned. Also, a!save() only works on human interactions/events and hence it won't work. 
You can just create a new dictionary, or array and just assign it to a new variable and consume it. Or directly consume it without assigning it. 

I want to 

remaininamount=principalamount-interest,

principalamount=remainingamount

for each iteration. Could u pls let me know how to do this?

I want to 

remaininamount=principalamount-interest,

principalamount=remainingamount

for each iteration. Could u pls let me know how to do this?

What is your end goal? Tell me your expected output. 

I have a principal loan amount, rate of interest and number of months.

for each month, i want to calculate the interest. once the interest is calculated, the renewed principal will be old principal - interest.

for the next month the interest will be calculated on the renewed principal...and so on...

You could use something like this. 

a!localVariables(
  local!principalAmount: ri!loanAmount,
  local!remainingMonths: ri!tenure - 1,
  local!emi: (
    (local!principalAmount / 100) * ri!interest
  ) / 12,
  {
    { month: 1, emi: local!emi },
    if(
      local!remainingMonths = 0,
      {},
      rule!LoanCalculator(
        loanAmount: local!principalAmount - local!emi,
        tenure: local!remainingMonths,
        interest: ri!interest
      )
    )
  }
)

Hi Harshit, this would not help bcoz the principal remains the same for all the months here. My principal for the second month is principal for first month - interest. Principal for third month is principal for second month-interest. Interest is also calculated based on the renewed principal amount.

That is what we are doing on line 13. Isn't it?

loanAmount: local!principalAmount - local!emi will remain same always right? since local!principalamount and local!emi are same always....

Nope. They'll change with every iteration. This is a recursion. Create an expression rule with the name as 'LoanCalculator' and paste the above definition. Then save it. Should work!

Awesummmmmm! It worked. Thanks Harshit!!!

Hi! I want to use the same practice as Anuradha C , but  in a different context. The logic I am trying to achieve is "if my local variable equals 0, execute this code and make the variable equal to 1 so the next iteration of the forEach loop meets false in the if condition and executes the else code". Is there a way to achieve this with local variables? And if not, how can I make this logic happen?

appian.rocks/.../