String to int conversion using toInt function

Question

I am trying to convert a string to integer using String.toInt. However, when I want to bind the result to a variable and then do some simple math with it I get this error:

Function add is expecting the 2nd argument to be:

Int

But it is:

Result String Int

How can I just extract the integer part of the result?

Answer 1

toInt can fail in parsing. You need to check it using a case statement:

case toInt str of
  Err msg -> ... -- do something with the error message
  Ok val -> ... -- val is an Int which you can add

More about Result here