Search code examples
stringparsingnetlogonumeric

How can I parse a string in Netlogo?

Context

For my model I would like to have an input where the user can enter a series of values.

E.g.

enter image description here

What I would like to have from the input shown above is a list of five numbers, e.g. [0.5 0.2 0 0.2 0.5], so I can then use the numbers that they enter for some calculations.

The problem

Unfortunately, having an input set up like above will spit out "0.5 0.2 0 0.2 0.5" if I set the type to be a string. If I set the type to numeric, it will only allow a single number to be entered.

So, how can I parse the string the basis of a space (i.e. " ")? I am open to alternatives too, although I would prefer to keep it in Netlogo (e.g. not reading in a text file of values) to make it easier to change, as it is something that I suspect will get played around with a lot.

What I have tried

I have tried using read-from-string, but it also doesn't like a series of numbers entered like above. I also attempted to use the explode function from the string extension (https://github.com/NetLogo/String-Extension), but my version of Netlogo (6.2.0) did not like the API from that extension and wouldn't allow me to use it.

I am very new to NetLogo, so sorry if my question is silly or I have not made something clear!

Solution

  • As per the docs on it, read-from-string can parse a list of literal values. The issue you are having is that a NetLogo list literal must have square brackets to open and close, as per the Constant Lists section of the Programming Guide. So all you need to do is add [ and ] to your user's input.

    to test
  let s "0.5 0.2 0 0.2 0.5"
  let l read-from-string (word "[" s "]")
  show l
  show item 2 l
end

    Output:

    observer> test
observer: [0.5 0.2 0 0.2 0.5]
observer: 0

    I would caution, though, that it would be very easy for users to enter numbers with a different format, like 0, 2, 3, 5.0, using commas to separate values. A check that the conversion actually worked would be wise, as the error message you'd get from the failed read-from-string probably wouldn't be helpful to the model user.