Twine Harlow 3 Convert Prompt string to number/integer

Topic: How to accept user input via prompt: and then convert that input into a number.

My set-up:
Twine Version: 2.3.14 (2.3.14)
Story Format: Harlow 3.2.2

(For some reason, I had a difficult time figuring this out - so I’m posting my solution here in case it helps anyone else. Hopefully the long-arms of google will crawl this post)

The trick is to use the ​(num: ) macro
https://twine2.neocities.org/#macro_num

Example
{
(set: $age to (prompt:“How old are you?”, “”))
}

(set: $age2 to (num: $age))
(set: $mathcheck to ($age2 + 10))
the age you entered is $age
converted to a number value: $age2

My math check is $mathcheck (to verify that I now have an integer)

(if: $age2 is <= 18 )[Sorry, you’re too young!]
(else:)[You can continue]

1 Like

Well done.

I have a couple of suggestions, most are optional.

1: Please use the </> option in the comment field Toolbar when including code examples in your posts, it makes those example easier to read / copy-n-paste and stops the forum’s software converting valid Standard quotes into invalid Typographical (curvy) quotes.

eg. wrapping your entire example within </> would result in it looking so…

{
(set: $age to (prompt: "How old are you?", ""))
}

(set: $age2 to (num: $age))
(set: $mathcheck to ($age2 + 10))
the age you entered is $age
converted to a number value: $age2

My math check is $mathcheck (to verify that I now have an integer)

(if: $age2 is <= 18 )[Sorry, you’re too young!]
(else:)[You can continue]

2: You could include the 2nd and 3rd (set:) macro calls within the Collapsing whitespace markup, which would stop them from adding additional blank lines to the example.

3: You don’t need the open and close parentheses/brackets around your $age2 + 10 addition.

4: You shouldn’t use the is keyword comparison operator when using mathematical comparison operators like <= because the is operator means exactly equal to, and logically a value can’t be exactly equal to and less than or equal to at the same time.
note: The only reason your $age2 is <= 18 conditional expression doesn’t result in an error is because Harlowe was enhanced to ignore that specific error.

The following is a variation of your own example with the above suggestions added to it.

{
(set: $age to (prompt: "How old are you?", ""))
(set: $age2 to (num: $age))
(set: $mathcheck to $age2 + 10)
}
the age you entered is $age
converted to a number value: $age2

My math check is $mathcheck (to verify that I now have an integer)

(if: $age2 <= 18)[Sorry, you’re too young!]
(else:)[You can continue]
1 Like

Thanks for the tips, Greyelf!