This is my first post here; correct me if I am doing anything wrong.
My question is: how can I check if number is an integer? Do I have to create a custom function or is there a built - in function for that?
If there is no built - in function, that's what I've made so far (edit: just realised I can't use floor like that):
(I am new with functions in MIT App Inventor, so didn't know how to set 'boolean' to a value. Correct me if I am doing anything wrong.)
Floor rounds input to the larger number not greater than the input so for example 24.12 results 24 , but 24.12 is not an integer. Try checking if contains . or , (in my country for example decimals are separeted with comma)
yea, just realised that.
Is there a way to return true or false based on the result (so when I call IsInteger(numberHere) it would return true or false)?
Also how can I enable ? hints on blocks?
Thanks for the code. I will see if it works soon.
While you were not responding, I remixed your first code and come up with this:
Also how can I make the ? marks on blocks show up so I can know the result?
This probably works but I would prefer to use the solution that returns true / false, not a string value.
Your solution should work so I am going to mark it 
Procedure returns true/false, I just used less blocks 
Oh ye, I see. Thanks for posting! (I will use your solution)
I would also go with doing initialize local result to false. It used to return an empty string when object (number) wasn't a number.
Doing this is pointless, I think. Just replace initialize local result to (empty string) from the solution with initialize local result to false. Few blocks less, the same result.
...just one less 'else', but yes, that would be optimum.
If the source of a number is a TextBox, setting it to NumbersOnly helps, providing a decimal point is used for floats, not a comma.
IsIntegerTest.aia (2.5 KB)
Or:
That's vastly superior Tim!
Begs the question though as to why we do not have a maths block for this....
I don't know if there was ever a discussion for/against such a block. I think the argument for would be that it simplifies some things, but the argument against would mainly be to try and keep the blocks language somewhat constrained. I could imagine a good compromise would be modifying the is number? to have a dropdown where you could choose different constraints to check.
FYI, the more appropriate implementation of isInteger would be:
Modifying the block would be a good idea. One could also add a check to see if the number is a HEX number.
(Beating a dead horse)
No one used a test with a negative number to rule out the floor-based attempts.
There's no such thing as a hex number in App Inventor. It could be a text block that contains hexadecimal, but technically all number blocks are binary numbers rendered as decimal numbers.
