Incorrect or inconsistent behavior with sπ‘ πβ method
joeskeen opened this issue Β· comments
Consider the following unit tests:
π¦ testtube π
π β‘οΈ π’ π
β©οΈ πππ¦βοΈβοΈ
π
π π¦ π§ͺ π
βοΈ βοΈ π π
π’π πΊππ€ABCDEFGHIπ€ π€Fπ€β 5 π€'F' should be at index 5 of 'ABCDEFGHI'π€β
π‘π πͺπ€ABCDEFGHIπ€ 1 3β π€BCDπ€ π€substring of 'ABCDEFGHI' from index 0 and length 3 should be 'BCD'π€β
π’π πΊππ€πΏABCπcπ€ π€ππ€β 4 π€'π' should be at index 5 of 'πΏABCπc'π€β
π‘π πͺπ€πΏABCπcπ€ 1 3β π€ABCπ€ π€substring of 'πΏABCπc' from index 0 and length 3 should be 'ABC'π€β
π
π
All these tests should pass, but this is the output:
β Failed 'π' should be at index 5 of 'πΏABCπc' but it is 7
4 assertions, 1 failures
From this message, it is apparent that the sπ‘ πβ method is returning the index in terms of UTF-8 bytes, not grapheme index. This is inconsistent with the sπ‘ πͺβmethod, which is using grapheme index (as shown in the tests).
This inconsistency makes the sπ‘ πβmethod confusing at best and useless at the worst case when strings are outside of the ASCII range.
Ideally the workaround for this issue would be to first convert the string into a list via sπ‘ πΆβ, then find the index with sπ¨ πβ, but unfortunately that does not exist. I intend to submit a pull request for that method shortly.
Edit: you can't implement πβ on sπ¨πβͺπ since you can't compare two βͺs with π or anything else, and you can't cast the βͺ to protocol π since it's generic π’. Looks like the only way to do this is fix the sπ‘πβ method.
I agree, this is very inconsistent and should be corrected.