I'm a swift beginner, since then I wrote objective-c code.
I bought the not so small book Swift 5 and run with the second snippet against the wall:
for x in 1...100
let y = sin(Double(x) / 10)
print("X=(x), y=(y) ")
I got the error : "Use of unresolved identifier 'sin"
The solution is a missing underscore (_sin), blame it to the book
I hope you like to support me in the next future