I have a code as the following:
list = 
for itr in "Watch out! Hello, world"
How can I convert the above code snippet into an array comprehension? Something like:
[isletter(itr) ? itr : $(give it up) for itr in str]
Maybe you can use a generator expression with the
str = "Watch out! Hello, world"
[ c for c in str if isletter(c) ]
Thanks, your solution works. Inspired by your work, I found another tech:
Be aware that this is a bad idea. It will force your output array to have eltype
Any. In order to initialize an empty vector of characters write:
list = Char
Initializing arrays with a plain
 is a serious performance trap.
Get it! Thanks for your explanations.