How to cast any variable to char?

I just have this simple line

gwa_list-key = sy-tabix. (the index here were set to last character hence i need to delete leading space)

SHIFT gwa_list-key LEFT DELETING LEADING space.

is it possible to do this in a one liner? i have tried doing CAST but returned - Unexpected operator "CAST".

gwa_list-key = cast #( sy-tabix )