If String is instantiated, unifies List with the list whose elements are the ASCII codes for the elements of the string.
If List is instantiated, unifies String with the string corresponding to this list of ASCII codes.
Success: string_list(S,[65,98,99]). (gives S="Abc"). string_list("abc",L). (gives L=[97,98,99]). string_list("abc",[97,A,99]). (gives A=98). string_list(S,[127]). (gives S=""). string_list("abc",[97|A]). (gives A=[98,99]). Fail: string_list("abc",[98,99,100]). Error: string_list(S,[A|[128]]). (Error 4). string_list(S,[1|A]). (Error 4). string_list('string',L). (Error 5). string_list(S,"list"). (Error 5). string_list('string',[128]). (Error 5). string_list(S,["B"]). (Error 5). string_list(S,[256]). (Error 6).