Success: string_length("Peter ",X). (gives X=6). string_length("Peter ",6). string_length("401.35",6). Fail: string_length("Peter",6). Error: string_length(Str,Len). (Error 4). string_length(Str,6). (Error 4). string_length("small",5.0). (Error 5). string_length(Str,instantiated). (Error 5). string_length(Str,46.2) (Error 5). string_length('this one',L). (Error 5).