An elderly professor who has only ever programmed in FORTAN$77$ and C decides to

re$-$implement a function in C$++.$ The new program is to be written using modern

C$++$ memory management and collections from the Standard Template Library.

The result, along with a short test program, is as follows:

$1//$ File: dblsum.h

$2$ #include

$3$ #include

$4$

$5$ int dblsum$($std::unique$\_$ptr$>$&$)$;

$1//$ File: dblsum.cxx

$2$ #include

$3$ #include

$4$

$5$ int dblsum$($std::unique$\_$ptr$>$& a$)$

$6\{$

$7$ return $2*((*$a$)[0]+(*$a$)[1])$;

$8\}$

$9$

$10$ #include

$11$ int main$()$

$12\{$

$13$ auto a$\_$ptr $\{$

$14$ std::make$\_$unique$>($

$15$ std::array$(\{3,-5\})$

$16)$

$17\}$;

$18$ std::cout $<<$ dblsum$($a$\_$ptr$)<<$ std::endl;

$19$ return $0$;

$20\}$

$($Line numbers are for reference only and are not part of the code$).$

Question continues on the next page...

Page $5$ of $8$ Continued Overleaf

$($a$)$ Write out the type of dblsum in full in English words, including the type of its

argument. $[5]$

$($b$)$ Why must the argument to this function be passed as a reference? $[1]$

$($c$)$ What is the advantage of passing a reference to an array constant rather than

passing an array variable? $[2]$

$($d$)$ What is the type of $(*$a$)$ on line $7?[2]$

$($e$)$ In lines $1416,$ a constant array object containing two integers is constructed

from a variable array object containing two integers. Is this allowed? If so$,$

explain why. $[2]$

$($f$)$ FORTRAN$77$ passes all function arguments by reference. The professor$$s postgraduate student told him that was the same as passing a pointer in C$++.$

Do you agree with the post$-$graduate student? If not, explain the difference

between passing a pointer and passing a reference. $[3]$

$($g$)$ The code could be simplified but achieve the same design aims by changing

the type of dblsum. Rewrite the function using a simpler convention, and

show how the test program would have to be modified to accommodate the

change. $[8]$

$($h$)$ The make$\_$unique function on lines $1416$ allocates a new array on the heap.

Is the allocated memory freed, and if so$,$ when?