Can someone explain how this recursive function works step by step?

function outvar = recurfn(num) % Format: recurfn(number)

if num < 0

outvar = 2;

else

outvar = 4 + recurfn(num-1);

end

end

Can someone explain to me how this recursive function works step by step?

for example without using MATLAB how would i figure out the result of recurfn(1) or recurfn(2)?

Thanks!

Answer 1

[Stephane]

You simply add the sequence over and over (decreasing num by 1 each time), up until you reach the stop signal (num < 0).

This gives

recurfn(2) = 4 + recurfn(1)

= 4 + [ 4 + recurfn(0) ]

= 4 + 4 + [ 4 + recurfn(-1) ]

= 4 + 4 + 4 + 2

[AStar]

Thanks!

Answer 2

[Jesus Sanchez]

function outvar = recurfn(num) % Format: recurfn(number)
    if num < 0 
        outvar = 2;
    else
        outvar = 4 + recurfn(num-1);
    end 
end

As fas as I understand this, the function will call itself forever until num has a value less than 0. Thus, outvar is fixed to 2.

[AStar]

Thanks for your answer, but I dont think you understand my question. I am asking for an explanation of the logic required to answer this question without using the MATLAB software. How can one determine for example recurfn(2), recurfn(4) etc without actually calling those in the command window.

[Jesus Sanchez]

See answer of Stephane. I am wrong