Recursive Procedure in Lists Data Structure

Question

This is a procedure to return the last item in a list 1:

proc last (1)
if    (isEmpty(1))
       error('Oops. Empty list in procedure last.')
elseif (is empty(rest1))
       return (first(1)
else   return last(rest(1))

Modify that to create a recursive procedure getItem(i,l) that returns item i in a list 1, where i is an integer greater than zero.

proc getItem(i,1)
if    (isEmpty(1))
      error('Opps. Empty list in procedure last.')
else if (isEmpty(getItem,i1)
else if i > 0
      return item(i,1)

is that correct?

Yochai Timmer · Accepted Answer · 2011-02-03 21:21:11Z

1

For it to work recursively, that last line needs to have the same name of the function.

Besides that, you need to decrease i .... otherwise you aren't moving...

should be something like:

proc getItem(i,1)
if    (isEmpty(1))
      error('Opps. Empty list in procedure last.')
else if (i > 0)
     return getItem(i-1,1)
else return first(1)

answered Feb 3, 2011 at 21:21

Yochai Timmer

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Comments

speedplane · Accepted Answer · 2011-02-03 21:18:34Z

0

What language are you using? In most languages you cannot use numbers as variable names. Also, you're missing a couple of parenthesis and you're not using 'else if' consistently.

answered Feb 3, 2011 at 21:18

speedplane

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