On 1/2/2018 12:43 PM, Sanjeeb Sinkhada wrote:

hi could anyone help me with this question?Write a function that will take a list of pairs and return just thepair comprising the first element of the first pair and the secondelement of the last pair.Eg. > (reduce-pairs ’()) NIL > (reduce-pairs ’((1 2) (3 4))) (1 4) > (reduce-pairs ’((1 2) (3 4) (5 6))) (1 6)I have got this so far (define reduce-pair(λ(x y)(cond ((pair? x)x) (cons( car x) (cons ( list-tail (second y))))))) but its completely wrong thanks in advance

`Yup, it definitely is wrong. <grin> This smells like homework and the`

`homework policy in this forum is to help but not answer directly.`

`First, your examples have a single list argument, but your function is`

`defined to have 2 arguments. Why?`

`Second, what should happen if the list contains only 1 pair or contains`

`elements that are not pairs?`

`Third, are you supposed to solve the problem by walking the list, or can`

`you use any pre-defined list functions?`

`Think about how you would get the first and last elements of the list.`

`Then think about how you get the first and second values of those`

`pairs. Then think about how to make a new pair from those values. If`

`you can use any predefined function, then you're at least half way there`

`already ... you just need to put it together.`

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