An Introduction to Functional Programming Through Lambda Calculus

- 100 -Note that the comparison depends on the type of the list elements.Suppose we are deleting from a linear list of numbers. For example, suppose we want to delete 3from the list:we use:[1,2,3,4]DELETE 3 [1,2,3,4] -> ... ->CONS 1 (DELETE 3 [2,3,4]) -> ... ->CONS 1 (CONS 2 (DELETE 3 [3,4])) -> ... ->CONS 1 (CONS 2 [4]) -> ... ->CONS 1 [2,4] ==[1,2,4]In our notation, the function becomes:rec DELETE V L =IF ISNIL LTHEN NILELSEIF EQUAL V (HEAD L)THEN TAIL LELSE (HEAD L)::(DELETE V (TAIL L))For example, suppose we want to delete 10 from:we use:[5,10,15,20]DELETE 10 [5,10,15,20](HEAD [5,10,15,20])::(DELETE 10 (TAIL [5,10,15,20])) -> ... ->5::(DELETE 10 ([10,15,20]))5::(TAIL [10,15,20]) -> ... ->5::[15,20] => ... =>[5,15,20]Note again that implicit list head and tail selection in the case notation ie replaced by explicit selection in our currentnotation.6.9. List comparisonTwo lists are the same if they are both empty: