An Introduction to Functional Programming Through Lambda Calculus

- 121 -["Betty","Baker"].For example, we might represent a stock item consisting of a string , an integer and an integer as the list:[,,]for example:or["VDU",25,10]["modem",12,15].For example, we might represent a telephone directory entry consisting of a composite value name as above, a string and an integer as a list:[[,],,]for example:or[["Anna","Able"],"Accounts",1212][["Betty","Baker"],"Boiler room",4242]Now, a sequence of composite values will be represented by a list of lists, for example a circulation list:[["Anna","Able"],["Betty","Baker"],["Clarice","Charlie"]]or a stock list:[["VDU",25,10],["modem",12,15],["printer,250,7]]or a telephone directory:[[["Anna","Able"],"Accounts",1212],[["Betty","Baker"],"Boiler room",4242],[["Clarice","Charlie"],"Customer orders",1234]]7.3. Processing composite values sequencesWe are using linear lists to represent composite value sequences so we will now look at the use of linear listalgorithms to process them.For example, suppose that given a circulation list we want to find someone’s forename from their surname. If the listis empty then return the empty list. If the list is not empty then if the surname matches that for the first name in the listthen return the corresponding forename. Otherwise, try looking in the rest of the list.rec NFIND S [] = []or NFIND S (H::T) =