Programming languages:

Given the definition of the foldr(or reduce) function as:

foldr: f x NIL = x foldr: f x (cons a list) = f a (foldr f x list) and gave an example of using foldr. Let's have some fun and combine the features of a number of different languages. (1) Borrowing from the course notes and Haskell, let's define a function foldl, (a) foldl f x NIL = x (2) Borrowing from Python, we can treat a string as a sequence (i.e. a list) of characters, "bar" ('b', 'a', 'r') ['b', 'a', 'r'] (3) Borrowing from Lisp, we can use cons cells to represent or create lists, ('b', 'a', 'r') (cons 'b' (cons 'a' (cons 'r'))) (4) Borrowing from Fortran, we can define a string concatenation function, //'concate'//'nation' 'concatenation' (5) Borrowing from Scheme, define a toggle function, f x y = f y x, (define toggle (lambda (f x y) (f y x))) That is, the toggle function switches its arguments, in Lambda Calculus, it's, lambda_f, lambda_x, lambda_y, f y x Thus, for example, (f 'back' 'drop') (f 'drop' back') In this question, please trace the execution/reduction of the following function: foldl (toggle//) nil ("foo" "bar" "baz") In order to obtain full credit and possibly obtain partial credit when appropriate, you must show each step (for example, my solution has 11 steps). At each step, briefly describe how you transitioned from the previous step. For example, you simply explain it by listing: via OR via (1)(a)