racket lambdas

all_study_guide.tex

@@ -155,7 +155,19 @@ We can navigate these with car for first element, cdr for tail, cadr for head of
         \subsubsection{Properties}
         Structs in Racket, like objects in OOP, are pass-by-pointer -- so, (if they are mutable), we can set their fields
         but when we reassign the original struct is unchanged.
-
+        \subsection{Lambdas}
+        Lambdas are good not only for delaying evaluation and implementing lexical closures, but 
+        also because you can use them to do multiple things in a row. \\
+
+        Question: Write a function map-pairs that takes in a function and a list of kvpairs and mutates
+the pairs such that the new value for each pair is the function applied to their original
+values.
+        \begin{minted} 
+        (define (map-pairs f ls)
+            (if (null? ls)
+                '()
+                ((lambda () (set-kvpair-value! (car ls) (f (kvpair-value (car ls)))) (map-pairs f (cdr ls))))))
+        \end{minted}
 \section{Prolog}
 \subsection{Rules, facts, and goals}
     A fact is a predicate, and a rule is an extension of a fact with added clauses: