;; The first three lines of this file were inserted by DrRacket. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-intermediate-lambda-reader.ss" "lang")((modname oct12-dist-part3) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ())))
; functions are values.
; That is, we can pass them into functions (as arguments),
; and we might even get them back as a result from calling a function.

(define l372 (cons 3 (cons 7 (cons 2 '()))))

(sort l372 <)

(define names (cons "steven" (cons "mark" (cons "ashenafi" (cons "christoper" '())))))
(sort names string>?)

; second-letter<? : string, string -> boolean
; ASSUME both strings have at least two letters.
;
#;(define (second-letter<? strA strB)
  (char<? (string-ref strA 1)
          (string-ref strB 1)))

; the above `(define (second...` is syntactic sugar for the following:
;
(define second-letter<? (λ (strA strB) (char<? (string-ref strA 1)
                                               (string-ref strB 1))))

(check-expect (second-letter<? "helllo" "bye") #true)
(check-expect (second-letter<? "hélllo" "bye") #false)

(sort names second-letter<?)
(sort names (lambda (strA strB) (char<? (string-ref strA 1)
                                        (string-ref strB 1))))

(sort (cons "steven" (cons "mark" (cons "ashenafi" (cons "christoper" '()))))
      (λ (strA strB) (char<? (string-ref strA 1)
                             (string-ref strB 1))))

#| // Passing functions in Java (kinda):

        String[] bands = new String[]{"The Cars", "Bishop Allen", "The Police"};
        System.out.println(Arrays.toString( bands ));

        /*   The pre-Java-8 way: to pass code, pass an object with one method:
             (or at least, one method which the receiver knows to call).
             It can be an anonymous sub-class, if you want to do it inline:

        Comparator<String> myComp = new Comparator<String>() {
                                       public int compare( String strA, String strB ) {
                                           return strA.charAt(1) - strB.charAt(1);
                                           }
                                        };
        Arrays.sort( bands, myComp );
        System.out.println(Arrays.toString( bands ));

        // Java 9 provides v.nice syntactic sugar for the above:
        Arrays.sort( bands, (strA,strB) -> strA.charAt(1) - strB.charAt(1); );
        // You can use this short-hand whenever the recipient wants an object
        // which has only one method.  If you provide raw code, Java can figure
        // out how to make it into an object of a class which has your code
        // as its one method.  (They call it a "functional interface".)
        System.out.println(Arrays.toString( bands ));

        Arrays.sort( bands, String::compareTo );
        System.out.println(Arrays.toString( bands ));
|#