;; 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-beginner-reader.ss" "lang")((modname lect04) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ())))
#| Recall: Examples of primitive data:
 number       34    34.5   #i3.14
 string       "hello"
 char         #\A   #\space
 boolean      #t  #f
 symbol       'green  'read-only

 (...regexp  #rx"[0-9]*", images, ports, ...)
 |#


#| Recall: some built-in functions and their signatures (types):
                           Signature                         Example
   substring  :     string, natnum, natnum -> string  (substring "hello" 1 4) = "ell"
   string-ref :     string, natnum -> char            (string-ref "hello" 1)  = #\e
   string-length :  string -> natnum                  (string-length "hello") = 5
   string-append :  string, string -> string          (string-append "hel" "lo") = "hello"
   =          :     number, number -> boolean         (= 4 (+ 2 3))  = false
   string=?   :     string, string -> boolean         (string=? "ell" (substring "hello" 1 4)) = true
   string?    :     ANY -> boolean                    (string? 43) = false

 |#

#| Can use 'define' to bind an identifier to a value: |#
(define n 37)
(define name "Ian B-meister")

; Note the following are identifers:  `false`; `+`



#| The Design Recipe (take 1 -- primitive types only)

  ------- per function:
    4. tests
    5. stub : signature, head, description, body
    7. complete the body-expression
    8. watch your tests pass
|#

; triplify : number -> number
; Triple a given number.
;
(define (triplify n)
  (* n 3))

(check-expect (triplify 5) 15)
(check-expect (triplify -1.5) -4.5)


; New syntax: `define` for functions.
; Note how it mirrors how the function is called (but params instead of argument-expressions).




(check-expect (triplify 0)  0)
; You: write:
; monogram: given a first name and last name, return a monogram with initials:
; (monogram "Ian" "Barland") -> "i.b."
(check-expect  (monogram "Ian" "Barland") "i.b.")
(check-expect (monogram "Jay" "Z") "j.z.")

; monogram : string, string -> string
; Construct a monogram from the first initials of `first-name`, `last-name` names.
; `first-name` and `last-name` must be non-empty.
;
(define (monogram first-name last-name)
  (string-append (string (char-downcase (string-ref first-name 0)))
                 "."
                 (string (char-downcase (string-ref last-name  0)))
                 "."))

  ; Note -- you're not expected to know about `string-ref`, `char-downcase`, `string` --
  ; those are things you'd learn, when you need them, scouring through the documentation.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

; A Re-factored version, once we have `initialize`:
(define (monogram first-name last-name)
    (string-append (initialize first-name)
                   (initialize last-name)))


; initialize : string -> string
; Return the first letter of `wrd` downcased, following by ".".
;
(define (initialize wrd)
  (string (char-downcase (string-ref wrd 0))
          #\.))

(check-expect (initialize "hello") "h.")
(check-expect (initialize "X") "x.")

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

#|
; In full racket -- just as a teaser:
; Once we have `initialize` making acronyms not so bad:

; acronymize : string -> string
; Return an acronym of `str`: the first initial of each word.
;
(define (acronymize str)
  (apply string-append (map initialize (regexp-split #px"\\s-" str))))

(module+ test
  (require rackunit)
  (check-equal? (acronymize "Light-amplified stimulated emisssion radiation") "l.a.s.e.r.")
  (check-equal? (acronymize "Radio and detecting and ranging") "r.a.d.a.r.")  ;also, 'sonar'.
  (check-equal? (acronymize "self-contained underwater breathing apparatus") "s.c.u.b.a.")
  )
|#