Mentor session 2/6

Basic data types:

Character:

• how does drRacket display a character? READING
• What is the relationship between the character and the number? ASCII
• What are some “sub-types” of characters? READING, e.g. digit, letter, whitespace
• What are the procedures related to character, and their 6Ps? READING

Number:

• how does drRacket display a number?
• What are some “sub-types” of numbers? How do their differences affect the outcome of any procedures? What do they have in common?
• What are the procedures related to numbers, and their 6Ps? READING

String:

• index and length

    (string-ref str pos) ; count starts from 0
    (substring str start end) ; pay attention to whether the start and end are inclusive or exclusive
    (string-length str) ; count starts from 1
  

  Symbol:

    (symbol? 's) ; A symbol
    (list? '(s)) ; A list
  

  Data Structure:

List:

• not a data type, but a data structure.

    > (symbol? (car '(+ 2 3)))
    #t
  

Higher Order Procedure:

Procedure

• What is a procedure? - function? -method? -algorithm?
• What are the components of a procedure? name of the procedure, parameter, instructions.
• How can we know a variable is a procedure? type in the interactive window and hit enter!

    > (lambda (number) (+ number))
    #<procedure>
  

  then we assign this a name, and then you can use this **unique** name to refer to this .

• How to write a procedure?
• the difference between a procedure and a variable:

    > (define house-grid
        (above (beside (simple-house 20) (simple-house 20))
               (beside (simple-house 20) (simple-house 20))))
      
    > (define house-seq
        (lambda ()
          (beside/align "bottom"
                         (simple-house 10) (simple-house 15)
                         (simple-house 20) (simple-house 25))))
    ; the thing, or the method of computation / transform.
  

• why do we need procedures? Reuse, readability, and abstraction.

section and composition:

Refer to Composition, lambda, and section

Others:

two windows:

• Why do we need a definition window and a interactive window?
• what should go to which? Save for later use → definition window.

Read documentation and understand the error message