Land of Lisp 👷🏼‍♂️👷🏼‍♀️

Lisp Keywords

Setting Values

• defparameter - defines a mutable global value (can be changed by further calls to defparameter)
• defvar - defines an immutable global value (cannot be changed by further calls to defvar but can be changed by setf)
• setf - sets a value, e.g. (setf *my_number* 5)

List Keywords

• cons - creates a list from two items (one of which can be nil)
• car - returns the head of a list
• cdr - returns the tail of a list
• list - creates a list, e.g. (list 1 2 3) creates the list (1 2 3)
• member - returns the tail of a list when an item is found e.g. (member 1 '(3 4 1 5)) will return (1 5)
• assoc
• find
• remove-if
• remove-if-not

Lists - Higher Order Functions

• apply
• mapcar - maps function to each item in list

> (mapcar #'print '(a b c))
A
B
C

• maplist - maps function to a list of each item in list

> (maplist #'print '(a b c))
(A B C)
(B C)
(C)

Maths Keywords

• expt - exponential, e.g. (expt 2 3) returns 8
• ash - arithmetic shift e.g (ash 8 1) returns 16, (ash 8 -1) returns 4

Conditional Keywords

• if
• when
• unless
• cond
• case
• and
• or

Other Keywords

• oddp - return t if odd number, nil if even, errors if not integer
• progn - run a sequence of expressions, returning the last evaluated expression
• y-or-n-p - prompts for a 'y or n' answer `(y-or-n-p "It is Thursday? "), return T for 'y' and Nil for 'n'
• complement - equivalent to "not"
• alphanumericp - returns true for alpha numeric chars, false otherwise
• digit-char-p - returns true if numeric character
• substitute-if [cond] [new item] [list] - generic function can handle multiple datatypes

Reading Keyboard Input

• read - usage: (my_val (read)) - will read numbers, etc. Useful to read structures from files (which have been written by a print statement)
• read-line - usage: (my_val (read-line)) - will only read strings and chars

Printing

• [ ] TODO: confirm how the print statements differ

• print

• prin1
• princ
• princ-to-string
• prin1-to-string - converts any basic lisp type to a string
• write-to-string - writes an expression to a string
• :pretty [t/nil] -> adds new lines or tabs into string

Special Chars

• #\newline
• #\space
• #\tab
• #\backspace
• #\linefeed
• #\page
• #\return
• #\rubout
• #\?
• #\!
• #\.

File Handling

(with-open-file
    (my-stream
    "testfilename.txt"
    :direction :output
    :if-exists :supersede
    )
    (princ "Hello File!" my-strean)
)