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Fixes based on pkh's comments.
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@ -71,16 +71,21 @@ t ; another atom, denoting true.
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;;; Symbols
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'foo ; => FOO
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'foo ; => FOO Notice that the symbol is upper-cased automatically.
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;; Intern manually creates a symbol from a string.
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(intern "AAAA") ; => AAAA
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(intern "aaa") ; => |aaa|
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;;; Numbers
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9999999999999999999999 ; integers
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#b111 ; binary => 7
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#o111 ; octal => 73
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#x111 ; hexadecimal => 273
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3.14159 ; floating point
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3.14159s0 ; single
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3.14159d0 ; double
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1/2 ; ratios
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#C(1 2) ; complex numbers
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@ -104,7 +109,7 @@ t ; another atom, denoting true.
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;;; Booleans
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t ; for true (any not-nil value is true)
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nil ; for false
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nil ; for false - and the empty list
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(not nil) ; => t
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(and 0 t) ; => t
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(or 0 nil) ; => 0
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@ -114,21 +119,21 @@ nil ; for false
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#\λ ; => #\GREEK_SMALL_LETTER_LAMDA
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#\u03BB ; => #\GREEK_SMALL_LETTER_LAMDA
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;;; Strings are fixed-length simple-arrays of characters.
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;;; Strings are fixed-length arrays of characters.
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"Hello, world!"
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"Benjamin \"Bugsy\" Siegel" ; backslash is an escaping character
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;; Strings can be concatenated too!
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(concatenate 'string "Hello " "world!") ; => "Hello world!"
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;; A string can be treated like a list of characters
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;; A string can be treated like a sequence of characters
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(elt "Apple" 0) ; => #\A
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;; format can be used to format strings:
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(format nil "~a can be ~a" "strings" "formatted")
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;; Printing is pretty easy
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(format t "Common Lisp is groovy. Dude.\n")
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;; Printing is pretty easy; ~% is the format specifier for newline.
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(format t "Common Lisp is groovy. Dude.~%")
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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@ -136,15 +141,19 @@ nil ; for false
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; You can create a global (dynamically scoped) using defparameter
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;; a variable name can use any character except: ()[]{}",'`;#|\
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;; Dynamically scoped variables should have earmuffs in their name!
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(defparameter *some-var* 5)
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*some-var* ; => 5
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;; You can also use unicode characters. Not very easy to use though...
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(defparameter *foo#\u03BBooo* nil)
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;; You can also use unicode characters.
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(defparameter *AΛB* nil)
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;; Accessing a previously unassigned variable is an undefined
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;; behavior (but possible). Don't do it.
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;; Accessing a previously unbound variable is an
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;; undefined behavior (but possible). Don't do it.
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;; Local binding: `me` is bound to "dance with you" only within the
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;; (let ...). Let always returns the value of the last `form` in the
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@ -165,9 +174,12 @@ nil ; for false
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:breed "collie"
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:age 5))
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*rover* ; => #S(DOG :NAME "rover" :BREED "collie" :AGE 5)
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(dog-p *rover*) ; => t ;; ewww)
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(dog-name *rover*) ; => "rover"
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;; Dog-p, make-dog, and dog-name are all created by defstruct!
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;;; Pairs
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;; `cons' constructs pairs, `car' and `cdr' extract the first
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;; and second elements
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@ -188,12 +200,16 @@ nil ; for false
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;; Can still use `cons' to add an item to the beginning of a list
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(cons 4 '(1 2 3)) ; => '(4 1 2 3)
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;; Use `append' to add lists together
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;; Use `append' to - surprisingly - append lists together
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(append '(1 2) '(3 4)) ; => '(1 2 3 4)
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;; Lists are a very basic type, so there is a wide variety of functionality for
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;; Or use concatenate -
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(concatenate
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;; Lists are a very central type, so there is a wide variety of functionality for
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;; them, a few examples:
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(mapcar #1+ '(1 2 3)) ; => '(2 3 4)
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(mapcar #'1+ '(1 2 3)) ; => '(2 3 4)
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(mapcar #'+ '(1 2 3) '(10 20 30)) ; => '(11 22 33)
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(remove-if-not #'evenp '(1 2 3 4)) ; => '(2 4)
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(every #'evenp '(1 2 3 4)) ; => nil
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@ -217,60 +233,96 @@ nil ; for false
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(make-array (list 2 2))
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;; (make-array '(2 2)) works as well.
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; => #2A((0 0) (0 0))
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(make-array (list 2 2 2))
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; => #3A(((0 0) (0 0)) ((0 0) (0 0)))
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;; Caution- the default initial values are
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;; implementation-defined. Here's how to define them:
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; access the element at 1,1,1,
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(make-array '(2) :initial-element 'unset)
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; => #(UNSET UNSET)
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;; And, to access the element at 1,1,1 -
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(aref (make-array (list 2 2 2)) 1 1 1)
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; => 0
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;;; Sets are just lists:
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;;; Naively, sets are just lists:
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(set-difference '(1 2 3 4) '(4 5 6 7)) ; => (3 2 1)
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(intersection '(1 2 3 4) '(4 5 6 7)) ; => 4
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(union '(1 2 3 4) '(4 5 6 7)) ; => (3 2 1 4 5 6 7)
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(adjoin 4 '(1 2 3 4)) ; => (1 2 3 4)
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;; But you'll want to use a better data structure than a linked list
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;; for performant work!
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;;; Dictionaries are implemented as hash tables.
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;; Create a hash table
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(defparameter m (hash-table))
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(defparameter *m* (make-hash-table))
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;; set a value
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(setf (gethash 'a hash-table 1))
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(setf (gethash 'a *m*) 1)
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;; Retrieve a value
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(gethash 'a m) ; => 1
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(gethash 'a *m*) ; => 1, t
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;; Retrieving a non-present value returns a nil
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(gethash m 'd) ;=> nil
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;; Detail - Common Lisp has multiple return values possible. gethash
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;; returns t in the second value if anything was found, and nil if
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;; not.
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;; Retrieving a non-present value returns nil
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(gethash *m* 'd) ;=> nil, nil
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;; You can provide a default value for missing keys
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(gethash m 'd :not-found) ; => :NOT-FOUND
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(gethash *m* 'd :not-found) ; => :NOT-FOUND
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;; Let's handle the multiple return values here in code.
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(multiple-value-bind
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(a b)
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(gethash 'd *m*)
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(list a b))
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; => (NIL NIL)
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(multiple-value-bind
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(a b)
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(gethash 'a *m*)
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(list a b))
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; => (1 T)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; 3. Functions
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Use `lambda' to create anonymous functions.
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;; A function always returns the value of its last expression
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(lambda () "Hello World") ; => #<function>
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;; A function always returns the value of its last expression.
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;; The exact printable representation of a function will vary...
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(lambda () "Hello World") ; => #<FUNCTION (LAMBDA ()) {1004E7818B}>
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;; Use funcall to call lambda functions
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(funcall (lambda () "Hello World")) ; => "Hello World"
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;; Or Apply
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(apply (lambda () "Hello World") nil) ; => "Hello World"
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;; De-anonymize the function
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(defun hello-world () "Hello World")
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(defun hello-world ()
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"Hello World")
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(hello-world) ; => "Hello World"
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;; The () in the above is the list of arguments for the function
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(defun hello (name)
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(format nil "Hello, ~a " name))
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(hello "Steve") ; => "Hello, Steve"
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;; Functions can have optional arguments; they default to nil
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@ -286,6 +338,12 @@ nil ; for false
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(defun hello (name &optional (from "The world"))
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(format t "Hello, ~a, from ~a" name from))
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(hello "Steve")
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; => Hello, Steve, from The world
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(hello "Steve" "the alpacas")
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; => Hello, Steve, from the alpacas
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;; And of course, keywords are allowed as well... usually more
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;; flexible than &optional.
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@ -302,18 +360,18 @@ nil ; for false
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;; 4. Equality
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Common Lisp has a sophisticated equality system.
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;; Common Lisp has a sophisticated equality system. A couple are covered yere.
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;; for numbers use `='
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(= 3 3.0) ; => t
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(= 2 1) ; => nil
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;; for object identity (approximately) use `eq?'
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;; for object identity (approximately) use `eql`
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(eql 3 3) ; => t
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(eql 3 3.0) ; => nil
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(eql (list 3) (list 3)) ; => nil
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;; for collections use `equal'
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;; for lists, strings, and bit-vectors use `equal'
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(equal (list 'a 'b) (list 'a 'b)) ; => t
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(equal (list 'a 'b) (list 'b 'a)) ; => nil
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@ -352,7 +410,7 @@ nil ; for false
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;; Of course recursion is supported:
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(defun walker (n)
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(if (= n 0)
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(if (zerop 0)
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:walked
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(walker (1- n))))
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@ -380,8 +438,8 @@ nil ; for false
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;; demonstrated earlier in the hash table example.
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(let ((variable 10))
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(setf variable 10))
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; => 10
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(setf variable 2))
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; => 2
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;; Good Lisp style is to minimize destructive functions and to avoid
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@ -403,6 +461,15 @@ nil ; for false
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:initarg :average-efficiency)
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(:documentation "A human powered conveyance"))
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;; defclass, followed by name, followed by the superclass list,
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;; followed by slot list, followed by optional qualities such as
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;; :documentation.
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;; When no superclass list is set, the empty list defaults to the
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;; standard-object class. This *can* be changed, but not until you
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;; know what you're doing. Look up the Art of the Metaobject Protocol
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;; for more information.
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(defclass bicycle (human-powered-conveyance)
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((wheel-size
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:accessor wheel-size
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@ -424,6 +491,7 @@ nil ; for false
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:accessor number-of-rowers
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:initarg :number-of-rowers)))
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;; Calling DESCRIBE on the human-powered-conveyance class in the REPL gives:
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(describe 'human-powered-conveyance)
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@ -438,7 +506,7 @@ nil ; for false
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; Direct superclasses: STANDARD-OBJECT
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; Direct subclasses: UNICYCLE, BICYCLE, CANOE
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; Not yet finalized.
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; Direct slots:
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(defparameter *foo#\u03BBooo* nil) ; Direct slots:
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; VELOCITY
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; Readers: VELOCITY
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; Writers: (SETF VELOCITY)
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@ -450,10 +518,12 @@ nil ; for false
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;; designed to be an interactive system
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;; To define a method, let's find out what our circumference of the
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;; bike turns out to be using the equation: C = d * pi
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;; bike wheel turns out to be using the equation: C = d * pi
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(defmethod circumference ((object bicycle))
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(* 3.14159 (wheel-size object)))
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(* pi (wheel-size object)))
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;; pi is defined in Lisp already for us!
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;; Let's suppose we find out that the efficiency value of the number
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;; of rowers in a canoe is roughly logarithmic. This should probably be set
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@ -488,7 +558,7 @@ nil ; for false
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`condition` is tested prior to each execution of `body`"
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(let ((block-name (gensym)))
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`(tagbody
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(when (not ,condition)
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(unless ,condition
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(go ,block-name))
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(progn
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,@body)
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@ -503,13 +573,14 @@ nil ; for false
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`condition` is tested prior to each execution of `body`"
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`(loop while ,condition
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do
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,@body))
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(progn
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,@body)))
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;; However, with a modern compiler, this is not required; the LOOP
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;; form compiles equally well and is easier to read.
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;; Note that ` is used, as well as , and @. ` is a quote-type operator
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;; known as quasiquote; it allows the use of ,. , allows "unquoting"
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;; Note that ``` is used, as well as `,` and `@`. ``` is a quote-type operator
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;; known as quasiquote; it allows the use of `,` . `,` allows "unquoting"
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;; variables. @ interpolates lists.
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;; Gensym creates a unique symbol guaranteed to not exist elsewhere in
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@ -529,3 +600,5 @@ nil ; for false
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Lots of thanks to the Scheme people for rolling up a great starting
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point which could be easily moved to Common Lisp.
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- [Paul Khoung](https://github.com/pkhuong) for some great reviewing.
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