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Why Won’t Lisp Just Go
      Away?
       Inroducing Lisp
      50 Years Young (2008)
http://lisperati.org/casting.html, by permission of Conrad Barski, MD
Effort vs Productivity
                   (my subjective point of view)
                                 (not to scale)
  ...
Overview
 What is Lisp?
 How to get started
   Some Basics
   Some Common Recipes
 Wet your appetite for more
   Not so ba...
What is Lisp?
 A Programming Language
 Brought to you by John McCarthy circa 1958
 Resistance is Futile...
    Garbage Col...
Welcome to the Family
 Common Lisp (Lisp 2)
    LispWorks, Alegro

    OpenMCL, SBCL, Clisp, ABCL and others

 Scheme (Lis...
Quick Start
LispBox
  http://gigamonkeys.com/lispbox/
  Windows, OS X, Linux

Ready Lisp
  http://www.newartisans.com/soft...
Roll your own
 Emacs
 SLIME
   The Superior Lisp Interaction Mode for Emacs
 Common Lisp
   SBCL, CLISP
 paraedit-el
Basics

 Parentheses, lots and lots of parentheses
 Everything is an Expression
 Prefix Notation
 Lists, ‘cons’, pair
   Si...
Basics: Cons Cells, Lists
car
                          (), nil, the empty list, false
          cdr



 1                ...
Basics: Expressions
(if test-p consequent otherwise)

(+ 1 2 3 4 5)   => 15

(let ((x 3)
      (y 2))
  (* x y))      => 6...
Basics: Functions
(defun test (n)
  (cond
    ((= n 0)
	    (+ 1 n))
	   (t
	    (- n 1))))

(funcall #'test 3)
(apply #’t...
Basics: Assignment
 (setf x '(a b c))
 => (A B C)

 (setf (car x) 1)
 => (1 B C)

 (setf (second x) 2)
 => (1 2 C)
Numeric Tower

 Ints and Floats, but also...
 Ratios
 Built in Bignum Support
 Built in Complex Numbers
Numeric Tower
1/2
(/ 1 3)               => 1/3
(* 33333 (/ 1 33333)) => 1


(expt 2 100)          => 126765060022822940149...
Familiar Data Structures
 Vectors (arrays)
 Hash Tables (map)
 Structures (records)
 Objects - CLOS
 Sequence Types (and s...
Library System: ASDF
 ASDF - another system definition facility
   Like Ruby’s gem or Perl’s CPAN (but inscrutable)
 (requi...
Example: Fetch the Web

(require :drakma)
(use-package :drakma)
(defvar content nil)
(setf content
  (http-request quot;ht...
Example: Serve the Web
(require :hunchentoot)
(use-package :hunchentoot)
(setq *dispatch-table*
  (list
    (create-prefix...
Example: Process Files

(require :cl-ppcre)

(with-open-file (inp quot;.../input.txtquot; :direction :input)
  (loop for l...
Example: Unit Testing
(define-test test-flatten
 (assert-false (flatten))
 (assert-false (flatten '()))
 (assert-equal '(a...
More Interesting Stuff

 Macros, Reader Macros, syntax-rules
 Restarts
   “To Err is Expected, To Recover, Divine” -- Davi...
What’s a Macro?
  A tool for Abstraction
  Code Generator
  Compiler


  defmacro
  define-macro
  syntax-rules
Macro: random-if

(defmacro random-if (prob consequent otherwise)
  `(if (< (random 1.0) ,prob))
       ,consequent
      ...
Macro: aprog1
(defmacro aprog1 (it &rest body)
  `(let ((it ,it))      give the thing   a name
     ,@body
               ...
Macro: rcut
(defmacro rcut (&rest body)
 (let* ((formals (list))
        (new-body
         (map-tree #'(lambda (elt)
    ...
Restarts: Structured Recovery
(defun file-size (file)
  (restart-case
    (if (not (probe-file file))       ‘throw’
      ...
Restarts in action
CL-USER> (format t quot;bytes:~a~&quot; (bytes-used '(quot;/etc/passwdquot; quot;/foo/barquot;)))
Condi...
More Interesting Stuff

 Functional Programming
   Functions are first class - composable
   list comprehensions (cl-incf)
...
First Class Functions
(mapcar #'(lambda (x) (+ 2 x))
          '(1 2 3 4))       => ‘(3 4 5 6)

(defun curry (fn &rest arg...
First Class Functions

 (defun memoize (fn)
   (let ((cache (make-hash-table :test #'equal)))
      #’(lambda (&rest args)...
First Class Functions
(defun myfn (a b c)
  (format t quot;called: a:~a b:~a c:~a~&quot; a b c)
  (+ a b c))

(let ((mfn (...
List Comprehensions
(defun lcmp-qsort (things)
  (cond ((null things)
	 things)
	 (t
	 (destructuring-bind (pivot . tl) th...
List Comprehensions
(defun lcmp-qsort (things)
  (cond ((null things)
	 things)
	 (t
	 (destructuring-bind (pivot . tl) th...
List Comprehensions
(defun lcmp-qsort (things)
  (cond ((null things)
	 things)
	 (t
	 (destructuring-bind (pivot . tl) th...
List Comprehensions
(defun lcmp-qsort (things)
  (cond ((null things)
	 things)
	 (t
	 (destructuring-bind (pivot . tl) th...
List Comprehensions
(defun lcmp-qsort (things)
  (cond ((null things)
	 things)
	 (t
	 (destructuring-bind (pivot . tl) th...
List Comprehensions
(defun lcmp-qsort (things)
  (cond ((null things)
	 things)
	 (t
	 (destructuring-bind (pivot . tl) th...
List Comprehensions

(defun all-permutations (things)
  (cond
    ((= 1 (length things))
     (list things))
    (t
     (...
List Comprehensions

(defun all-permutations (things)
  (cond
    ((= 1 (length things))
     (list things))
    (t
     (...
List Comprehensions

(defun all-permutations (things)
  (cond
    ((= 1 (length things))
     (list things))
    (t
     (...
List Comprehensions

(defun all-permutations (things)
  (cond
    ((= 1 (length things))
     (list things))
    (t
     (...
List Comprehensions

(defun all-permutations (things)
  (cond
    ((= 1 (length things))
     (list things))
    (t
     (...
List Comprehensions

(defun all-permutations (things)
  (cond
    ((= 1 (length things))
     (list things))
    (t
     (...
Pattern Matching: pcond
(defun ptest (names)
  (pcond:pcond
   ((and (:pat ((?first ?last) . ?rest)
	          names)
	   ...
DSLs, mini-languages
(define-syntax aprog1
  (syntax-rules (it)
    ((_ expression . body)
     (let ((it expression))
   ...
DSLs, mini-languages

(define m
  (automation init
    (init : (c -> more))
    (more : (a -> more)
            (d -> more...
DSLs, mini-languages
(define-syntax automation
  (syntax-rules (: ->)
    ((_ init-state
	     (state : (label -> target) ...
DSLs, mini-languages
(letrec
  ((init (lambda (GenTemp%2)
           (cond ((empty? GenTemp%2) #t)
                 (else ...
That’s the overview




 http://lisperati.org/casting.html, by permission of Conrad Barski, MD
Now where am I supposed to go?
 On-Line Resources

   Common Lisp Hyper Spec

   On Lisp (Paul Graham)

   Practical Commo...
Now where am I supposed to go?

 Books
  PAIP (Peter Norvig)
  Practical Common Lisp (Peter Seibel)
  SICP (Ableson and Su...
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Introduction To Lisp

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Introduction to Lisp. A survey of lisp's history, current incarnations and advanced features such as list comprehensions, macros and domain-specific-language [DSL] support.

Published in: Technology

Introduction To Lisp

  1. 1. Why Won’t Lisp Just Go Away? Inroducing Lisp 50 Years Young (2008)
  2. 2. http://lisperati.org/casting.html, by permission of Conrad Barski, MD
  3. 3. Effort vs Productivity (my subjective point of view) (not to scale) (this chart has no meaning, it is a joke) 100 PAIP, On Lisp, SICP 75 The segafault that made you leave C++ 50 Java Cookbook EJB3, J5EE, JMX, Me Struts, JMS, Exhausted Permgen 25 You are Here 0 Java C++ Lisp
  4. 4. Overview What is Lisp? How to get started Some Basics Some Common Recipes Wet your appetite for more Not so basic things Where to go next
  5. 5. What is Lisp? A Programming Language Brought to you by John McCarthy circa 1958 Resistance is Futile... Garbage Collection, Closures, Functional, Object Oriented, AOP, DSLs, Conditions and Restarts, Continuations, what else ya got?
  6. 6. Welcome to the Family Common Lisp (Lisp 2) LispWorks, Alegro OpenMCL, SBCL, Clisp, ABCL and others Scheme (Lisp 1) by Sussman and Steele PLT, Chicken, Bigloo, Clojure, SISC, JScheme, and others Less Common Dylan, Qi, Termite, ECL, Arc, and others...
  7. 7. Quick Start LispBox http://gigamonkeys.com/lispbox/ Windows, OS X, Linux Ready Lisp http://www.newartisans.com/software/readylisp.html OS X
  8. 8. Roll your own Emacs SLIME The Superior Lisp Interaction Mode for Emacs Common Lisp SBCL, CLISP paraedit-el
  9. 9. Basics Parentheses, lots and lots of parentheses Everything is an Expression Prefix Notation Lists, ‘cons’, pair Singly Linked List
  10. 10. Basics: Cons Cells, Lists car (), nil, the empty list, false cdr 1 (list 1) (cons 1 nil) 1 2 (cons 1 2) 1 2 3 (list 1 2 3) (cons 1 (cons 2 (cons 3 nil)))
  11. 11. Basics: Expressions (if test-p consequent otherwise) (+ 1 2 3 4 5) => 15 (let ((x 3) (y 2)) (* x y)) => 6 (expt 2 42) => 4398046511104
  12. 12. Basics: Functions (defun test (n) (cond ((= n 0) (+ 1 n)) (t (- n 1)))) (funcall #'test 3) (apply #’test ‘(3)) (mapcar #'test '(-2 -1 0 1 2)) => (-3 -2 1 0 1)
  13. 13. Basics: Assignment (setf x '(a b c)) => (A B C) (setf (car x) 1) => (1 B C) (setf (second x) 2) => (1 2 C)
  14. 14. Numeric Tower Ints and Floats, but also... Ratios Built in Bignum Support Built in Complex Numbers
  15. 15. Numeric Tower 1/2 (/ 1 3) => 1/3 (* 33333 (/ 1 33333)) => 1 (expt 2 100) => 1267650600228229401496703205376 (* #c(0 1) #c(0 1)) => -1
  16. 16. Familiar Data Structures Vectors (arrays) Hash Tables (map) Structures (records) Objects - CLOS Sequence Types (and streams)
  17. 17. Library System: ASDF ASDF - another system definition facility Like Ruby’s gem or Perl’s CPAN (but inscrutable) (require :asdf-install) (asdf-install:install :cl-ppcre) Repository: cliki.net
  18. 18. Example: Fetch the Web (require :drakma) (use-package :drakma) (defvar content nil) (setf content (http-request quot;http://google.com/quot;)) (format t quot;len:~a~&quot; (length content)) (format t quot;~a~&quot; (subseq content 0 100))
  19. 19. Example: Serve the Web (require :hunchentoot) (use-package :hunchentoot) (setq *dispatch-table* (list (create-prefix-dispatcher quot;/indexquot; 'index-page))) (defun index-page () quot;<h1>Hunchentoot Demo</h1>.quot;) (defvar server (hunchentoot:start-server :port 4242))
  20. 20. Example: Process Files (require :cl-ppcre) (with-open-file (inp quot;.../input.txtquot; :direction :input) (loop for line = (read-line inp nil nil) while line do (format t quot;~a~&quot; (cl-ppcre:regex-replace quot;lis+pquot; line quot;lispquot;))))
  21. 21. Example: Unit Testing (define-test test-flatten (assert-false (flatten)) (assert-false (flatten '())) (assert-equal '(a) (flatten 'a)) (assert-equal '(a) (flatten '(a))) (assert-equal '(a b c d) (flatten '(a (b (c (d)))))))
  22. 22. More Interesting Stuff Macros, Reader Macros, syntax-rules Restarts “To Err is Expected, To Recover, Divine” -- David B. Lamkins Functional Programming Pattern Matching (Unification)
  23. 23. What’s a Macro? A tool for Abstraction Code Generator Compiler defmacro define-macro syntax-rules
  24. 24. Macro: random-if (defmacro random-if (prob consequent otherwise) `(if (< (random 1.0) ,prob)) ,consequent ,otherwise)) (random-if 1/2 (format t quot;went left~&quot;) (format t quot;went right~&quot;)
  25. 25. Macro: aprog1 (defmacro aprog1 (it &rest body) `(let ((it ,it)) give the thing a name ,@body let them use it it)) return it (aprog1 (make-hash-table :test #’equal) (setf (gethash “a” it) 1) (setf (gethash “b” it) 2)) => #<HASH-TABLE :TEST EQUAL :COUNT 2 {BE49831}>
  26. 26. Macro: rcut (defmacro rcut (&rest body)  (let* ((formals (list))         (new-body          (map-tree #'(lambda (elt)                        (if (symbol-equal '<> elt)                            (aprog1                             (gensym)                             (push it formals)                             it)                            elt))                    body)))    `#'(lambda ,(reverse formals)         ,@new-body))) (macroexpan-1 ‘(rcut (format “val:~a~&” <>))) => #'(LAMBDA (#:G2348) (FORMAT NIL quot;elt:~a~&quot; #:G2348))
  27. 27. Restarts: Structured Recovery (defun file-size (file) (restart-case (if (not (probe-file file)) ‘throw’ (error 'file-not-found) (sb-posix:stat-size (sb-posix:stat file))) (file-not-found (new-file-size) :report quot;Specify missing size.quot; recovery :interactive read-new-value new-file-size))) (defun bytes-used (files) (loop for file in files summing (file-size file)))
  28. 28. Restarts in action CL-USER> (format t quot;bytes:~a~&quot; (bytes-used '(quot;/etc/passwdquot; quot;/foo/barquot;))) Condition FILE-NOT-FOUND was signalled. [Condition of type FILE-NOT-FOUND] Restarts: 0: [FILE-NOT-FOUND] Specify missing size. 1: [ABORT] Return to SLIME's top level. 2: [TERMINATE-THREAD] Terminate this thread (#<THREAD quot;repl-threadquot; ...>) Backtrace: 0: (FILE-SIZE quot;/foo/barquot;) 1: (BYTES-USED (quot;/etc/passwdquot; quot;/foo/barquot;)) ...snip... Enter a new value: 12 bytes:2900
  29. 29. More Interesting Stuff Functional Programming Functions are first class - composable list comprehensions (cl-incf) pattern-matching (cl-unification, pcond) DSLs, mini-languages
  30. 30. First Class Functions (mapcar #'(lambda (x) (+ 2 x)) '(1 2 3 4)) => ‘(3 4 5 6) (defun curry (fn &rest args) #'(lambda (&rest rest) (apply fn (append args rest)))) (funcall (curry #'+ 2) 3) => 5 (mapcar (curry #'+ 2) '(1 2 3 4)) => ‘(3 4 5 6)
  31. 31. First Class Functions (defun memoize (fn) (let ((cache (make-hash-table :test #'equal))) #’(lambda (&rest args) (let ((key (format nil quot;~aquot; args))) (if (gethash key cache) Return (gethash key cache) from cache (aprog1 (apply fn args) (setf (gethash key cache) it))))))) Add result to cache and return
  32. 32. First Class Functions (defun myfn (a b c) (format t quot;called: a:~a b:~a c:~a~&quot; a b c) (+ a b c)) (let ((mfn (memoize #'myfn)) (args '(1 2 3)) (args2 '(4 5 6))) (format t quot;mfn ~a: ~a~&quot; args (apply mfn args)) (format t quot;mfn ~a: ~a~&quot; args (apply mfn args)) (format t quot;mfn ~a: ~a~&quot; args2 (apply mfn args2)) (format t quot;mfn ~a: ~a~&quot; args2 (apply mfn args2))) => called: a:1 b:2 c:3 not in cache mfn (1 2 3): 6 mfn (1 2 3): 6 in cache called: a:4 b:5 c:6 not in cache mfn (4 5 6): 15 mfn (4 5 6): 15 in cache
  33. 33. List Comprehensions (defun lcmp-qsort (things) (cond ((null things) things) (t (destructuring-bind (pivot . tl) things (append (lcmp-qsort (assemble x (<- x tl) (< x pivot))) (list pivot) (lcmp-qsort (assemble x (<- x tl) (>= x pivot))))))))
  34. 34. List Comprehensions (defun lcmp-qsort (things) (cond ((null things) things) (t (destructuring-bind (pivot . tl) things (append (lcmp-qsort (assemble x (<- x tl) (< x pivot))) (list pivot) (lcmp-qsort (assemble x (<- x tl) (>= x pivot))))))))
  35. 35. List Comprehensions (defun lcmp-qsort (things) (cond ((null things) things) (t (destructuring-bind (pivot . tl) things (append (lcmp-qsort (assemble x (<- x tl) (< x pivot))) (list pivot) (lcmp-qsort (assemble x (<- x tl) (>= x pivot))))))))
  36. 36. List Comprehensions (defun lcmp-qsort (things) (cond ((null things) things) (t (destructuring-bind (pivot . tl) things (append (lcmp-qsort (assemble x (<- x tl) (< x pivot))) (list pivot) (lcmp-qsort (assemble x (<- x tl) (>= x pivot))))))))
  37. 37. List Comprehensions (defun lcmp-qsort (things) (cond ((null things) things) (t (destructuring-bind (pivot . tl) things (append (lcmp-qsort (assemble x (<- x tl) (< x pivot))) (list pivot) (lcmp-qsort (assemble x (<- x tl) (>= x pivot))))))))
  38. 38. List Comprehensions (defun lcmp-qsort (things) (cond ((null things) things) (t (destructuring-bind (pivot . tl) things (append (lcmp-qsort (assemble x (<- x tl) (< x pivot))) (list pivot) (lcmp-qsort (assemble x (<- x tl) (>= x pivot))))))))
  39. 39. List Comprehensions (defun all-permutations (things) (cond ((= 1 (length things)) (list things)) (t (assemble (cons Head Tail) (<- Head things) (<- Tail (all-permutations (remove Head things)))))))
  40. 40. List Comprehensions (defun all-permutations (things) (cond ((= 1 (length things)) (list things)) (t (assemble (cons Head Tail) (<- Head things) (<- Tail (all-permutations (remove Head things)))))))
  41. 41. List Comprehensions (defun all-permutations (things) (cond ((= 1 (length things)) (list things)) (t (assemble (cons Head Tail) (<- Head things) (<- Tail (all-permutations (remove Head things)))))))
  42. 42. List Comprehensions (defun all-permutations (things) (cond ((= 1 (length things)) (list things)) (t (assemble (cons Head Tail) (<- Head things) (<- Tail (all-permutations (remove Head things)))))))
  43. 43. List Comprehensions (defun all-permutations (things) (cond ((= 1 (length things)) (list things)) (t (assemble (cons Head Tail) (<- Head things) (<- Tail (all-permutations (remove Head things)))))))
  44. 44. List Comprehensions (defun all-permutations (things) (cond ((= 1 (length things)) (list things)) (t (assemble (cons Head Tail) (<- Head things) (<- Tail (all-permutations (remove Head things)))))))
  45. 45. Pattern Matching: pcond (defun ptest (names) (pcond:pcond ((and (:pat ((?first ?last) . ?rest) names) (:re quot;(.+)oquot; ?first (before-o))) (format t quot;before-o: ~a~&quot; before-o) (ptest ?rest)))) (ptest '((quot;George quot; quot;Washingtonquot;) (quot;Johnquot; quot;Adamsquot;))) => before-o: Ge => before-o: J
  46. 46. DSLs, mini-languages (define-syntax aprog1 (syntax-rules (it) ((_ expression . body) (let ((it expression)) body it)))) (macroexpand '(aprog1 (list) (set! it (cons ‘a it)))) => (let ((it (list))) (set! it (cons 'a it)) it)
  47. 47. DSLs, mini-languages (define m (automation init (init : (c -> more)) (more : (a -> more) (d -> more) (r -> end)) (end :)))
  48. 48. DSLs, mini-languages (define-syntax automation (syntax-rules (: ->) ((_ init-state (state : (label -> target) ...) ...) (letrec ((state (lambda (stream) (cond ((empty? stream) #t) (else (case (first stream) ((label) (target (rest stream))) ... (else #f)))))) ...) init-state))))
  49. 49. DSLs, mini-languages (letrec ((init (lambda (GenTemp%2) (cond ((empty? GenTemp%2) #t) (else (case (first GenTemp%2) ((c) (more (rest GenTemp%2))) (else #f)))))) (more (lambda (GenTemp%2) (cond ((empty? GenTemp%2) #t) (else (case (first GenTemp%2) ((a) (more (rest GenTemp%2))) ((d) (more (rest GenTemp%2))) ((r) (end (rest GenTemp%2))) (else #f)))))) (end (lambda (GenTemp%2) (cond ((empty? GenTemp%2) #t) (else (case (first GenTemp%2) (else #f))))))) init)
  50. 50. That’s the overview http://lisperati.org/casting.html, by permission of Conrad Barski, MD
  51. 51. Now where am I supposed to go? On-Line Resources Common Lisp Hyper Spec On Lisp (Paul Graham) Practical Common Lisp (Peter Siebel) Cliki.net common-lisp.net JRMs Syntax Rules Primer Casting Spells with Lisp: http://lisperati.org/casting.html http://del.icio.us/mortis/lisp
  52. 52. Now where am I supposed to go? Books PAIP (Peter Norvig) Practical Common Lisp (Peter Seibel) SICP (Ableson and Sussman) Common Lisp the Language (Guy Steele) ANSI Common Lisp (Paul Graham)

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