Scheme

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???? ????? ????? ????? ???? Scheme

• ????? 1

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??????? ??????

• ??? ????? (???? ?????? ????, ????? ???? ?????(
• ??? ????? www.cs.tau.ac.il/scheme
• ???????
• ?????
• ????? (????? ???? ?????)

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http//www.cs.tau.ac.il/scheme
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???????

• ??????? ??????? ?????? ????.
• ???? ???????? ??? ?????.
• ??????? ????? ??????? ??? ?? ??????? ???? ????
  (??????? ??? ??????? ????).
• ???? ????? 80 ????????? ??????.
• ???? ?????? ???????? ??? ??? 005 ????? ?????,
  ????? ??????.
• ????? ??, ?.?., ???? ?????, ?????? ????.
• ????? ????? ???? ????? ????? ??????.
• ????? ???? ?????.

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Scheme

• Lisp List Processing
• ?????? (interpreter) ???? ??????? ?-Lisp
• Scheme ??? ?? Lisp
• ????? ?? ????, ????? ?????????? ??? ???????.

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Dr. Scheme ?????

• ????? ?????? (????? 209)
• ????? ????, ??? ??? ?????, ??
• http//www.drscheme.org
• ????? ?????? ?????? ?????? ?????? ????? Linux
• drscheme
• ?????? ??????? (????)
• Language-gtChoose Language-gt
• Graphical (under
  PLT tab)
• (???? ?????? ?? ????? ?? ????? ?-Run)

!
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(No Transcript)
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???? ???????
???? ???????????
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????? ?????
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????? ????? ???????
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??????? ?-Scheme (?????)

• ????? ???? lt,,586
• ?-interpreter ???? ?????? ????? ?????? ?? ??????.
• ?????????
• ( 1 3 5 7)
• ????? ??????? ??? ???????, ??????? ?????????.
• ???????? ????? ????????? prefix notation.

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????? ????? ???????????
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????? ????? ???????
Click on Run
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Nesting

• ????? ?? ?????????? ?????????? ??????????
• ???? ?? ??????????.
• ( ( 100 1)
• ( (- 10 7)
• (/ 24 6)
• )
• (

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???? ????? ?? DrScheme
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??? ?????

• ????? ?-interpreter ????? ???-??????? (????????
  ????????) ??? ????? ?? ???????? ?? ?????????.
• ???? ??? ????? ????????.

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??????? ?-,Scheme ????

• ???? (define x 7)
• ??????? ?????? ?????? ?? ???????????.
• ???? ???? ??????, ???? ????? ??????? ??
• ????????, special form, ????? ??? ???? ???
• ?? ?????? ?? ?????????.
• ????? ?????? ????? ????? ?? ?? ????, ???????
• ???? ??????, environment.

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??????? ?-,Scheme ????

• ????????
• (lambda (x) ( x x))
• ????????? (,) ?? ?????? (square)
• (lambda (parameters ltgt) ltbodygt)
• ?????
• ((lambda (x) ( x x)) 7)

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???? ??????

• ???? ?????? (syntactic sugar), ??? ????? ??????
  ????? ????? ????? ???? ?? ????.
• (define (square x) ( x x))
• (define (name ltparametersgt) ltbodygt)
• (square 7)
• (define (sum-of-squares x y)
• ( (square x) (square y)))
• (sum-of-squares 3 4)

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???? ?????

• ?????? ???-???????, ???????? ????????, ??????
  ???????? ?? ?????????.
• Normal order evaluation
• ???? ????? ???????? ??????? ??? ?????
• ???????? (expand), ??? ????? ??????? (reduce)
• Applicative order evaluation
• ????? ?? ????????? ??? ????? ?? ????????.

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Normal vs. Applicative order
(define (square x) ( x x)) (define
(sum-of-squares x y) ( (square x)
(square y))) (define (foo a) (sum-of-squares ( a
1) ( a 2))) (foo 5)

• Normal order
• (sum-of-squares ( 5 1) ( 5 2))
• ( (square ( 5 1)) (square ( 5 2)))
• ( ( ( 5 1) ( 5 1)) ( ( 5 2) ( 5 2)))
• ( ( 6 6) ( 10 10))
• ( 36 100)
• 136

• Applicative order
• (sum-of-squares ( 5 1) ( 5 2))
• 6 10
• ( (square 6) (square 10))
• ( ( 6 6) ( 10 10))
• ( 36 100)
• 136

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What is the Scheme order?
(define (square x) ( x x)) (define
(sum-of-squares x y) ( (square x)
(square y))) (define (foo a) (sum-of-squares ( a
1) ( a 2))) (foo 5)
With DrScheme stepper
works for Beginning Student Language level only
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special forms, ????

• (if ltpredicategt ltconsequentgt ltalternativegt)
• predicate ?????? ???? ??????? true ?? false.
• ?? ???? ??? true,
• ????? ?? consequent ?????? ?? ????? ???????.
• ????, ????? ?? alternative ?????? ?? ?????
  ???????.

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????? ??? ?????

• (define (abs x)
• (if (lt x 0)
• (- x)
• x))

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??? ?????

• (define (foo a b)
• ((if (gt b 0) -) a b))
• (foo 2 6)
• (foo 5 -4)

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????????? ??????

• (and (lt x 95) (gt x 85))
• ????? ??? ???? ?? ?-false ??????.
• (or (gt x 95) (lt x 85))
• ????? ??? ???? ?? ?-true ??????.
• ??? special-forms, ??? ?? ????? ??????? ??
  ????????.

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?????? ??????

• Scheme ???? ?"?????? ??????", ???? ???????
  ???????? ?????????? ??????????? ???? ????? ??? (
  gt 232-1, gt 264-1)

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?????? ????????? ????????