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The TeachScheme Project

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Emphasis on correctness over efficiency (ie, focus on program design) ... Make students waste time on unimportant and uninteresting details ... – PowerPoint PPT presentation

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Title: The TeachScheme Project

1
The TeachScheme! Project

Rice University
University of Utah

2
The Revolution

Two principles

Shift away from machine details
Emphasis on correctness over efficiency (ie,
focus on program design)
3
Whats Wrong withMachine-Oriented Languages?
machine arithmetic, pointers and memory
addresses, even i/o

Make students waste time on unimportant and
uninteresting details
Force students to confront issues they are not
prepared for
and ...

4
What Computer Scienceis Not About
The computer! Just as biology isnt
microscope science and writing isnt pen
science ...
5
Whats This AboutProgram Design?
6
Why Am I Here?

The TeachScheme! Project Outreach program at
Rice University
Specially designed for high schools
Provides all teaching material books, software,
etc (free of charge)

7
A Teachers Experience
8
K.I.S.S.Keep It Simple Syntactically

C/Pascal
10 Problem-solving vs 90 Syntax

9
The Golden Rule ofScheme Syntax

Operation
List-of-Arguments
or ( Operation Arg1
)
10
The Golden Rule ofScheme Syntax

Operation
List-of-Arguments
or ( Operation Arg1 Arg2
)
11
The Golden Rule ofScheme Syntax

Operation
List-of-Arguments
or ( Operation Arg1 Arg2 . . . Argn )
12
An Example From Arithmetic

( Operation Arg1 Arg2 )
13
Example 1 (contd)

4 5
( Operation Arg1 Arg2 )
( )

14
Example 1 (contd)

4 5
( Operation Arg1 Arg2 )
( )

15
Example 1 (contd)

4 5
( Operation Arg1 Arg2 )
( 4 )

16
Example 1 (contd)

4 5
( Operation Arg1 Arg2 )
( 4 5 )

17
Example 1 (contd)

4 5
( 4 5 )

18
Another Arithmetic Example

( 4 5 ) 6

19
Example 2 (contd)

( 4 5 ) 6
( )

20
Example 2 (contd)

( 4 5 ) 6
( )

21
Example 2 (contd)

( 4 5 ) 6
( ( 4 5 ) )

22
Example 2 (contd)

( 4 5 ) 6
( ( 4 5 ) 6 )

23
Example 2 (contd)

( 4 5 ) 6
( ( 4 5 ) 6 )

24
An Example From Algebra

f ( x ) x 5
25
Example 3 (contd)

f ( x ) x 5
( Operation Arg1 Arg2 )

26
Example 3 (contd)

f ( x ) x 5
( Operation Arg1 Arg2 )
(
)

27
Example 3 (contd)

f ( x ) x 5
( Operation Arg1 Arg2 )
( define
)

28
Example 3 (contd)

f ( x ) x 5
( Operation Arg1 Arg2 )
( function-name input-name )
( f x )

29
Example 3 (contd)

f ( x ) x 5
( Operation Arg1 Arg2 )
( define ( f x )
)

30
Example 3 (contd)

f ( x ) x 5
( Operation Arg1 Arg2 )
( output-rule )
( x 5 )

31
Example 3 (contd)

f ( x ) x 5
( Operation Arg1 Arg2 )
( define ( f x )
( x 5 ) )

32
Example 3 (contd)

f ( x ) x 5
( define ( f x )
( x 5 ) )

33
Algebra vs Scheme vs Pascal
34
Design
35
D3 Data Drive Design(A Non-Numeric Example)

Consider program guest, which determines
whether a friends name is in a partys
invitation list.

36
Is Mathilde In The List?
No
Yes
Look in the Rest of the List
37
Is Mathilde InThe Rest of the List?
No
Yes
Look in the Rest of the List
38
Pattern To Algebra
39
Algebra
guest ( name, list )
40
Algebra
guest ( name, list )
41
Algebra
guest ( name, list ) if list is empty
42
Algebra
guest ( name, list ) no if list is empty

43
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44
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45
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46
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47
Algebra
guest ( name, list )
Scheme
( define ( guest name list )
)

48
Algebra
guest ( name, list )
Scheme
( define ( guest name list )
)

49
Algebra
guest ( name, list )
50
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51
Scheme
( define ( guest name list ) ( cond
( )
( ) ( )
))
52
Algebra
guest ( name, list ) if list is empty
if name first ( list ) otherwise
Scheme
( define ( guest name list ) ( cond
( ( empty? list )
) ( ( equal? name ( first list ))
) ( else
) ))
53
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54
Did You Notice?
55
Algebra
guest ( name, list ) no if list is empty
yes if name first ( list ) guest ( name,
rest ( list )) otherwise
Scheme
( define ( guest name list ) ( cond
( ( empty? list ) no
) ( ( equal? name ( first list
)) yes ) ( else
( guest name (
rest list )) ) ))
56
Recursion Is Natural
57
Comparisons
58
Pascal
Program NameOnList (Input, Output) Type
ListType NodeType NodeType
Record First
String Rest
ListType End Var
List ListType Name
String Procedure GetList (Var List ListType)
. . . Function Guest (Name String List
ListType) String Begin If List nil
Then Guest no Else If Name
List.First Then Guest yes
Else Guest Guest ( Name, List.Rest)
End Begin Readln ( Name ) GetList (
List ) Writeln (Guest ( Name, List ) ) End
.
59
Pascal
Program NameOnList (Input, Output) Type
ListType NodeType NodeType
Record First
String Rest
ListType End Var
List ListType Name
String Procedure GetList (Var List ListType)
. . . Function Member (Name String List
ListType) String Begin If List nil
Then Member no Else If Name
List.First Then Member yes
Else Member Member ( Name,
List.Rest) End Begin Readln ( Name )
GetList ( List ) Writeln (Member ( Name,
List ) ) End .
60
C or C
include ltstdio.hgt typedef struct listCell
list struct listCell int first list
rest bool guest (int x, list l) if (l
NULL) return false else if (x (l -gt
first)) return true else return guest
(x, l -gt rest) int main (int argc, char
argv) list l1, l2, l3 NULL int x l1
(list) malloc (sizeof (struct listCell)) l2
(list) malloc (sizeof (struct listCell)) l2 -gt
first 3 l2 -gt rest l3 l1 -gt first 2
l1 -gt rest l2 scanf ("d", x) printf
("d\n", member (x, l1))
61
Principles of Program Design