1
Towards MoreNatural Functional Programming Languages
Towards MoreNatural Functional Programming Languages
Brad A. MyersBrad A. MyersHuman-Computer Interaction InstituteHuman-Computer Interaction InstituteSchool of Computer ScienceSchool of Computer ScienceCarnegie Mellon UniversityCarnegie Mellon University
http://www.cs.cmu.edu/~bamhttp://www.cs.cmu.edu/[email protected]@cs.cmu.edu
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 2ICFP’02ICFP’02
The User Interface of Programming Languages
Programming is a human activity Want to improve the ability of people to program It makes sense to look at the human side
Programming is a human activity Want to improve the ability of people to program It makes sense to look at the human side
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 3ICFP’02ICFP’02
— Allen Newell and Stuart Card, 1985— Allen Newell and Stuart Card, 1985
“Millions for compilers but hardly a penny for understanding human programming language use. Now, programming languages are obviously symmetrical, the computer on one side, the programmer on the other. In an appropriate science of computer languages, one would expect that half the effort would be on the computer side, understanding how to translate the languages into executable form, and half on the human side, understanding how to design languages that are easy or productive to use.... The human and computer parts of programming languages have developed in radical asymmetry.”
“Millions for compilers but hardly a penny for understanding human programming language use. Now, programming languages are obviously symmetrical, the computer on one side, the programmer on the other. In an appropriate science of computer languages, one would expect that half the effort would be on the computer side, understanding how to translate the languages into executable form, and half on the human side, understanding how to design languages that are easy or productive to use.... The human and computer parts of programming languages have developed in radical asymmetry.”
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 4ICFP’02ICFP’02
What is “Usability”?
Usability = “The effectiveness, efficiency, and satisfaction with which users can achieve tasks in a particular environment of a product.”
Components: Learnability: Easy to learn so users can get started
rapidly. Effectiveness: Experts can use it effectively and with
high productivity. Low Error rate: Users make few errors. Satisfaction: Pleasant to use. No frustrations for users.
Similar to motivations for functional languages
Usability = “The effectiveness, efficiency, and satisfaction with which users can achieve tasks in a particular environment of a product.”
Components: Learnability: Easy to learn so users can get started
rapidly. Effectiveness: Experts can use it effectively and with
high productivity. Low Error rate: Users make few errors. Satisfaction: Pleasant to use. No frustrations for users.
Similar to motivations for functional languages
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 5ICFP’02ICFP’02
Why Human Computer Interaction?
The field of Human Computer Interaction studies how to improve and evaluate usability
Data, knowledge that can guide designs To make systems more usable
Techniques for evaluating usability So claims can be substantiated So improvements can be made
The field of Human Computer Interaction studies how to improve and evaluate usability
Data, knowledge that can guide designs To make systems more usable
Techniques for evaluating usability So claims can be substantiated So improvements can be made
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 6ICFP’02ICFP’02
Who are the Programmers?
• Not just professional programmers anymore By 2005, 55 million end-user programmers
Compared to only 2.75 million professional programmers
• Not just professional programmers anymore By 2005, 55 million end-user programmers
Compared to only 2.75 million professional programmers
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 7ICFP’02ICFP’02
Design of New Languages
How make design decisions? Based on math, logic, type theory Designer’s intuition or sense of aesthetics Similarity to other languages
But many have known problems
Key concept: If you care about usability:
Can leverage off of what is known andwhat can be learned about people
to guide design decisions
How make design decisions? Based on math, logic, type theory Designer’s intuition or sense of aesthetics Similarity to other languages
But many have known problems
Key concept: If you care about usability:
Can leverage off of what is known andwhat can be learned about people
to guide design decisions
8
What we are doing...
Studying the People
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 9ICFP’02ICFP’02
if ((isMan x) && (isWoman x)) then (raise_hands x) else ()if ((isMan x) && (isWoman x)) then (raise_hands x) else ()
( ) ( )
Research shows that these differences between natural languages and computer languages hurt understanding
Research shows that these differences between natural languages and computer languages hurt understanding
Examples of Problems
The men and women here raise your hands!The men and women here raise your hands!
Buy a paint that is not red or blueBuy a paint that is not red or blueif (( not isRed || isBlue ) x) then buy x else ()if (( not isRed || isBlue ) x) then buy x else () ( ) ( )
(This issue with “and” applies to other natural languages as well.)
(This issue with “and” applies to other natural languages as well.)
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 10ICFP’02ICFP’02
My Research Goals
Make programming significantly easier to learn and more effective for non-professional programmers and beginners
Try to provide a more objective basis for usability decisions for programming language design Apply results of Empirical Studies of Programmers,
Psychology of Programming, and Human-Computer Interaction to programming language design
New studies
Design new programming languages and environments based on these results
Make programming significantly easier to learn and more effective for non-professional programmers and beginners
Try to provide a more objective basis for usability decisions for programming language design Apply results of Empirical Studies of Programmers,
Psychology of Programming, and Human-Computer Interaction to programming language design
New studies
Design new programming languages and environments based on these results
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 11ICFP’02ICFP’02
Multiple Criteria
Focusing on learnability and naturalness for beginners
Less emphasis: Scalability Provability Efficiency Mathematical or Logic properties Similarity to other familiar languages etc.
Focusing on learnability and naturalness for beginners
Less emphasis: Scalability Provability Efficiency Mathematical or Logic properties Similarity to other familiar languages etc.
Gentle Slope Systems
Difficultyof
Use
Program Complexity and Sophistication
Gentle Slope Systems
Difficultyof
Use
Programming in C++
MFC
Program Complexity and Sophistication
Gentle Slope Systems
Difficultyof
Use
Programming in C++
MFC
Program Complexity and Sophistication
FunctionalLanguages?
UI libraries
Gentle Slope Systems
Difficultyof
Use
Programming in C++
MFC
Program Complexity and Sophistication
FunctionalLanguages?
UI libraries
Visual Basic
Basic
C++ Programming
Gentle Slope Systems
Difficultyof
Use
Programming in C++
MFC
Program Complexity and Sophistication
FunctionalLanguages?
UI libraries
Visual Basic
Basic
C Programming
My Goal
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 17ICFP’02ICFP’02
What is “Natural Programming”?
Attempt to make programming closer to the way people think Make programming “more natural”
First, have to find out how people think about algorithms, data structures, etc.
Note: Not “natural language” Still creating a formal language
Attempt to make programming closer to the way people think Make programming “more natural”
First, have to find out how people think about algorithms, data structures, etc.
Note: Not “natural language” Still creating a formal language
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 18ICFP’02ICFP’02
Why Might Being Natural be Good?
“Programming is the process of transforming a mental plan into one that is compatible with the computer.” — Jean-Michel Hoc
So process might be easier if transformation is smaller
Closeness of mapping "The closer the programming world is to the problem
world, the easier the problem-solving ought to be.… Conventional textual languages are a long way from that goal." — Green and Petre
“Programming is the process of transforming a mental plan into one that is compatible with the computer.” — Jean-Michel Hoc
So process might be easier if transformation is smaller
Closeness of mapping "The closer the programming world is to the problem
world, the easier the problem-solving ought to be.… Conventional textual languages are a long way from that goal." — Green and Petre
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 19ICFP’02ICFP’02
Why Might Being Natural be Good?
Example: Inserting item into 3rd place of high score list Conventional Languages:
Loop, starting at end of array, shuffle items down, then insert
Example: Inserting item into 3rd place of high score list Conventional Languages:
Loop, starting at end of array, shuffle items down, then insert
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 20ICFP’02ICFP’02
Why Might Being Natural be Good?
Directness (as in “Direct Manipulation”) “Distance between one's goals and the actions required
by the system to achieve those goals.”— Hutchins, Hollan and Norman
Directness (as in “Direct Manipulation”) “Distance between one's goals and the actions required
by the system to achieve those goals.”— Hutchins, Hollan and Norman
Example: Example:
vs.
VB: Let Shape1.FillColor = &H00FF00FF&
ML: SetColor ( Shape1, 0x00FF00FF )
vs.
VB: Let Shape1.FillColor = &H00FF00FF&
ML: SetColor ( Shape1, 0x00FF00FF )
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 21ICFP’02ICFP’02
Background Research
Empirical Studies of Programmers, Psychology of Programming, and HCI results not being used in the design of new languages 30 years of research on what makes languages hard to
learn and error-prone Java / C# looping, etc.
Summarized in our comprehensive tech report— John Pane and Brad Myers, “Usability Issues in the Design of
Novice Programming Systems” TR# CMU-CS-96-132. Aug, 1996.http://www.cs.cmu.edu/~pane/cmu-cs-96-132.html
Empirical Studies of Programmers, Psychology of Programming, and HCI results not being used in the design of new languages 30 years of research on what makes languages hard to
learn and error-prone Java / C# looping, etc.
Summarized in our comprehensive tech report— John Pane and Brad Myers, “Usability Issues in the Design of
Novice Programming Systems” TR# CMU-CS-96-132. Aug, 1996.http://www.cs.cmu.edu/~pane/cmu-cs-96-132.html
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 22ICFP’02ICFP’02
Examples of Problems Identified
Promote Locality and Avoid Hidden Dependencies Type definitions often are far from the use
Code readability is of key importance Don’t try to reduce keystrokes if makes less readable
Inheritance and object-oriented design are very difficult
Beware of misleading appearances When novices and experts mis-read code Avoid subtle distinctions in syntax E.g., a=b vs. a==b; () vs. [] vs. {}; >= vs. => vs. ->
Promote Locality and Avoid Hidden Dependencies Type definitions often are far from the use
Code readability is of key importance Don’t try to reduce keystrokes if makes less readable
Inheritance and object-oriented design are very difficult
Beware of misleading appearances When novices and experts mis-read code Avoid subtle distinctions in syntax E.g., a=b vs. a==b; () vs. [] vs. {}; >= vs. => vs. ->
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 23ICFP’02ICFP’02
More Examples
People expect consistency with external representations and usage (math, English, etc.): People will search for an analogue in their experience that
is similar to the syntax “and”; a=a+1; a=2 vs. 2=a; 1<a<10; ML: ~ is unary negative, - for subtraction: 5 - ~2 So, if different meaning, should have different presentation
Significant difficulties in finding bugs due to invisible data, dependencies, and control flow
People expect consistency with external representations and usage (math, English, etc.): People will search for an analogue in their experience that
is similar to the syntax “and”; a=a+1; a=2 vs. 2=a; 1<a<10; ML: ~ is unary negative, - for subtraction: 5 - ~2 So, if different meaning, should have different presentation
Significant difficulties in finding bugs due to invisible data, dependencies, and control flow
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 24ICFP’02ICFP’02
HCI Methods for Analyzing Languages
Analyze languages as user interfaces Green’s Cognitive Dimensions
— Green and Petre, 1996, “Usability Analysis of VP Environments: A ‘Cognitive Dimensions Framework’. Journal of VL&C, 7(2): 131-174
13 dimensions
Nielsen’s heuristic analysis principles— Nielsen, J., Usability Engineering. 1993, Boston: Academic
Press 10 principles
Can also perform usability studies for specific issues
Analyze languages as user interfaces Green’s Cognitive Dimensions
— Green and Petre, 1996, “Usability Analysis of VP Environments: A ‘Cognitive Dimensions Framework’. Journal of VL&C, 7(2): 131-174
13 dimensions
Nielsen’s heuristic analysis principles— Nielsen, J., Usability Engineering. 1993, Boston: Academic
Press 10 principles
Can also perform usability studies for specific issues
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 25ICFP’02ICFP’02
Consistency Both a Cognitive Dimension and a Heuristic
Analysis principle C++ uses the word "static" to mean at least 3
different things In C++, can use int a,b; to define globals or locals,
but not as procedure parameters Should be able to copy code and use the same code
elsewhere In Visual Basic, to assign something you use “=”
unless is an object, in which case you use “Set” and “=” "foo = 15" vs. "Set foo = object“
ML: “fun f x = 0” vs. “case e of x => 0”
Both a Cognitive Dimension and a Heuristic Analysis principle C++ uses the word "static" to mean at least 3
different things In C++, can use int a,b; to define globals or locals,
but not as procedure parameters Should be able to copy code and use the same code
elsewhere In Visual Basic, to assign something you use “=”
unless is an object, in which case you use “Set” and “=” "foo = 15" vs. "Set foo = object“
ML: “fun f x = 0” vs. “case e of x => 0”
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 26ICFP’02ICFP’02
Error-Proneness
HCI Principle = Prevent errors C and C++ array bounds errors Requiring the "break" in each branch of C, C++ switch
statements causes many errors (still in Java, fixed in C#) Small typos can result in compilable programs that
perform incorrectly, e.g., "=" for "==” or"x-=3” vs. "x=-3“ orfun f(SOME _)=... (a constructor pattern) vs.fun f(SOME_)=... (a variable)
HCI Principle = Prevent errors C and C++ array bounds errors Requiring the "break" in each branch of C, C++ switch
statements causes many errors (still in Java, fixed in C#) Small typos can result in compilable programs that
perform incorrectly, e.g., "=" for "==” or"x-=3” vs. "x=-3“ orfun f(SOME _)=... (a constructor pattern) vs.fun f(SOME_)=... (a variable)
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 27ICFP’02ICFP’02
Good Error Messages
Should be: clear, helpful, precise, constructive Not “syntax error” In C++, so much flexibility, compiler often doesn’t
know where error is Similar problems with type inference systems
SML/NJ:stdIn:30.1-30.4 Error: operator and operand don't agree [tycon mismatch]
operator domain: ?.t
operand: ?.t
in expression:
f B
Should be: clear, helpful, precise, constructive Not “syntax error” In C++, so much flexibility, compiler often doesn’t
know where error is Similar problems with type inference systems
SML/NJ:stdIn:30.1-30.4 Error: operator and operand don't agree [tycon mismatch]
operator domain: ?.t
operand: ?.t
in expression:
f B
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 28ICFP’02ICFP’02
Closeness of Mapping
HCI principle = Speak the User's Language Expressions of algorithms close to the way users
think of them Also, syntactic Issues:
C++ uses "void" to mean "none", "char" to mean 8-bit number, ...
Visual Basic uses "Dim" to declare variables and "wend" to end while loops
Arrays start at 0 whereas people think of counting from 1 Case sensitivity
HCI principle = Speak the User's Language Expressions of algorithms close to the way users
think of them Also, syntactic Issues:
C++ uses "void" to mean "none", "char" to mean 8-bit number, ...
Visual Basic uses "Dim" to declare variables and "wend" to end while loops
Arrays start at 0 whereas people think of counting from 1 Case sensitivity
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 29ICFP’02ICFP’02
Viscosity
Resistance to local change To change parameters of a function in C++, have to edit
.h file and .cpp file, plus all call sites Changing an “if” statement into a “do” statement was
difficult in early structure editors VLs are very difficult due to layout issues
May have to reposition all lines and boxes to make room and neaten resulting drawing
May need to disconnect and reconnect many wires Need for correct indenting may make Haskell programs
resistant to editing But good editor can help
Resistance to local change To change parameters of a function in C++, have to edit
.h file and .cpp file, plus all call sites Changing an “if” statement into a “do” statement was
difficult in early structure editors VLs are very difficult due to layout issues
May have to reposition all lines and boxes to make room and neaten resulting drawing
May need to disconnect and reconnect many wires Need for correct indenting may make Haskell programs
resistant to editing But good editor can help
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 30ICFP’02ICFP’02
Less is More
HCI principle (“keep it simple”) C, C++ have 16 levels of precedence that have to be
memorized, some of which are left-associative and some are right-associative. Consider:
a=b+=c=+d*e+++f==gwhich is a legal statement in C++ and C
Deep nesting in functional languages “Too many parentheses”
HCI principle (“keep it simple”) C, C++ have 16 levels of precedence that have to be
memorized, some of which are left-associative and some are right-associative. Consider:
a=b+=c=+d*e+++f==gwhich is a legal statement in C++ and C
Deep nesting in functional languages “Too many parentheses”
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 31ICFP’02ICFP’02
Help the user get started with the system
Small things should be simple Programs that do small things must still
often be very large, e.g., creating awindow containing a single red rectangle
The 2-pages needed in Motif to do “Hello World” “zero” lines in Visual Basic
In Java, it still requires: class HelloWorldApp { public static void main(String[] args) { System.out.println("Hello World!");
} }
Note 3 kinds of parentheses, 9 special words ML: print "Hello World!"
Small things should be simple Programs that do small things must still
often be very large, e.g., creating awindow containing a single red rectangle
The 2-pages needed in Motif to do “Hello World” “zero” lines in Visual Basic
In Java, it still requires: class HelloWorldApp { public static void main(String[] args) { System.out.println("Hello World!");
} }
Note 3 kinds of parentheses, 9 special words ML: print "Hello World!"
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 32ICFP’02ICFP’02
Other Issues
Many more, see:http://www.cs.cmu.edu/~NatProg/langeval.html
You can send me examples from each other’s systems!
But these are mainly good for analysis Given a design question, how answer it?
Many more, see:http://www.cs.cmu.edu/~NatProg/langeval.html
You can send me examples from each other’s systems!
But these are mainly good for analysis Given a design question, how answer it?
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 33ICFP’02ICFP’02
Our Research
Lots of gaps in prior research on people and programming
Develop knowledge that can be used in design Ph.D. thesis of John Pane
Available at:
http://www.cs.cmu.edu/~pane/thesis/ Evaluate:
How people express algorithms and think about tasks Vocabulary and notations used
Related to the HCI principles of “know the user”, “task analysis”, and “closeness of mapping”
Lots of gaps in prior research on people and programming
Develop knowledge that can be used in design Ph.D. thesis of John Pane
Available at:
http://www.cs.cmu.edu/~pane/thesis/ Evaluate:
How people express algorithms and think about tasks Vocabulary and notations used
Related to the HCI principles of “know the user”, “task analysis”, and “closeness of mapping”
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 34ICFP’02ICFP’02
Our Studies so far
How people naturally express programming concepts and algorithms1) Nine scenes from PacMan
2) Transforming and calculating data in a spreadsheet
Specific issues of language design3) Selecting specific objects from a group (“and”, “or”, “not”)
How people naturally express programming concepts and algorithms1) Nine scenes from PacMan
2) Transforming and calculating data in a spreadsheet
Specific issues of language design3) Selecting specific objects from a group (“and”, “or”, “not”)
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 35ICFP’02ICFP’02
Experimental Design
Question should not bias the answer So use pictures instead of textual descriptions Concentrate on kids, non-programmers
Subjects should not be “tainted” by existing programming languages
Tested that the results generalize to adults and programmers
Question should not bias the answer So use pictures instead of textual descriptions Concentrate on kids, non-programmers
Subjects should not be “tainted” by existing programming languages
Tested that the results generalize to adults and programmers
Usually Pacman moves like this.
Now let's say we add a wall.
Pacman moves like this.
Not like this.
Usually Pacman moves like this.
Now let's say we add a wall.
Pacman moves like this.
Not like this.
Do this: Write a statement that summarizes how I (as the computer) should move Pacman in relation to the presence or absence of other things.
Study 1
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 37ICFP’02ICFP’02
Second Study
Whether similar results from other domains and with adults
Developed 11 questions with scenarios using spreadsheets To test database access and operations More conventionally “computational”
Whether similar results from other domains and with adults
Developed 11 questions with scenarios using spreadsheets To test database access and operations More conventionally “computational”
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 38ICFP’02ICFP’02
Example Question, 2nd Study
No.
Firstname
Lastname
Group
1 Sandra Bullock 2 Bill Clinton 3 Cindy Crawford 4 Tom Cruise 5 Bill Gates 6 Whitney Houston 7 Michael Jordan 8 Jay Leno 9 David Letterman 10 Will Smith
Question 4• Describe in detailed steps what the computer should do to
categorize these people into 2 groups of ‘Gold’ and ‘Black’.
No.
Group
1 Sandra Bullock Gold 2 Bill Clinton Gold 3 Cindy Crawford Gold 4 Tom Cruise Gold 5 Bill Gates Black 6 Whitney Houston Gold 7 Michael Jordan Gold 8 Jay Leno Black 9 David Letterman Black 10 Will Smith Gold
Firstname
Lastname
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 39ICFP’02ICFP’02
Results
Rule-based style“If PacMan loses all his lives, its game over.”
Some use of Constraint style: “Pacman cannot go through a wall.”
Rule-based style“If PacMan loses all his lives, its game over.”
Some use of Constraint style: “Pacman cannot go through a wall.”
Aggregate operations instead of iterations“The monsters turn blue and run away”
“Subtract 20,000 from all elements in Round 2”
— These tend to eliminate control structures
Aggregate operations instead of iterations“The monsters turn blue and run away”
“Subtract 20,000 from all elements in Round 2”
— These tend to eliminate control structures
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 40ICFP’02ICFP’02
More Results
The words “AND” and “THEN” often used for sequencing instead of as a logical operator
“The monsters turn color and start to back up.”
The words “AND” and “THEN” often used for sequencing instead of as a logical operator
“The monsters turn color and start to back up.”
Boolean expression (AND, OR) not common Usually had mutually exclusive rules
“If I press the up arrow, PacMan goes up. If I press the down arrow, PacMan goes down, …”
General case first, then exceptions“When you encounter a ghost, it should kill you.
But if you get a big pill first you can eat them.”
Boolean expression (AND, OR) not common Usually had mutually exclusive rules
“If I press the up arrow, PacMan goes up. If I press the down arrow, PacMan goes down, …”
General case first, then exceptions“When you encounter a ghost, it should kill you.
But if you get a big pill first you can eat them.”
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 41ICFP’02ICFP’02
Yet More Results
Most arithmetic used natural language style“When PacMan eats a big dot, the score goes up 100.”
Most arithmetic used natural language style“When PacMan eats a big dot, the score goes up 100.”
Operations suggest data as lists, not arrays People don’t make space before inserting
Objects normally moving“If PacMan hits a wall, he stops.”
so objects remember their own state
2/3 of the first study subjects drew pictures Usually to define the initial state
Operations suggest data as lists, not arrays People don’t make space before inserting
Objects normally moving“If PacMan hits a wall, he stops.”
so objects remember their own state
2/3 of the first study subjects drew pictures Usually to define the initial state
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 42ICFP’02ICFP’02
Third Study: Select Objects from a Group
Concentrate on a known problematic area Use of AND, OR, NOT
Often eliminated from Web searching Newsweek reports that less than 6% of users
manage to use “and”, “or”, “+”, “-” Still dominant in all programming languages
First: generate queries given results Then, answer queries Form-based and Textual formats Order was counter-balanced
Concentrate on a known problematic area Use of AND, OR, NOT
Often eliminated from Web searching Newsweek reports that less than 6% of users
manage to use “and”, “or”, “+”, “-” Still dominant in all programming languages
First: generate queries given results Then, answer queries Form-based and Textual formats Order was counter-balanced
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 43ICFP’02ICFP’02
Generate Queries
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 44ICFP’02ICFP’02
Answer Queries
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 45ICFP’02ICFP’02
Results
Using “unless” did not help accuracy“select the objects that are blue unless the objects are square”vs.“select the objects that match blue and not square
Using “unless” did not help accuracy“select the objects that are blue unless the objects are square”vs.“select the objects that match blue and not square
“And” was a Boolean conjunction sometimes“select the objects that match blue and circle”vs.“select the objects that match blue and the objects that match circle”
Precedence of “not” varied“select the objects that match not red and square”
64% interpreted as “(not red) and square” “select the objects that match not triangle or green”
67% interpreted as “not (triangle or green)”
“And” was a Boolean conjunction sometimes“select the objects that match blue and circle”vs.“select the objects that match blue and the objects that match circle”
Precedence of “not” varied“select the objects that match not red and square”
64% interpreted as “(not red) and square” “select the objects that match not triangle or green”
67% interpreted as “not (triangle or green)”
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 46ICFP’02ICFP’02
More results
2-D forms helped for generation 94% correct with match forms, vs.
85% correct with text (p<.0001)
2-D forms helped for generation 94% correct with match forms, vs.
85% correct with text (p<.0001)
(blue and not square) or (circle and not green)
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 47ICFP’02ICFP’02
Implications for New Languages
For increased usability for novices: Use event-based style for dynamic events Work to minimize the need for control structures and
variables Provide operations on groups of objects Data structures that combine the capabilities of
lists + arrays + sets Support simple arithmetic in natural language style
(“add 1 to score”) Avoid the use of the word “and” altogether
For increased usability for novices: Use event-based style for dynamic events Work to minimize the need for control structures and
variables Provide operations on groups of objects Data structures that combine the capabilities of
lists + arrays + sets Support simple arithmetic in natural language style
(“add 1 to score”) Avoid the use of the word “and” altogether
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 48ICFP’02ICFP’02
New Language and System: HANDS
Video
Human-centered Advances for Novices to Develop Software
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 49ICFP’02ICFP’02
Properties of HANDS
Goal: Allow children age 10 to createinteractive games and simulations Programming in the small (in the tiny)
Event based computation model Metaphor of agent manipulating cards All data is visible as properties of the cards All operations work on singletons or lists
No distinction in syntax Can generate lists on the fly with queries Minimize need for control structures Minimize need for local variables
Goal: Allow children age 10 to createinteractive games and simulations Programming in the small (in the tiny)
Event based computation model Metaphor of agent manipulating cards All data is visible as properties of the cards All operations work on singletons or lists
No distinction in syntax Can generate lists on the fly with queries Minimize need for control structures Minimize need for local variables
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 50ICFP’02ICFP’02
More Properties of Hands
Verbose Language Easier to read
No precedence Does use parentheses
But just one kind!
Environment provide lots of help with syntax and graphics
Tries to be extremely consistent, and also apply other HCI rules For example, combines IF, CASE (switch), and
COND (from Lisp) into one construct
Verbose Language Easier to read
No precedence Does use parentheses
But just one kind!
Environment provide lots of help with syntax and graphics
Tries to be extremely consistent, and also apply other HCI rules For example, combines IF, CASE (switch), and
COND (from Lisp) into one construct
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 51ICFP’02ICFP’02
Conclusions
Much more research needed on the human side of programming
Usability of languages and environments can be improved
Claims about usability can be tested Languages can be evaluated using HCI principles and
techniques
If you want a useable and learnable programming language, there are data and techniques available that can help.
Much more research needed on the human side of programming
Usability of languages and environments can be improved
Claims about usability can be tested Languages can be evaluated using HCI principles and
techniques
If you want a useable and learnable programming language, there are data and techniques available that can help.
Brad MyersBrad MyersCMU - HCI InstituteCMU - HCI Institute 52ICFP’02ICFP’02
Credits
Support for this research has come in part from the National Science Foundation under
Grant No. IRI-9900452
andGrant No. IIS-9817527
For more information, see:
http://www.cs.cmu.edu/~NatProg
Support for this research has come in part from the National Science Foundation under
Grant No. IRI-9900452
andGrant No. IIS-9817527
For more information, see:
http://www.cs.cmu.edu/~NatProg
53
Towards MoreNatural FunctionalProgramming Languages
Towards MoreNatural FunctionalProgramming Languages
Brad A. MyersBrad A. MyersHuman-Computer Interaction InstituteHuman-Computer Interaction InstituteSchool of Computer ScienceSchool of Computer ScienceCarnegie Mellon UniversityCarnegie Mellon University
http://www.cs.cmu.edu/~bamhttp://www.cs.cmu.edu/~bamhttp://www.cs.cmu.edu/~NatProghttp://www.cs.cmu.edu/[email protected]@cs.cmu.edu
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