NPRG075

Making programming
easier and learnable

Tomáš Petříček, 309 (3rd floor)
petricek@d3s.mff.cuni.cz
https://tomasp.net | @tomaspetricek

Lectures: Monday 12:20, S7
https://d3s.mff.cuni.cz/teaching/nprg075

Introduction

Programming for non-programmers

What & why

Programming for non-programmers

  • Augmenting human intellect research theme
  • Reducing costs of programming for businesses
  • Computer science & general education
  • Thinking about how to think when programming!

Computational thinking

Is that teaching everyone to code?

What to teach and
how to best do it?

Designing languages for education?

LOGO (1967)

Characteristics of the era

Not just a programming language for kids

Computer environment: people, things, ideas

Computer culture: a way of thinking about thinking

No-code and
low-code

Platforms for creating applications with minimal code

A new take on end-user programming

FLOW-MATIC

High-level business oriented predecessor of COBOL (1957)

Makes coding so easy your company will not need programmers!

Methodology

Programming for non-programmers

  • Metaphors for explaining programming
  • Cognitive models to understand human thinking
  • Finding more manageable kinds of interactions
  • Understanding & assisting with common errors

End-user programming

Making programming super easy

A small matter of programming

End-user programming (1993)

  • Spreadsheets, CAD systems,
    statistical packages
  • Task specific systems

An elusive dream?

  • Can anyone become a programmer?
  • Beyond task-specific?
  • Programmable end-user systems?

End-user programming

① Very high-level
Domain-specific languages

② Spreadsheets
CAD & statistical systems

③ User interaction
New kinds of specifying

High-level languages

FLOW-MATIC (1960s)
English; easily taught to clerical workers

DSLs (2000s)
Small languages for specific problems

Low-code (2020s)
GUI-based entire
app development

Case study: Darklang

Domain-specific abstractions for server-less backends

  • HTTP handler
  • Worker
  • Database
  • CRON job

Notations

Limits of high-level notations

  • Requires a "tidy" problem domain
  • There is no universal language
  • Adaptable notations tend to be complex
  • Cannot (should not?) accept human vagueness

What makes programming hard?

Cognitive obstacles

  • Loss of direct manipulation
    (and the frame problem)
  • Use of (specialized) notation
  • Abstraction for complexity

Attention investment model

  • Cognitive obstacles have cost
  • Programming as an investment
  • When is the gain worth it?

Eliminating cognitive obstacles

  • Spreadsheet-based interfaces
    Avoid abstraction and give immediate feedback
  • Programming by example
    No need for notation and abstraction
  • Direct manipulation
    Manipulate concrete entities & post-hoc abstraction

Spreadsheets as programming

Are they really programming?

  • Domain-specific, but powerful
  • Turing-complete (in a way)
  • Lambdas, macros, extensions

Spreadsheets & programming

  • IDEs can learn about liveness
  • Spreadsheets can learn about software engineering
  • TechDims: Abstraction construction, feedback loops

General-purpose spreadsheets?

(Marasoiu, 2019)

Spreadsheet-based data visualization

Spreadsheet interface for constructing custom charts

What else could we express this way?

Direct manipulation

Complete task manually, have computer repeat it

Industrial robots, graphics editing, task automation, geometry, formatting

How to allow for small variation in behaviour?

Wrangler

(Kandel et al, 2011 )

Data wrangling by direct manipulation

User cleans with data

System builds a script

Attempts to generalize concrete interactions

Programming by example

FlashFill and FlashExtract

  • Write (or select) examples
  • System infers patterns
  • Refine examples to clarify

Implementation

  • Synthesize programs to match
  • Using carefully chosen small language
  • And a suitable search algorithm

Education

Teaching programming & thinking

MIT Artificial Intelligence Lab

Minsky & Papert

"Seymour Papert and Marvin
Minsky thought about thinking, about children's thinking and
about machine's thinking."

LOGO project & language

  • Computers as "native speakers" of mathematics
  • Teach creative and logical thinking
  • Giving children tools to learn (Montessori)

LOGO as a language

Language features

  • Interactive and LISP-inspired
  • Lists, recursion, functional
  • More of an idea than a language

LOGO for education

  • Learning through microworlds
  • Give kids the most powerful language created
  • Powerful ideas: anthropomorphization, metalanguage
TO NOUN
  OUTPUT PICK [BIRDS DOGS ..]
END
TO VERB
 OUTPUT PICK [HATE BITE LOVE]
END
TO ADJECTIVE
  OUTPUT PICK [RED PECULIAR ..]
END

PRINT (SENTENCE ADJECTIVE
  NOUN VERB ADJECTIVE NOUN)

Microworlds

A small domain-specific language for exploring ideas

Turtle graphics is best known example

First LOGO example was for word plays

Turtle microworld

On-screen and floor robots

Great for teaching

Debug by pretending to be the turtle & follow program

Does not blame students ("the turtle has a bug")

Computer science education

Teaching programming thinking today

  • From 1960s idealism to 2020s pragmatism
  • Focus on what we can convincingly study
  • Improving teaching practices & methods
  • Developing better conceptual frameworks

Notional machines

Models for thinking

  • Model of a computer operation
  • Helps understand computation
  • A "useful lie" for teaching

Example notional machines

  • Objects and message passing of Smalltalk
  • LOGO "little people" metaphor
  • Computation as railway track

Little people metaphor

A powerful idea for understanding how programs work

Function instantiation as a "little men" doing (one step of) work

Linked lists (1/2)

Boxes with pointers as connecting arrows

Let's insert 3 in the list between 2 and 4...

Linked lists (2/2)

Boxes with pointers as connecting arrows

Let's insert 3 in the list between 2 and 4...

Useful but does not explain everything that pointers can do!

Computing education

Basic disagreements about the problem

  • Computational thinking & algorithms for all?
  • Creativity as with LOGO and Sonic Pi?
  • History and philosophical problems?
  • How to best teach present-day technology?

Metaphors

Thinking about programming

Metaphors for programming

Essence of human thought?

  • Time as resource, Up as positive, ...
  • Apparent through our language
  • Basic for constructing mathematics?
  • Each has fits and misfits

Metaphors for programming

  • Notional machines (LISP, Smalltalk)
  • Thinking about variables, monads

Two metaphors for variables

Variable as a box

  • You store value in a box
  • Variable "contains" a value
  • What is stored in a name?

Variable as a label

  • Label you place on a value
  • Variable "is" a value
  • What is a name?

Misconceptions

Does the metaphor for variables matter?

  • What is the meaning of multiple assignment?
  • Box can contain multiple values!
  • Label will be for computation or addition
  • Box metaphor wins, but beware of misfits

class Monad m where
 (>>=)  ::
  m a -> (a -> m b) -> m b
 return ::   
  a -> m a

Metaphors for monads

Interface capturing a class of computations

Used for effectful computations in Haskell

How programmers
think about them?

Three metaphors for monads

Symbolic

Meaningless symbolical entity satisfying laws

Box

Container that can be transformed and un-nested

Track

Computation that can proceed in multiple ways

Misconceptions

Common errors in thinking

  • Loops terminate when condition turns false
  • Sequential statements do not wait
  • Variable name has effect on its behaviour
  • Missing else branch stops program

Conclusions

Easier and learnable

Thank you!

Please do keep in touch!

  • Do a final project (and get credit as a bonus)
  • Sign-up for a follow-up seminar
  • Get in touch about MSc or PhD projects

Tomáš Petříček, 309 (3rd floor)
petricek@d3s.mff.cuni.cz
https://tomasp.net | @tomaspetricek
https://d3s.mff.cuni.cz/teaching/nprg075

References (1/3)

End-user programming

Spreadsheets

References (2/3)

Programming by demonstration

Programming by example

References (3/3)

Programming education

Metaphors & misconceptions