Declarative Thinking & Programming Florian Wilhelm - - PowerPoint PPT Presentation

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Declarative Thinking & Programming Florian Wilhelm - - PowerPoint PPT Presentation

Mar 16, 2023 442 likes •722 views

Declarative Thinking & Programming Florian Wilhelm EuroPython, Rimini, 2017-07-13 Dr. Florian Wilhelm Data Scientist@inovex Contributor to Pandas, Scikit-Learn, Scipy etc. @FlorianWilhelm Creator of PyScaffold FlorianWilhelm

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Declarative Thinking & Programming

Florian Wilhelm

EuroPython, Rimini, 2017-07-13

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@FlorianWilhelm

  • FlorianWilhelm

florianwilhelm.info

  • Dr. Florian Wilhelm

Data Scientist@inovex Contributor to Pandas, Scikit-Learn, Scipy etc. Creator of PyScaffold

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Outline

  • 1. Motivation & Concept
  • 2. Examples
  • 3. Math Riddle
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Motivation

House-warming party with your friends

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Motivation

What is the actual task?

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Level of Abstraction

Right level of abstraction given a task What is needed to describe the problem?

map & reduce

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Imperative vs. Declarative

How vs. What imperative declarative

  • ver-specification,

detailed instructions, ... separation of concerns, single level of abstraction, ... depending on the level of abstraction

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Leaky Abstractions

Law of Leaky Abstractions by Spolsky: “All non-trivial abstractions, to some degree, are leaky.”

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Outline

  • 1. Motivation & Concept
  • 2. Examples
  • 3. Math Riddle
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Example 1:

List of squared number from 1 to 10 imperative: declarative:

List Comprehensions

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Example 2:

Dispatching with respect to some argument Imperative:

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Example 2: Dictionaries

Dispatching with respect to some argument Declarative:

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Example 3:

Find Plagiarism How many sentences of work A are equal to my work B?

Set Theory Sets

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Example 4: Configuration Files

Python modules vs markup languages

YAML

vs

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Outline

  • 1. Motivation & Concept
  • 2. Examples
  • 3. Math Riddle
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16 Quelle: Die Zeit, Logelei 52, http://www.zeit.de/2016/52/spiele-logelei-52

Math Riddle

horizontal: A: digit sum of horizontal C, C: prime number, E: palindrome, G: multiple of the backward number of horizontal A, ... vertical: All numbers are square numbers.

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Datalog

  • declarative logic programming
  • subset of Prolog
  • query language for deductive DBs
  • other use-cases: security, data integration, information

extraction, networking, program analysis etc. PyDatalog: https://sites.google.com/site/pydatalog/home Features

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PyDatalog

Rules & Facts Read the leftmost <= as if Is X a square number? Is X divisible by Y?

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PyDatalog

Rules & Facts Is X prime?

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PyDatalog

Rules & Facts Map digits to number

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Math Riddle

Keep the number of solutions low at all times Leaky Abstraction

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Math Riddle

Upper left corner A2, A3 are digits from [1...9] and number A2 A3 is prime

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23 http://www.florianwilhelm.info/2017/07/declarative_thinking_and_programming/

Math Riddle

Solution Querying the knowledge base: Solution:

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Other Applications

NixOS

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Summary

Advantages of Declarative Programming

  • improved readability of our code
  • reduced number of errors
  • increased performance
  • separation of concerns

„Declarative programming means finding the right abstraction level describing the problem“

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26 Find more details under http://florianwilhelm.info/2017/07/declarative_thinking_and_programming/

Thanks for your Attention! Questions?