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Reading Code

Marit van Dijk
November 07, 2023
110

Reading Code

As developers, we spend a lot of time learning to write code, while spending little to no time learning to read code. Meanwhile, we often spend more time reading code than actually writing it. Shouldn’t we be spending at least the same amount of time and effort improving this skill? Deliberate practice can help us get better at reading code. Learning how to better read and understand code, can in turn teach us what makes code readable. This might even help us to write code that is easier to read.

In this talk we will discuss the benefits of deliberately practicing reading code in a code reading club or session without an IDE, as well as common strategies to navigate a new codebase and familiarise ourselves with the code using the IDE.

Marit van Dijk

November 07, 2023
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Transcript

  1. Reading Code
    FooConf - Nov 7, 2023
    https://maritvandijk.com/

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  2. Reading Code
    • We spend more time reading code than writing code

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  3. Reading Code
    We read code when:

    • adding features


    fi
    xing bugs

    • understanding a new system

    • doing code reviews

    • learning new technologies

    • etc.

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  4. Reading Code
    "developers on average spend as much as 58% of their time comprehending
    existing source code"

    -

    Felienne Hermans,
    The Programmer's Brain

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  5. Reading Code
    • We spend more time reading code than writing code

    • But we don't practice reading code explicitly (much)

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  6. Reading Code
    "How to teach programming (and other things)?" by Felienne Hermans
    https://www.youtube.com/watch?v=g1ib43q3uXQ

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  7. Reading Code
    • What if we practice reading code explicitly?

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  8. Code Reading Club
    • Code Reading Club
    https://codereading.club/

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  9. Code Reading Club
    • Printed code

    • Structured exercises

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  10. Examples of exercises
    • First glance

    • Identify components & relationships

    • Most important lines

    • Identify concepts

    • Summary

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  11. Code Reading Club
    Learned about ...

    • reading code

    • other peoples' perspectives

    • noticing my own assumptions

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  12. Structured exercises
    • Code Reading Club Resources:

    https://github.com/CodeReadingClubs/Resources

    • The Programmer's Brain - Felienne Hermans

    • Code Reading in Practice - Felienne Hermans & Gien Verschatse

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  13. Reading Code

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  14. Reasons code is confusing
    1. Lack of knowledge

    2. Lack of information

    3. Lack of processing power in the brain

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  15. Lack of knowledge
    • Programming domain
    • Language / syntax

    • Programming constructs / algorithms

    • Business domain
    • Domain concepts

    • Business logic

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  16. Dealing with a lack of knowledge
    • Create a list

    • Research

    • Memorize

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  17. Lack of information
    • Unknown details

    • Unfamiliar names

    • Code connected in unknown ways

    • Too many things at once

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  18. Dealing with lack of information
    • Chunking

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  19. Lack of processing power in the brain
    • Too many processing steps

    • Too many variables

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  20. Dealing with lack of processing power in the brain
    • Memory aids

    • Dependency graph

    • State table

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  21. Dependency graph

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  22. State table
    public class NestedLoop {
    public static void main(String[] args) {
    for (int i = 0; i < 2; i++) {
    System.out.println("i is: " + i);
    for (int j = 0; j < 2; j++) {
    System.out.println("j is: " + j);
    }
    }
    }
    }

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  23. Reading Code
    Understanding a piece of code

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  24. Reading Code
    • Structured exercises

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  25. Dimensions of code reading
    • Structure

    • Domain

    • Concepts

    • Context

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  26. Structure
    Code is not read linearly

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  27. Domain
    • Behavior

    • Data

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  28. Concepts

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  29. Reading Code
    • Context

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  30. Help in the IDE
    • Structure / Restructure

    • Domain

    • Behavior

    • Syntax highlighting & hints

    • Context

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  31. Strategies
    • Structure

    • Identify components & relationships

    • Identify concepts

    • Gain context

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  32. A slice of the application

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  33. Find a starting point

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  34. Find a starting point
    • Generic
    • Main method

    • Endpoint

    • Speci
    fi
    c
    • Error message / Exception

    • Logic / Functionality

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  35. Help in the IDE
    • Search

    • Navigate

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  36. Strategies
    • A slice of the application

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  37. Reading Code
    The bigger picture

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  38. Understanding a new code base
    • Joining a new team / organisation

    • Using a new code base

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  39. Reading Code
    • What does the code do?

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  40. Context

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  41. Reading Code
    A good place to start:

    • Check out the code

    • See if you can build it

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  42. Help in the IDE
    • README

    • Project structure

    • Dependencies

    • Diagrams

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  43. Strategies
    • Identify components

    • Identify relationships / dependencies

    • Identify concepts

    • Gain context

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  44. Reading Code
    What's next?

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  45. Reading code
    Slides & More
    https://maritvandijk.com/presentations/reading-code/

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  46. Code reading exercise
    First glance
    The goal of this exercise is to practice getting a
    fi
    rst impression of code.

    (1 min) Independently - Glance at the code
    Note down the
    fi
    rst thing that catches your eye.

    Then note the second thing that catches your eye.

    Think about why you noticed those things
    fi
    rst.

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  47. Code reading exercise
    Dependency graph
    The goal of this exercise is to get a feel for the structure of the code.

    (5 min) Independently - Examine structure
    Variables
    1. Go through the code and underline all variables

    2. Then draw a link between variables and their uses

    Function / method calls
    3. Go through the code and circle all methods / function calls

    4. Then draw a link between methods and their invocations

    Instantiation
    5. Go through the code and draw a box around all instances of classes

    6. Then draw a link between classes and their instances

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  48. Code reading exercise
    Most important lines
    The goal of this exercise is to start to think about which lines in the code
    de
    fi
    ne its essence, have the biggest impact or need to be paid close
    attention to.

    (5 mins) Independently - Identify most important lines
    Brie
    fl
    y discuss what it means to be important as a group (if you want to).
    Then, identify the 5 lines you consider most important.

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  49. Code reading exercise
    Concepts
    (5 min) Individually - Central thematic concepts
    Name the 5 most central concepts of the code. These could be names,
    themes, classes, or information found in comments.

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  50. Code reading exercise
    Summary
    The goal of this exercise is to think about the core purpose or function of
    this code.

    (5 mins) Independently - Summarize
    Try to write down the essence of the code in a few sentences.

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