The Buggy Way of Programming

Rasmus Buchmann & Maximilian Klein

Once you think you know what you are doing you stop looking around for other things [...]
you become blind

Structure

• Creativity
• Reusability
• Simplicity

The Shoe Analog

A Shoe should be

A Shoe should be

A Shoe should be

A Shoe should be

A Shoe should be

A Shoe should be

Implementations differ

Implementations differ

A question of taste... (no right or wrong)

Creativity is bad for Programming ?

• Libraries must have well defined interfaces
• You cannot use APIs without learning those interfaces

No!

• Creativity is vital!
• But it conflicts...

No!

• Creativity is vital!
• But it conflicts... all the time

Simple example

grp = createGroup(rgb(0,0,150));
grp.addTextParagraph("Lorem Ipsum...", rgb(0,0,0));
innerGrp = grp.createGroup(rgb(200,0,0));
innerGrp.drawCenteredText("Hello World", rgb(204,203,10));
  

Simple example

grp = createGroup(rgb(0,0,150));
grp.addTextParagraph("Lorem Ipsum...", rgb(0,0,0));
innerGrp = grp.createGroup(rgb(200,0,0));
innerGrp.drawCenteredText("Hello World", rgb(204,203,10));
  

Simple example

grp = createGroup(rgb(0,0,150));
grp.addTextParagraph("Lorem Ipsum...", rgb(0,0,0));
innerGrp = grp.createGroup(rgb(200,0,0));
innerGrp.drawCenteredText("Hello World", rgb(204,203,10));
  

Simple example 2

content = "<div>Lorem Ipsum ....  \
  <div><center>Hello World</center></div>";
HTMLRenderer.render(content);
  

Simple example 2

content = "<div>Lorem Ipsum ....  \
  <div><center>Hello World</center></div>";
HTMLRenderer.render(content);
  

Simple example 2

content = "<div>Lorem Ipsum ....  \
  <div><center>Hello World</center></div>";
HTMLRenderer.render(content);
  

Google would be impossible when...

Google is possible as...

Google is possible as...

Google is possible as...

What is Important?

No unnecessary information hiding

It is possible to work with Metadata

{
  "Translation" : [1,4,0],
  "Rotation" : [0.4,1,0,0],
  "Metadata" : {
    "RotationType" : "Quaternion",
    "TranslationUnit" : "Centimeter"
  }
}

So, make it possible!

Well...
There is still a problem

How to communicate semantics!... That's hard!

The Library Problem

The Library Problem

The Library Problem

The Library Problem

The Library Problem

In reality there is no LibAnything

The Injection Problem

The Injection Problem

Usually interactions are not that simple...

The Injection Problem

Libraries introduce custom types...

The Injection Problem

Which are used everywhere in MyProgram...

The Injection Problem

    QMatrix3x3 rotation = ...;
    Eigen::Matrix3D eigenRotation;
    for(int i=0; i < 9; i++){
      eigenRotation[i] = rotation[i%3][i/3];
    }
  

The Dependency Problem

Or we use only a subset of the features..

The Dependency Problem

But we are (indirectly) dependent on all features...
And they can have further dependencies...

The Dependency Problem

And sometimes you have to fix problems that are / might be irrelevant for you..

The Semantic Issue

Two function calls with different names...

The Semantic Issue

LibAnything decides to rename the functions...

The Library Problem

• Strong dependence (e.g. through type injection)
• Mostly syntactical dependence

The Library Problem

• Strong dependence (e.g. through type injection)
• Mostly syntactical dependence

Why semantical dependence?

• We know what we want!
• Others are usually experts in the technical details

What's wrong

public int getNextUniqueID(){
    uniqueIdCounter = uniqueIdCounter + 1;
    return uniqueIdCounter;
}

What's wrong

public int getNextUniqueID(){
    uniqueIdCounter = uniqueIdCounter + 1;
    return uniqueIdCounter;
}

But more important!

Even with semantics.. it is impossible to validate it's correctness..

That's sad

Two lines.. and we cannot say if the function works correctly

Let's look at another example

class Counter{
  private int cnt = 0;
  public void increment(){
    cnt = cnt + 1;
  }
  public void decrement(){
    cnt = cnt - 1;
  }
  public int getCount(){
    return cnt;
  }
}

Let's look at another example

class Counter{
  private int cnt = 0;
  public void increment(){
    cnt = cnt + 1;
  }
  public void decrement(){
    cnt = cnt - 1;
  }
  public int getCount(){
    return cnt;
  }
}

Let's look at another example

class Counter{
  private int cnt = 0;
  public void increment(){
    cnt = cnt + 1;
  }
  public void decrement(){
    cnt = cnt - 1;
  }
  public int getCount(){
    return cnt;
  }
}

But you can break it!

But you can break it!

With Multithreading!

But you can break it!

• Simply create two threads.
  1. is constantly incrementing values
  2. is constantly decrementing values

Solutions?

NO LOCKS!

NO LOCKS!
No!

NO LOCKS!
No!No!No!

NO LOCKS!
No!No!No!No!No!

Use Values

Use Values

Immutability is key!

Thank you for your attention!

Topic: Out of the Tar Pit