Out of the Tar Pit

Rasmus Buchmann & Maximilian Klein

Last Talk

• Fun
• Creative
• Powerful

Biggest Obstacle?

Biggest Obstacle?

Stuff doesn't work ™

Biggest Obstacle?

Stuff doesn't work ™

The question is: Why?

"Out of the Tar Pit"

One cannot hope to develop, maintain or improve a large program if one is unable to understand it

Reasons

• Complexity
• Control flow
• Code Volume

Focus

Complexity

State

Have you tried turning it off and on again?

When [programmers] encounter complexity, they consider it a challenge to overcome, rather than an obstacle to remove. Overcoming complexity isn't work, it's waste.

Example

      
std::string WhatDoIDo?(const std::vector & dirs , char separator) {
  std::vector::const_iterator vsi = dirs.begin();
  int mCC = vsi->length();
  std::string compareString = *vsi;
  for (vsi = dirs.begin() + 1; vsi != dirs.end(); vsi++) {
    std::pair p =
      std::mismatch(compareString.begin(), compareString.end(), vsi->begin());
     if ((p.first - compareString.begin()) < mCC)
       mCC = p.first - compareString.begin();
  }
  std::string::size_type found = compareString.rfind(separator, mCC);
  return compareString.substr(0 , found);
}
  

Keep in mind

• Pointer? Reference?
• Loop boundaries?
• Types?
• Memleaks?
• Threadsafe?
• Depends on state?

Keep in mind

• Pointer? Reference?
• Loop boundaries?
• Types?
• Memleaks?
• Threadsafe?
• Depends on state?

Keep in mind

• Pointer? Reference?
• Loop boundaries?
• Types?
• Memleaks?
• Threadsafe?
• Depends on state?

Keep in mind

• Pointer? Reference?
• Loop boundaries?
• Types?
• Memleaks?
• Threadsafe?
• Depends on state?

Keep in mind

• Pointer? Reference?
• Loop boundaries?
• Types?
• Memleaks?
• Threadsafe?
• Depends on state?

Keep in mind

• Pointer? Reference?
• Loop boundaries?
• Types?
• Memleaks?
• Threadsafe?
• Depends on state?

Keep in mind

• Pointer? Reference?
• Loop boundaries?
• Types?
• Memleaks?
• Threadsafe?
• Depends on state?

Keep in mind

• Pointer? Reference?
• Loop boundaries?
• Types?
• Memleaks?
• Threadsafe?
• Depends on state?

Attention is limited

• "Magic number 7"
• Clutter is complexity too!
• It's only one (simple) function!
• Adds to the problems listed before

Simple Example

Why is that a problem?

Programming is hard, right?

Why is that a problem?

None of this complexity comes from the task we want to solve!

Traditional solutions

• Abstraction
• Encapsulation
• Modularization
• OOP

Traditional problems

• Abstraction - Not really
• Encapsulation - Hidden State
• Modularization - See last talk :)
• OOP - The new spaghetti code?

"I invented the term Object-Oriented and I can tell you I did not have C++ in mind."

What can we do?

• Make elimination of incidental complexity primary goal
• Learn about alternatives
• Eliminate unnecessary state
• Keep rest as simple as possible

Some suggestions

• The right tool for the job
• Correctness over performance
• Data is Data is Data
• Simple isn't easy

The right tool

Choose the right language/paradigm!

Prerequisite:

Know more than one...

New languages?

Stevey's Blog Rants

Haskell Researchers Announce Discovery of Industry Programmer Who Gives a Sh*t

[...] Programming languages are not merely technologies, but habits of mind as well, and nothing changes slower

Sapir-Whorf

Well designed languages introduce new concepts and ways to think about programs

Even if you're not going to use them directly!

Some suggestions

• Lisp
• Python
• Haskell
• Erlang
• Clojure
• Elm

Every sufficiently advanced program includes an ad-hoc, informally specified, slow, bug-ridden implementation of half of Common Lisp

Lisp

• Incredibly powerful macro system
• Homoiconic - Code is data
• Simplicity and elegance - Common Lisp has only seven core constructs and basically no syntax!

Python

• The ultimate "Get Things Done" language
• Great libraries for everything
• Vastly useful for scientific computing
• Instructive example of hidden state problems

Haskell

• The pure, functional language
• Amazing type system
• True abstractions
• Impress your friends with category theory

Erlang

• Distributed system awesomeness
• Primary actor model example
• Strong FFI and binary support
• Unique error handling

Others

• Clojure - Pragmatic functional programming
• Elm - UIs without callbacks
• Prolog - Logic programming
• Perl - Write only programming
• FORTRAN - The Coelacanth of computer science
• COBOL - COmmon Boilerplate Oriented Language

Summary

Invent new ways to avoid problems rather than new hacks to work around them

Summary

Work towards writing declarative programs, rather than imperative

Systems everywhere

Usually never writing an isolated program - heterogenity

Correctness over performance

Premature optimization is the root of all evil.

Example: Locks

Alternatives: STM, Erlang style message passing, etc... Not as efficient, but:

Example: Locks

• Works 100%
• Saves mental capacity
• Might even be faster

Rule of thumb

Optimize at the very last step, it will frequently be unnecessary

Even Better

Why should you be concerned with performance at all?

Data is Data is Data

...is not an Object!

Don't wrap what is essentially data in a class!

Use Data to

• Alleviate injection problem
• Unlock powerful abstractions
• Get Serialization/Networking for free
• Decoupling via queues
• Eliminate unnecessary state

Immutable Data

• Saves considerable headache
• Simplifies reasoning about programs
• Powerful for multithreading
• Easy to use even in Java or C++
• More in upcoming talk!

Simple isn't easy

Two meanings

• It's hard work to design a program which is simple
• What is easiest to learn might not be the most simple solution

Further Reading/Watching/Fun

• Structure and Interpretation of Computer Programs (!)
• Learn you a Haskell for great good!
• Write yourself a scheme in 48 hours
• Simplicity ain't easy (Stuart Halloway)
• The Value of Values (Rich Hickey)
• Clojure Concurrency (Rich Hickey)

• Why Scala? (Venkat Subramanian)
• Wat - Destroy all Software Talks
• Beating the averages (Paul Graham)
• Stevey's Blog Rants
• http://elm-lang.org/ Beispiele!

Thank you for your attention!

Topic:Bret!