The document summarizes the history of computing and functional programming through key figures such as Alonzo Church who invented the λ-calculus, Alan Turing who created the Turing machine, John von Neumann who established modern computer architecture, John McCarthy who created the Lisp language based on λ-calculus, and Edsger Dijkstra who argued against using GOTO statements. It then discusses how features like mutation and pointers were added to languages but can be harmful, and compares recursion in functional programming to GOTO.

1. Hitchhiker's Guide to
Functional Programming

2. Significantly trivialized
history of computing

3. Alonzo Church
Researched decidability of
algorithms and invented a
generic model of calculation –
the λ-calculus (early 1930s*)
*see https://en.wikipedia.org/wiki/Lambda_calculus

4. Alan Turing
Created a model of a generic
computer – the Universal Turing
machine (ca. 1936*)
*see https://en.wikipedia.org/wiki/Turing_machine

5. John von
Neumann
Created the architecture of
modern computers based
on the Universal Turing
machine (early 1940s*)
*see https://en.wikipedia.org/wiki/Von_Neumann_architecture

6. And PL features exploded...
GOTO, mutation, pointers, null refs, exceptions,
floating point numbers, inheritance, interfaces,
threads…
See http://blog.ploeh.dk/2015/04/13/less-is-more-language-features/ for a discussion of harmful PL features

7. John McCarthy
Created Lisp language based on
the λ-calculus and featuring
macros (ca. 1958*)
*see http://www-formal.stanford.edu/jmc/history/lisp/lisp.html

8. Edsger Dijkstra
Made a case against the
GOTO statement (in 1968*)
*see https://en.wikipedia.org/wiki/Edsger_W._Dijkstra

9. A case against mutation
It’s about time to ban the next offender

10. What’s wrong with this code?
int sum = 0;
for (int i = 1; i <= 10; i++)
{
if (i % 2 == 0)
sum += i * i;
}
System.out.println(sum);

11. Refactoring exercise

12. Erik Meijer
Recursion is GOTO of
functional programming

13. ● λ-Calculus is a model of computation
● Program is data, generic evaluation algorithm
● Turing machine is a model of a computer
● Program is algorithm
Turing machine and λ-calculus are proven equivalent in terms of computability
Summary

14. Learn More (click on the images)

15. Questions?