Functional Programming in the CS Curriculum

1
Functional Programming in the CS Curriculum

• Stuart Reges
• University of Washington

2
The back story(how I ended up on this panel)

• We were in the middle of a heated debate in which
  I almost wanted to strangle Matthias Felleisen
  and Shriram Krishnamurthi

3
The back story(how I ended up on this panel)

• We were in the middle of a heated debate in which
  I almost wanted to strangle Matthias Felleisen
  and Shriram Krishnamurthi
• I said, I wish we could agree on something
  simple, like asking the ACM to require functional
  programming in the CS core

4
The back story(how I ended up on this panel)

• We were in the middle of a heated debate in which
  I almost wanted to strangle Matthias Felleisen
  and Shriram Krishnamurthi
• I said, I wish we could agree on something
  simple, like asking the ACM to require functional
  programming in the CS core
• Matthias hugged me

5
The back story(how I ended up on this panel)

• We were in the middle of a heated debate in which
  I almost wanted to strangle Matthias Felleisen
  and Shriram Krishnamurthi
• I said, I wish we could agree on something
  simple, like asking the ACM to require functional
  programming in the CS core
• Matthias hugged me
• Matthias, Shriram and I wrote a proposal

6
The back story(how I ended up on this panel)

• We were in the middle of a heated debate in which
  I almost wanted to strangle Matthias Felleisen
  and Shriram Krishnamurthi
• I said, I wish we could agree on something
  simple, like asking the ACM to require functional
  programming in the CS core
• Matthias hugged me
• Matthias, Shriram and I wrote a proposal
• It was unanimously approved by 30 PL researchers
  who rarely agree on anything

7
The back story(how I ended up on this panel)

• We were in the middle of a heated debate in which
  I almost wanted to strangle Matthias Felleisen
  and Shriram Krishnamurthi
• I said, I wish we could agree on something
  simple, like asking the ACM to require functional
  programming in the CS core
• Matthias hugged me
• Matthias, Shriram and I wrote a proposal
• It was unanimously approved by 30 PL researchers
  who rarely agree on anything
• We all sang Kumbaya

8
The back story(how I ended up on this panel)

• We were in the middle of a heated debate in which
  I almost wanted to strangle Matthias Felleisen
  and Shriram Krishnamurthi
• I said, I wish we could agree on something
  simple, like asking the ACM to require functional
  programming in the CS core
• Matthias hugged me
• Matthias, Shriram and I wrote a proposal
• It was unanimously approved by 30 PL researchers
  who rarely agree on anything
• We all sang Kumbaya (ok, that parts not true)

9
What did we mean byfunctional programming?
10
What did we mean byfunctional programming?

• I shall not today attempt further to define the
  kinds of material I understand to be embraced
  within that shorthand description and perhaps I
  could never succeed in intelligibly doing so.
  But I know it when I see it.

11
What did we mean byfunctional programming?

• I shall not today attempt further to define the
  kinds of material I understand to be embraced
  within that shorthand description and perhaps I
  could never succeed in intelligibly doing so.
  But I know it when I see it.
• Justice Potter Stewart on obscenity

12
These are a few of myfunctional things

• Functions as first-class entities in a language
  (e.g., can be passed as parameters)
• Higher-order functions (map, filter, reduce)
• Avoidance of mutable state
• Closures (combination of code and context)
• Anonymous functions (lambdas)
• Use of lambda calculus for formal definitions

13
An example from Pythoncompute primes less than
250

• def factors(n)
• return m for m in range(1, n1) if n m
  0
• def is_prime(n)
• return factors(n) 1, n
• gtgtgt filter(is_prime, range(250))
• 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41,
  43, 47,
• 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103,
  107, 109,
• 113, 127, 131, 137, 139, 149, 151, 157, 163, 167,
  173, 179,
• 181, 191, 193, 197, 199, 211, 223, 227, 229, 233,
  239, 241

14
Why functional programming?

• FP stretches students understanding of what
  programming means (what weve called paradigms
  in the past)
• FP constructs are showing up in many popular
  programming languages (Python, Ruby, JavaScript,
  OCaml)
• FP is showing up in industry
• Microsoft F, LINQ
• Google MapReduce
• Yahoo Hadoop
• FP has a rich history dating back to Alonzo
  Church (1936) and with significant interest ever
  since (LISP-1958, ML-1973, Scheme-1975,
  Erlang-1987, Haskell-1990)

15
Our Proposal revenue neutral adjustment to CC2001
16
Comments on FP10

• ACM has a comment period that ran from 6/9/08 to
  7/16/08
• The FP10 proposal received the most comments
• Of the 135 people who commented, at least 130
  were supportive

17
Where do we stand now?

• The review committee was divided in its response
  to the SIGPLAN proposal. On the positive side,
  the committee was convinced that students need
  exposure to more than one programming paradigm,
  for precisely the reasons outlined in the
  proposal. At the same time, there was no
  consensus within the review committee that the
  functional programming paradigm needed to be
  required in all undergraduate computer science
  curriculaWe did not believe that we could
  justify making so far-reaching a change,
  particularly at the level of an interim review.
  Our consensus recommendation is therefore to add
  a new requirement that students acquire facility
  with more than one programming paradigmThe
  review committee also plans to forward both the
  SIGPLAN proposal and the notes from our
  discussions to the next full-scale curriculum
  committee.