Tag: Programming Language

Functional and Declarative Programming in Education (FDPE08)

This conference covers a lot of very interesting topics about the role of functional programming (FP) languages in education (follow the link for ample details). It sounds like a great conference!
(Its co-location with ICFP 2008 is yet another reason to attend, and as FP becomes more popular in the industry today, the question of how to teach FP to imperatively trained programmers becomes especially interesting.)

Emacs influence on Ruby

Who would’ve thought that Ruby’s block ‘end’ keyword was created to facilitate Emacs? Oh man!

When [Matz] was first starting out writing Ruby, he was coding the Emacs ruby-mode.el for it at the same time. He expressed some frustration with modes for other languages like Python and Pascal in which the editor could not look at a line of code and figure out where it should be indented to, so he resolved that Ruby as a language should not fall into that particular trap. With that in mind he chose the end keyword as a block delimiter so that it would be easier to write an Emacs mode for.

Composing Functions with Scheme

In the PLT thread [‘complement'[?] of map] Stephen de Gabriel asked if there was a function that would take any number of functions, and an argument, and then apply the first function to the argument, and apply the second function to the result of the first, and so on.
In PLT Scheme, the function is called ‘compose’. Compose:

Returns a procedure that composes the given functions, applying the last f first and the first f last. The composed functions can consume and produce any number of values, as long as each function produces as many values as the preceding function consumes.

I asked if this was typical FP style, and Noel replied that it is so common that compose is an infix operation in Haskell and ML, as far as he could recall.
Here is an example (from the thread) of how it works using the “Pretty Big” language:

(define pam
  (lambda (datum . proc-list)
    ((apply compose proc-list) datum)))
(pam
 2
 (lambda (n) (/ n 7))
 (lambda (n) (- n 3))
 (lambda (n) (+ n 10))
 (lambda (n) (* n 7)))
> 3

Companies using DSLs with Functional Programming Languages

One of the questions that has been lingering in the back of my mind for a long time is “When should a company use a DSL?”. My stock answer has always been “When it makes sense.”
Perhaps a better way is to answer that question is to look at how companies are actually using them today, rather then to simply guess!
Have a look at the “case studies” section in this presentation on ContractML to see how companies are using DSLs today.
(via cufp)