Sunday, September 20, 2015

F# and Functional Pearls


After encountering the language last year, I've finally gotten around to studying F# from Expert F#. So far, the language has proven much friendlier than Haskell (though it's not really a fair comparison since I'm now more aware of functional constructs).

As practice, I've started implementing some Project Euler problems in F#. I've also been working on porting some Haskell "functional pearls" from Richard Bird's excellent book Pearls of Functional Algorithm Design. The going is slow but rewarding, as it's turning out to be a great way to practice F# while also learning more about functional programming in general.

One chapter that I've worked on is the "countdown" problem, in which the goal is to use some numbers from a given list to generate an arithmetic expression that evaluates to a value as close to target as possible. For example, given a list of numbers [1, 3, 7, 10, 25, 50] and a target of 831, the solution is: 

> display(countdown1 831 [1;3;7;10;25;50]);;

(7+((1+10)*(25+50))) = 832

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