## Snippets created by Carsten König

• ### Graham scal algorithm for finding the convex hull of a sequence of 2D points

finds the points lying on the convex hull of the given set of points and returns those points in clockwise direction, starting at the point with minimum y-value Remarks: it's a more or less direct implementation of the algorithm named after Ronald Graham that is explained on http://en.wikipedia.org/wiki/Graham_scan you can switch the definition Point for a proper type of your liking - e.g. System.Drawing.Point

39 people like this

Posted: 12 years ago by Carsten König

• ### ZipMap

Helper function to fold an operator over two sequences so {x1; x2; x3; x4; ...} and {y1; y2; y3; y4; ..} is mapped with an operator f to {f x1 y1; f x2 y2; ...} See example

20 people like this

Posted: 12 years ago by Carsten König

• ### sum the nodes in a (not-binary) tree using continuations

you can easily find how to use continuations to iterate over a binary tree but what if the count of children for each node is not known at design time? It's not so obvious how to do this in order to get a tail-recursive method. This short snippet shows how to do this to sum the values of every leaf. The second part demonstrates a general approach for other operations than addition.

26 people like this

Posted: 12 years ago by Carsten König

• ### calculating the distance on earth (with units of measure)

calculating the distance between two locations on earth using haversine formula see http://en.wikipedia.org/wiki/Haversine_formula and implementing it using the posibilities of F#'s unit of measure system to avoid unit-conversion-errors concerning radians convertet the code found here: http://www.movable-type.co.uk/scripts/latlong.html for an concrete implementation

4 people like this

Posted: 12 years ago by Carsten König

• ### Permutations

computes the list of all permutations of a list for example the permutations of [1;2;3] will be [1;2;3]; [1;3;2]; [2;1;3]; [2;3;1]; [3;1;2]; [3;2;1]

2 people like this

Posted: 12 years ago by Carsten König

• ### Curry / Uncurry

Helpers to convert functions that take a 2-tuple to curried functions and vice versa. Very helpfull for the "Zip"-functor together with operators - see example

45 people like this

Posted: 12 years ago by Carsten König

• ### QR-decomoposition of a square-matrix using the Gram-Schmidt method

shows a simple implementation of a vector and matrix type together with a QR-decomposition using the Gram-Schmidt method. The algorithms themselfes are rather easy but I think the implementation of the types and the computations using recursive techniques might be interessting

3 people like this

Posted: 12 years ago by Carsten König

• ### Nullable to Option

it's allways a pain to work with F#'s Option values outside of F# - there you've got the Nullable-class this is a short snippet to convert Nullable<'a> to 'a option

2 people like this

Posted: 12 years ago by Carsten König

• ### Fun with polynoms and inline

for all those wanting to see the (rather unknown) statical interference of type-parameters (in contrast to generic type parameters) in action. I demonstrated this by having som e fun with basic algebra and polynoms

0 people like this

Posted: 12 years ago by Carsten König

• ### Red-Black-Trees with insert

Found an very good article on RS-Trees in Haskell (see: http://www.eecs.usma.edu/webs/people/okasaki/jfp99.ps) It heavyly uses pattern recognition to translate those pesky balance-rules into short code. Bellowe is the simple rewrite of the haskell-implementation in F# - enjoy

6 people like this

Posted: 12 years ago by Carsten König