CNC Heart

The F# Journal just published an article about mechatronics:
"A simple way to create a cheap CNC milling machine is to fit a Dremel rotary tool to a cheap open-framed 3D printer such as a Printrbot. The same GCode used for 3D printing can then be used to mill. This article explains how F# can be used to generate GCode to control a CNC milling machine in order to carve out some laminar shapes including a cirle and a heart..."

To read this article and more, subscribe to The F# Journal today!

Copying sequences of records to and from Excel

The F# Journal just published an article about interoperability and reflection:
"This article walks through the design and implementation of a small library that allows sequences of values of F# record types to be read from and written to Excel easily. The implementation includes a signature file with Intellisense documentation and example F# script files..."

To read this article and more, subscribe to The F# Journal today!

Call graph visualizer

The F# Journal just published an article about metaprogramming:
"The call graph of a program is the network of functions and caller-callee dependencies between them. This article walks through the design and implementation of a simple F# program that extracts the call graph of a reflected definition and visualizes it using the GraphViz toolkit..."

To read this article and more, subscribe to The F# Journal today!

Function call performance on .NET

The F# Journal just published an article about performance:
"In order to write efficient programs it is essential to have an accurate mental model of the cost of various operations. Function calls are one of the most important operations. This article examines various kinds of function calls and other constructs that are used equivalently and studies their performance in detail..."
To read this article and more, subscribe to The F# Journal today!

BCL vs F#: lists

The F# Journal just published an article about libraries:
"The new immutable collections library for the BCL includes a several purely functional data structures. This article is the first in a series comparing and contrasting F# collections with these new BCL counterparts, starting with the humble list..."
To read this article and more, subscribe to The F# Journal today!

Parsing ints quickly

The built-in .NET library functions for parsing integers are very easy to use but a lower-level approach can be around 6x faster. Here is a function that parses a sequence of 32-bit integers:

  let intsOfString (s: string) =

    let ints = ResizeArray()

    let rec inside n i =

      if i = s.Length then

        ints.Add n

      else

        let c = s.[i]

        if '0' <= c && c <= '9' then

          inside (10*n + int c - 48) (i+1)

        else

          ints.Add n

          outside(i+1)

    and outside i =

      if i < s.Length then

        let c = s.[i]

        if '0' <= c && c <= '9' then

          inside (int c - 48) (i+1)

        else

          outside (i+1)

    outside 0

    ints.ToArray()

For example:

> intsOfString "123 456 789";;

val it : int [] = [|123; 456; 789|]

Using the F# CodeDOM to develop a minimal IDE

The F# Journal just published an article about metaprogramming:
"The F# Code DOM and AvalonEdit WPF control provide a great basis for building an integrated development environment for the F# programming language. This article walks through a simple graphical IDE written in 100 lines of F# code that provides error throwback..."
To read this article and more, subscribe to The F# Journal today!

Bit tricks in F#: integer logarithm

The following function computes the base-2 logarithm of the given integer:

let log2 v =

  let mutable v, r = v, 0

  if v &&& 0xFFFF0000 <> 0 then

    let s = 1 <<< 4

    v <- v >>> s

    r <- r ||| s

  if v &&& 0xFF00 <> 0 then

    let s = 1 <<< 3

    v <- v >>> s

    r <- r ||| s

  if v &&& 0xF0 <> 0 then

    let s = 1 <<< 2

    v <- v >>> s

    r <- r ||| s

  if v &&& 0xC <> 0 then

    let s = 1 <<< 1

    v <- v >>> s

    r <- r ||| s

  if v &&& 0x2 <> 0 then

    let s = 1 <<< 0

    r <- r ||| s

  r