Implementing a Stack in F#. Tail Recursion.

Viral F#

Since Push requires stacks to manipulate its data, we need an implementation of this data structure. There is of course a .NET implementation, however, it is not a “functional” data structure, in a sense that it is mutable. It is easy enough to implement our own, purely functional, immutable stack.

F# list is a logical choice for an underlying implementation. It derives from Seq (i.e. implements all IEnumerable flavors), has a useful length property which we would like to have for our stack as well:

What remains is to implement basic operations, which are all static members of the Stack module.

These are pretty straightforward. pop function has a slight quirk: we would like to return both the value of the head of the stack as well as “the rest” of the stack. So the return type in this case is a tuple.

Another slight irregularity: stack functions work on…

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Why F#?

Didactic Code

If you’ve been following along with my posts over the past six months or so you can probably imagine that I’ve been asked some variation of this post’s title more than a few times. One question that I keep getting is why I chose F# over some other functional languages like Haskell, Erlang, or Scala. The problem with that question though is that it’s predicated on the assumption that I actually set out to learn a functional language. The truth is that moving to F# was more of a long but natural progression from C# rather than a conscious decision.

The story begins about two and a half years ago. I had pretty much burned out and was deep into what I can only begin to describe as a stagnation coma. I stopped attending user group meetings; I cut way back on reading; I pretty much stopped…

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Book Review: F# for C# Developers

This book looks interesting enough to give it a try. I’ll order a copy today.

The Education of a Programmer (Me)

I recently read F# for C# Developers by Tao Liu. As usual, the disclaimer is that I received a copy of the book for free in return for the review. This one was a challenge. Not because of the programming paradigm shift from imperative driven programming in C# to functional programming in F#, but because the density of the book and my having read a different book on F# rather recently.

Mr Liu is most certainly an expert on F#, both from his work at Microsoft and this book. However there were times when I felt a little frustrated in reading the book. My favourite chapter of this book was Chapter 3 where he examines design patterns which can be found in C# and then applies these patterns to F# code. It remains dense reading, but it demonstrates those patterns very well. Mr Liu takes the notion, as I read…

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