Correct by Construction in F#

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Microsoft news and tips » Correct by Construction in F# — Wed, 23 Apr 2008 00:00:18 GMT

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re: Correct by Construction in F#

[ICR] — Wed, 23 Apr 2008 01:18:05 GMT

I realise it's not the same and perhaps not in the spirit of the post, but I always write my switch statements in C# as:

switch(Value)

{

case A:

...

break;

case B:

...

break;

default:

Debug.Assert("ERROR");

}

Not as good as a compile time but the extra runtime check allows you to catch missing code more often.

But I understand the theme of the post. The non-nullilty of things does help to reduce a lot of errors.

re: Correct by Construction in F#

MichaelGG — Wed, 23 Apr 2008 06:26:56 GMT

Yea, top on my wish list for C# 4 is a non-nullable type system and discriminated unions, hopefully with some primitive pattern matching. But I'm sure I'll just be told to go use F# (which is fine by me, as soon as it's shipping in VS!)

Community Convergence XLIII

Charlie Calvert's Community Blog — Thu, 24 Apr 2008 09:11:02 GMT

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re: Correct by Construction in F#

BlindWanderer@gmail.com — Thu, 24 Apr 2008 15:32:08 GMT

I would assume that F# is implicitly adding some non-nullable attribute to it's classes and method parameters. Otherwise how would other languages know not to pass those classes and methods nulls?

re: Correct by Construction in F#

MichaelGG — Thu, 24 Apr 2008 20:38:33 GMT

Blind: Other languages don't know and will pass null; hence with interop you gotta watch it. It's just a sad result of C#/CLS not including some kind of non-nullable type system from the start.

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Chris Smith's completely unique view — Sat, 10 May 2008 01:19:41 GMT

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re: Correct by Construction in F#

David Nelson — Sat, 21 Jun 2008 04:57:23 GMT

I am curious, how does F# deal with situations where null values are legitimate? Null values in programming languages are similar to null values in databases: they can cause problems if used carelessly, but they do have legitimate uses. And not all classes are well-suited to singleton "empty" values.

re: Correct by Construction in F#

Jonathan Allen — Thu, 04 Jun 2009 22:31:45 GMT

> a few special cases

Like everytime you deal with the String type?

F# should have been so much more, but their unwillingness or inability to merge option and null means that my code isn't any safer.