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Monads should be a familiar concept for the seasoned C# programmer. LINQ's 'from in' syntax and the haskell monad 'do' syntax are almost the same! Heck, the

Monads should be a familiar concept for the seasoned C# programmer. LINQ's 'from in' syntax and the haskell monad 'do' syntax are almost the same! Heck, the type signature of SelectMany and (>>=) are even the same! (>>=) :: m a -> (a -> m b) -> m b and public static IEnumerable<TResult> SelectMany<TSource, TResult>( this IEnumerable<TSource> source, Func<TSource, IEnumerable<TResult>> selector ) m = IEnumerable b = TResult a = TSource => m<a> SelectMany<a,b>(this m<a> source, Func<a,m<b>> selector) The type signatures are _EXACTLY_ the same. This isn't a coincidence. LINQ is actually a monad :) So I think taking this approach to explain the Monad voodoo to a C# programmer is the way to go. He actually uses them already :)

daknok 14y ago
LINQ is very similar to the List monad, specifically.
chadzawistowski 14y ago
Further proof for my personal conviction that C# is a very interesting, progressive language which masquerades as a Java clone. I once copied the style of a maybe monad using LINQ - the WinRT apis lack a "FileExists?" method, so I used LINQ to search a directory's contents for a filename. An IEnumerable of size of zero represented None, and size one represented Some. Unfortunately, a simple try/catch around an attempt to open the desired file was more efficient and clearer to understand.
- daknok 14y ago
  You should use try/catch; branching would imply a race condition in a multithreaded environment (what if another process deletes the file between the check and the use of the file?).
- krallja 14y ago
  LINQ has an .Empty() extension method, and you should use that instead of .Count()==0 when determining if an expression is empty.
snprbob86 14y ago
Likewise, Scala's "for" loop compiles to calls to map and flatMap, which are the same as Select and SelectMany, which represent the list monad. You can use map, flatMap, and for notation in lieu of a more generally named do syntax.
runT1ME 14y ago
It goes beyond that . LINQ isn't a monad, it's monadic syntax for any monad. It just so happens that the one everyone uses is IEnumerable. Here, I wrote the Reader monad for IoC to show it could be done: https://gist.github.com/vmarquez/4640678 https://gist.github.com/vmarquez/4640678

daknok 14y ago

LINQ is very similar to the List monad, specifically.

chadzawistowski 14y ago

Further proof for my personal conviction that C# is a very interesting, progressive language which masquerades as a Java clone. I once copied the style of a maybe monad using LINQ - the WinRT apis lack a "FileExists?" method, so I used LINQ to search a directory's contents for a filename. An IEnumerable of size of zero represented None, and size one represented Some. Unfortunately, a simple try/catch around an attempt to open the desired file was more efficient and clearer to understand.

daknok 14y ago
You should use try/catch; branching would imply a race condition in a multithreaded environment (what if another process deletes the file between the check and the use of the file?).
krallja 14y ago
LINQ has an .Empty() extension method, and you should use that instead of .Count()==0 when determining if an expression is empty.

snprbob86 14y ago

Likewise, Scala's "for" loop compiles to calls to map and flatMap, which are the same as Select and SelectMany, which represent the list monad. You can use map, flatMap, and for notation in lieu of a more generally named do syntax.

runT1ME 14y ago

It goes beyond that . LINQ isn't a monad, it's monadic syntax for any monad. It just so happens that the one everyone uses is IEnumerable. Here, I wrote the Reader monad for IoC to show it could be done: https://gist.github.com/vmarquez/4640678 https://gist.github.com/vmarquez/4640678