3 ms·

"He also said that there's no mechanism to compensate for the absence of duck typing. In Haskell, at least, there are type classes which allow you to make your

by dan00 15y ago

"He also said that there's no mechanism to compensate for the absence of duck typing. In Haskell, at least, there are type classes which allow you to make your types as duck as you would wish, maybe slightly less." I think that type classes are the way to go. Duck typing is mostly popular because multiple inheritance sucks, and because inherting a class to only overload a method sucks. Languages like Ruby, Python or Perl are so popular because they are less verbose than Java or C++, with the disadvantage, that the compiler can't help you that much. Haskell is a language that combines the advantages, less verbosity with a helping compiler, and a static type system that rocks.

rit 15y ago
While this is a statement in some ways of preference it is a reasonable comment; not sure why it's getting downvoted. However, can you clarify why you would argue for type classes over duck/structural typing? You indicate that 'type classes are the way to go' but don't explain why. Scala of course does have a form of Type Classes and while they tend to be what I reach for more often than Structural Types in Scala, it doesn't obviate Structural Types completely and I'd be interested in analysis of the diffs.
- kscaldef 15y ago
  With dynamic duck typing you just have to hope the object actually quacks. With type classes, the compiler proves it quacks.
- dan00 15y ago
  "However, can you clarify why you would argue for type classes over duck/structural typing? You indicate that 'type classes are the way to go' but don't explain why." Like kscaldef said, you know at compiletime if something can quack, and the overhead for doing this is quite small. Haskell: instance Quacker MySpecialDuck where quack = "qqquuuuuuaaaaaakkkkk" "Scala of course does have a form of Type Classes and while they tend to be what I reach for more often than Structural Types in Scala, it doesn't obviate Structural Types completely and I'd be interested in analysis of the diffs." In which cases do you need duck typing? Adding dynamically a method to a class?

by dan00 15y ago

rit 15y ago

While this is a statement in some ways of preference it is a reasonable comment; not sure why it's getting downvoted. However, can you clarify why you would argue for type classes over duck/structural typing? You indicate that 'type classes are the way to go' but don't explain why. Scala of course does have a form of Type Classes and while they tend to be what I reach for more often than Structural Types in Scala, it doesn't obviate Structural Types completely and I'd be interested in analysis of the diffs.

kscaldef 15y ago
With dynamic duck typing you just have to hope the object actually quacks. With type classes, the compiler proves it quacks.
dan00 15y ago
"However, can you clarify why you would argue for type classes over duck/structural typing? You indicate that 'type classes are the way to go' but don't explain why." Like kscaldef said, you know at compiletime if something can quack, and the overhead for doing this is quite small. Haskell: instance Quacker MySpecialDuck where quack = "qqquuuuuuaaaaaakkkkk" "Scala of course does have a form of Type Classes and while they tend to be what I reach for more often than Structural Types in Scala, it doesn't obviate Structural Types completely and I'd be interested in analysis of the diffs." In which cases do you need duck typing? Adding dynamically a method to a class?