I think they're using it so that they can use nil as the zero value to indicate the buffer is empty in cases where the zero value is a valid result.
I feel like the comma ok idiom is a better idea here.
I feel like the comma ok idiom is a better idea here.
I see that that was changed already (https://github.com/MoserMichael/rzgrep/commit/764b9ad61a5dbe...)
I think I would not return “ctx.data[0]” for the value returned in case of error, though. That runs the risk of users processing items multiple times if they forget to check for errors.
I would use either
- a fresh new instance of T
- a special instance of T created once (could be passed in to NewCBuf as a value with, to the user, obviously incorrect contents)
The first is cleanest, but may not be performant if creating T’s is costly.
The second may be risky if the returned items are mutable and the caller changes them.
I am not to comfortable with this either, i wonder why golang doesn't have a Maybe/Option monad in its standard library, i mean that's a very widely used pattern, nowadays... or am I missing something here?
Maybe/Option monads in other languages:
https://www.scala-lang.org/api/2.13.3/scala/Option.html
https://docs.oracle.com/javase/8/docs/api/java/util/Optional...
https://wiki.haskell.org/Maybe
I guess they didn't want to copy the T value into the Option instance, but yeah, otherwise you get something like this, or you have to return a pointer.
The go error pattern would need Either, though. In C, that’s ‘union’, but go (rightly so, IMO) didn’t copy that.
Problem is, once you have Either[T,U], you want Either[T,U,V] and then, you want pattern matching. That, like generics, complicates a language.
The go developers don’t want to go there (¿yet?).
I think that's a bit of a stretch, operations on Maybe types can be chained or used with Java streams. You can't do a thing like that with pointers.
They could have dome something like java streams, given that golang has lambdas, but I guess that would not be idiomatic, or something like that...
You do have a point with pattern matching, they don't do that in go. Scala has it, Java is getting pattern matching as some recent addition, but they added the Optional type with java 8.