Haskell

Sometimes the type system feels backwards. What if I don't want the compiler to infer types for my variables? What if I want the opposite, where it does constraint checking on said variables? For example, instead of inferring the type of the elements of a list, it instead makes sure that they all belong to a particular typeclass. This is a subtle but huge difference that makes it difficult for me to program UIs. It can be done, but it takes more effort than it does in some other languages. Haskell rocks for the non-UI parts, but the UI I leave to an untyped language. Allowing the construction of infinite values leads to some really frustrating errors sometimes. NoMonomorphismRestriction. Bytestring handling bites me in the ass sometimes and you don't know it until your program crashes because you mixed them up improperly. Something is wrong here, when we are losing type information that should have prevented this. Typeclasses should be automatically derived for trivial cases, like witness types, but there's a strong potential for abuse there.

c# / .net:

Classes should be sealed by default There should be no lock statement - instead, you should have specific locking objects, and there should be methods such as Acquire which return disposable lock tokens. Corollary: there shouldn't be a monitor for every object. GetHashCode() and Equals() shouldn't be in System.Object - not everything's suitable for hashing. Instead, have an IdentityComparer which does the same thing, and keep the IComparer<T>, IComparable<T>, IEqualityComparer<T> and IEquatable<T> interfaces for custom comparisons. Poor support for immutability Poor way of discovering extension methods - it should be a much more conscious decision than just the fact that I'm using a namespace.

这些都是我想出来的，明天问我，我会想出一个不同的5个:)

REBOL

REBOL是我最喜欢的语言之一。我不能说我有一个最喜欢的，尽管Haskell排名也很高。

Its odd syntax scares off many developers before they even give it a try. use [email rules url] [ ; A small DSL that sends email to people about URLs. rules: [ some [ into [ set email email! set url url! (send/subject email url reform [ "Check Out" url ]) ] ] ] ; Global context notify: func [ [catch] dsl [block!] ] [ unless parse dsl rules [ throw make error! "You screwed up somehow." ] ] ] notify [ [ a@b.com http://www.google.com ] [ b@c.com http://www.yahoo.com ] ] Recursive dialects are very easy to validate with PARSE but very difficult to evaluate. (Stacks can be helpful here.) REBOL has very poor integration with many popular technologies, particularly XML. I suspect this is partly arrogance, because the REBOL BLOCK! datatype can do almost everything XML can do. However, the real world has XML in it. No Unicode. Thanks to AltMe, REBOL's user community is very insular. I can understand why they want to use AltMe. It's written in REBOL and shows off its strengths. Unfortunately it also puts them off on their own little island.

即将到来的REBOL 3有望解决许多这些问题，除了最后一个。

F#

Type inference is limited. It propagates forward only. F# won't try to infer an object type based on the methods and properties used: you'll get "lookup of indeterminate object type" errors when it doesn't have a clue. One cannot mix floats and ints: 1 + 2.3 is a type error. It's a little awkward to have to create a builder object in order to define a monad or computation expression. In Haskell or Scala, you can define the monad operations directly on the monadic object. Though the #light syntax is preferred, the indentation rules are sometimes not very intuitive or become cumbersome.

VB。网

The behavior AndAlso / OrElse and And / Or seems backwards. Perhaps they should be switched. When can only be used for exception catching. The ability to do a When conditional would be nice for some other things. There is no friggin Refactoring in the VS IDE (not really the language's fault) like there is with C# Not <obj> Is Nothing. Yes, this has been remedied by IsNot, but for some reason I see the Not Is being used too often. (I see it much more frequently with devs who speak english as a second language, does it make better sense from that angle?) It doesn't require the () on ToString() and most functions. (Leads to sloppy coding habits) Having to do _ when breaking a line. It allows optional parameters. (Leads to sloppy coding habits) declaring an array is done by UpperBound and not by capacity. "Dim arr(2) as String" will actually hold 3 elements. Having = be a comparison and assignment operator.

Python:

缺少静态类型 默认参数处理(特别是可以为未来的调用者更改默认参数的事实!) 需要的下划线太多(构造函数必须调用__init__) 缺少适当的私有成员和函数(惯例只是说大多数以下划线开头的东西都是私有的，除了像__getattr__这样的东西不是) 有趣的打印到文件的语法(但他们在Python 3中修复了这个问题)