dynamic-typing

问题 In programming language what is the difference between Inferred Type and Dynamic typing? I know about Dynamic typing but don't get how dynamic typing is differ from Inferred Type and how? Could someone please provide explanation with some example? 回答1: Inferred type = set ONCE and at compile time. Actually the inferred part is only a time saver in that you don't have to type the Typename IF the compiler can figure it out. Type Inference is often used in conjunction static typing (as is the

来源： https://stackoverflow.com/questions/38366857/how-does-python-interpreter-work-in-dynamic-typing

来源： https://stackoverflow.com/questions/38366857/how-does-python-interpreter-work-in-dynamic-typing

问题 According to Wikipedia Computer scientists consider a language "type-safe" if it does not allow operations or conversions that violate the rules of the type system. Since Python runtime checks ensure that type system rules are satisfied, we should consider Python a type safe language. The same point is made by Jason Orendorff and Jim Blandy in Programming Rust: Note that being type safe is independent of whether a language checks types at compile time or at run time: C checks at compile time,

问题 Say I have the following two types: export type CollectionNames = 'twitter:tweets' | 'twitter:users' | 'twitter:metadata-cashtag' export type CollectionType<T extends CollectionNames> = T extends 'twitter:tweets' ? Tweet : T extends 'twitter:users' ? User : T extends 'twitter:metadata-cashtag' ? CashtagMetadataDb : never I feel this is very clunky and I'm not very keen on having the strings twice. Also it's possible to legally misspell them in the latter type. Is there any way to create these

问题 I have a situation where I am at the moment using the extremely scary function unsafeCoerce. It's not for anything important fortunately, but I was wondering whether this seems to be a safe usage of this function, or whether there would be another way to solve this particular problem that other people know of. The code I have is something like the following: data Token b = Token !Integer identical :: Token a -> Token b -> Bool identical (Token a) (Token b) = a == b data F a = forall b. F

问题 I am new to Ruby and currently trying a few examples from the Ruby book I am using as a guide: class Account attr_accessor :balance def initialize(balance) @balance = balance end end class Transaction def initialize(account_a, account_b) @account_a = account_a @account_b = account_b end def debit(account,amount) account.balance -= amount end def credit(account,amount) account.balance += amount end def transfer(amount) debit(@account_a, amount) credit(@account_b, amount) end end savings =

问题 I need to cast a return value to a specific type that I need to keep dynamic, like let cellType = "CellTypeToBeResolved" cell = (tableView.dequeueReusableCellWithIdentifier("myID") as? CellTypeToBeResolved)! How is this possible in Swift 2.0? Thnx! 回答1: You can't do it, because Swift is (deliberately) missing not one but two pieces of the puzzle: You can't turn a string into a class. More important, you can't cast down to a class expressed as a variable. The class to cast down to must be a

问题 I implemented an extension to NSObject to get the dynamic type of my objects: extension NSObject { var dynamic_type : String { get { return String(describing: type(of: self)) } } } This works perfectly for public classes. In a class called InitialState dynamic_type would be "InitialState" (this is what I want) But as soon as I change the class to private or fileprivate it is something like "(InitialState in _AF5C6D4A3B423A6F0735A7740F802E5A)" (the parenthesis are also returned) Why is this

问题 I'm still fairly new to Python and I'm trying to get used to its dynamic typing. Sometimes I have a function or a class that expects a parameter of a certain type, but could get a value of another type that's coercible to it. For example, it might expect a float but instead receive an int or a decimal. Or it might expect a string, but instead receive an object that defines the __str__ special method. What is the best practice for coercing the argument to the right type (and the reason for it)