nil list

Answer
nil and Nil are terms used in various programming languages to represent an empty list or a false value. Here are the key points about nil and Nil:

nil in Emacs Lisp

  • In Emacs Lisp, nil has two meanings: 1) the empty list (), and 2) a false value returned by true-or-false tests.
  • Any value that is not nil (not an empty list) is considered true in Emacs Lisp.
  • nil can be written as () or nil, but nil is conventionally used for false, while () represents the empty list.

Nil in Scala

  • Nil is the idiomatic way to represent an empty list in Scala, as opposed to List().
  • Nil is preferred for creating new empty lists and pattern matching on empty lists.
  • Nil and List() refer to the same object at runtime, but have different static types, which matters for type inference.

List data type in Haskell

  • In Haskell, the List data type is defined using two data constructors: Nil (empty list) and Cons (adds an element to the list).
  • Nil is a nullary constructor (takes no arguments), while Cons takes two arguments: an element of type a and a List a.
  • The List type is recursive because the Cons constructor contains a List a in its definition.
In summary, nil/Nil represents an empty list or a false value in languages like Emacs Lisp, Scala, and Haskell, and is often contrasted with non-empty lists constructed using other means like Cons.
nil list maritime declaration
Answer
A nil list in the context of maritime declarations refers to a document that certifies the absence of certain items or situations on board a vessel. It is typically required by port authorities upon arrival or departure of a ship. Here are the key points about a nil list in maritime declarations:

Purpose

  • The nil list serves as a declaration that certain prohibited or controlled items are not present on the vessel.
  • Common items declared as nil (not present) include firearms, ammunition, stowaways, cigarettes, drugs, and large amounts of cash.

Format

  • It is usually a simple document with statements affirming the absence of the listed items, signed and stamped by the ship's master or captain.
  • Some ports may have specific forms for the nil list, while others accept a general declaration from the master.

Requirement

  • Many ports require a nil list to be submitted as part of the arrival or departure documentation for vessels.
  • It may be combined with other documents like the Maritime Declaration of Health, crew list, cargo manifest, etc.

Relation to Maritime Declaration of Health

  • The Maritime Declaration of Health form also requires listing any crew members, passengers or stowaways who joined the vessel during the voyage.
  • So a nil declaration regarding stowaways is often made in conjunction with the health declaration.
In summary, a nil list is a formal declaration by the ship's master stating that no prohibited or controlled items like weapons, drugs, stowaways, etc. are present on board the vessel, as required by port authorities as part of arrival/departure procedures.
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