翻訳と辞書 Words near each other ・ Null sign ・ Null Stern Hotel ・ Null Subject Parameter ・ Null symbol ・ Null vector ・ Null vector (disambiguation) ・ Null-A Three ・ Null-move heuristic ・ Null-O ・ Null-subject language ・ Null-terminated string ・ Nulla bona ・ Nulla in mundo pax sincera ・ Nulla poena pro vitium Abyssus ・ Nulla poena sine lege ・ Nullable type ・ Nullagine River ・ Nullagine, Western Australia ・ Nullah ・ Nullah (disambiguation) ・ Nullarbor (demo party) ・ Nullarbor (disambiguation) ・ Nullarbor dwarf bettong ・ Nullarbor Links ・ Nullarbor National Park ・ Nullarbor Nymph ・ Nullarbor Plain ・ Nullarbor quail-thrush ・ Nullarbor Regional Reserve ・ Nullarbor Wilderness Protection Area Dictionary Lists mini英和辞書 mini和英辞書 Webster 1913 Latin-English FOLDOC Wikipedia English ウィキペディア

翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Nullable type ： ウィキペディア英語版 Nullable type In programming, nullable types are a feature of the type system of some programming languages which allow the value to be set to the special value NULL instead of the usual possible values of the data type. In statically-typed languages, a nullable type is an option type (in functional programming terms), while in dynamically-typed languages (where values have types, but variables do not), equivalent behavior is provided by having a single null value. Primitive types such as integers and booleans cannot generally be null, but the corresponding nullable types (nullable integer and nullable boolean, respectively) can also assume the NULL value. NULL is frequently used to represent a missing value or invalid value, such as from a function that failed to return or a missing field in a database, as in NULL in SQL. ==Example== An integer variable may represent integers, but 0 (zero) is a special case because 0 in many programming languages can mean "false". Also this doesn't give us any notion of saying that the variable is empty, a need for which occurs in many circumstances. This need can be achieved with a nullable type. In programming languages like C# 2.0, a nullable integer, for example, can be declared by a question mark (int? x). In programming languages like C# 1.0, nullable types can be defined by an external library as new types (e.g. NullableInteger, NullableBoolean). A boolean variable makes the effect more clear. Its values can be either "true" or "false", while a nullable boolean may also contain a representation for "undecided". However, the interpretation or treatment of a logical operation involving such a variable depends on the language. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Nullable type」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.