|
XL stands for eXtensible Language. It is a computer programming language designed to support concept programming, up to now the only one existing. XL features programmer-reconfigurable syntax and semantics. Compiler ''plug-ins'' can be used to add new features to the language. A base set of plug-ins implements a relatively standard imperative language. Programmers can write their own plug-ins to implement application-specific notations, such as symbolic differentiation, which can then be used similarly to built-in language features. ==Language== XL is defined at four different levels: * XL0 defines how an input text is transformed into a parse tree. * XL1 defines a base language with features comparable to C++. * XL2 defines the standard library, which includes common data types and operators. * XLR defines a dynamic runtime for XL based on XL0. XL has no primitive types nor keywords. All useful operators and data types, like integers or addition, are defined in the standard library (XL2). XL1 is portable between different execution environments. There is no such guarantee for XL2: if a particular CPU does not implement floating-point multiplication, the corresponding operator definition may be missing from the standard library, and using a floating-point multiply may result in a compile-time error. The Hello World program in XL looks like the following: use XL.TEXT_IO WriteLn "Hello World" An alternative form in a style more suitable for large-scale programs would be: import IO = XL.TEXT_IO IO.WriteLn "Hello World" A recursive implementation of factorial in XLR looks like the following: 0! -> 1 N! -> N * (N-1)! 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「XL (programming language)」の詳細全文を読む スポンサード リンク
|