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D is an object-oriented, imperative, multiparadigm system programming language by Walter Bright of Digital Mars. It originated as a re-engineering of C++, but even though it is predominately influenced by that language, it is not a variant of C++. D has redesigned some C++ features and has been influenced by concepts used in other programming languages.
Features NOTE: The feature set and detailed design of the language is not quite finalized as of the time of this writing. D is being designed with lessons learned from practical C++ usage rather than from a theoretical perspective. It uses many C++ concepts but discards some, such as strict backwards compatibility with C source code. It adds to the functionality of C++ by also implementing design by contract, unit testing, true modules, automatic memory management (garbage collection), first class arrays, associative arrays, dynamic arrays, array slicing, nested functions, inner classes, closures (anonymous functions), lazy evaluation and has a reengineered template syntax. D retains C++'s ability to do low-level coding, and adds to it with support for an integrated inline assembler. C++ multiple inheritance is replaced by single inheritance with interfaces and mixins. D's declaration, statement and expression syntax closely matches that of C++. The inline assembler typifies the differences between D and application languages like Java and C#. An inline assembler lets programmers enter machine-specific assembly code in with standard D code—a technique often used by systems programmers to access the low-level features of the processor needed to run programs that interface directly with the underlying hardware, such as operating systems and device drivers. D has built-in support for embedded documentation comments (called Ddoc), but so far only the compiler supplied by DigitalMars implements a documentation generator. Memory management Memory is usually managed with garbage collection, but specific objects can be finalized immediately when they go out of scope. Explicit memory management is possible using the overloaded operators new and delete, as well as simply calling C's malloc and free directly. It is also possible to disable garbage collection for individual objects, or even for the entire program if more control over memory management is desired. The manual gives numerous examples as to how to implement different extremely optimized memory management schemes when garbage collection won't quite do it for part of the program. Interaction with other systems C's ABI (Application Binary Interface) is supported as well as all of C's fundamental and derived types, enabling direct access to existing C code and libraries. C's standard library is part of standard D. Unless you use very explicit namespaces it can be somewhat messy to access, as it is spread throughout the D modules that use it -- but the pure D standard library is usually sufficient unless interfacing with C code. C++'s ABI is not supported, although D can access C++ code that is written to the C ABI, and can access C++ COM (Component Object Model) code. The D parser understands an extern (C++) calling convention for linking to C++ objects, but it is not yet implemented. Implementation Current D implementations compile directly into native code for efficient execution. D is still under development, and changes to the language are made regularly. Although the design is almost frozen, it is possible that some of these changes could break D programs written for older versions of the language and compiler. The official compiler by Walter Bright defines the language itself, and it is currently in the beta testing state. Examples Keywords are in , strings in , comments in . Example 1 This example program prints its command line arguments. The main function is the entry point of a D program, and args is an array of strings representing the command line arguments. A string in D is an array of characters, represented by char. std.stdio; main( args) The foreach statement can iterate over any collection, in this case it is producing a sequence of keys (i) and values (a) from the array args. Example 2 This illustrates the use of associative arrays to build much more complex data structures. std.stdio; main() display_item_count( person, items) Example 3 This heavily annotated example highlights many of the differences from C++, while still retaining some C++ aspects. std.stdio; main( args) CmdLin See also | |||||||||||||||||||||||||||
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