Editing Generic programming (section)

=====Code generation=====
In addition to template metaprogramming, D also provides several features to enable compile-time code generation:
* The <code>import</code> expression allows reading a file from disk and using its contents as a string expression.
* Compile-time reflection allows enumerating and inspecting declarations and their members during compiling.
* User-defined [[Attribute (computing)|attributes]] allow users to attach arbitrary identifiers to declarations, which can then be enumerated using compile-time reflection.
* [[Compile-time function execution]] (CTFE) allows a subset of D (restricted to safe operations) to be interpreted during compiling.
* String mixins allow evaluating and compiling the contents of a string expression as D code that becomes part of the program.

Combining the above allows generating code based on existing declarations.
For example, D serialization frameworks can enumerate a type's members and generate specialized functions for each serialized type
to perform serialization and deserialization.
User-defined attributes could further indicate serialization rules.

The <code>import</code> expression and compile-time function execution also allow efficiently implementing [[domain-specific language]]s.
For example, given a function that takes a string containing an HTML template and returns equivalent D source code, it is possible to use it in the following way:

<syntaxhighlight lang="d">
// Import the contents of example.htt as a string manifest constant.
enum htmlTemplate = import("example.htt");

// Transpile the HTML template to D code.
enum htmlDCode = htmlTemplateToD(htmlTemplate);

// Paste the contents of htmlDCode as D code.
mixin(htmlDCode);
</syntaxhighlight>