Metaprogramming

Julia is homoiconic, which means that a program can be written symbolically in a way that it can be manipulated as data using the language. This adds great power in as much as the program can create genuine code as it is executing, modifying due to data types, circumstances occurring at runtime, and so on.

The ability of a programming language to be its own metalanguage is termed “reflection”, and this is a valuable language feature to facilitate metaprogramming, popular in list-processing languages such as Lisp.

As remarked on earlier, in compiling its code, problems with long execution times, which arise in most scripting languages, are not present in Julia.

Symbols and expressions

Before discussing macros, we need to understand the role of symbols and expressions in Julia.

The symbol is a type in Julia identified by a colon :() prefix:

julia> :(x)
:x

For complex expressions, combining variables, constants, and functions can also...