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Chapter 9

9 Macros

Macros are without a doubt the most advanced feature in Haxe. They are often perceived as dark
magic that only a select few are capable of mastering, yet there is nothing magical (and certainly
nothing dark) about them.

Definition: Abstract Syntax Tree (AST)

The AST is the result ofparsingHaxe code into a typed structure. This structure is exposed

to macros through the types defined in the filehaxe/macro/Expr.hxof the Haxe Standard

Library.

Source code Lexer / Parser Abstract Syntax Tree (AST)

• Expression


• Complex Type


• haxe.macro.Expr

Macro processor

Typed AST Typer Abstract Syntax Tree (AST)

• Typed Expression


• Type


• haxe.macro.Type

Generator

Output

parse

transform

type

generate

Figure 9.1: The role of macros during compilation.

A basic macro is asyntax-transformation. It receives zero or more expressions ( 5 ) and also