Remove ads
In the programming language Lisp, the reader or read function is the parser which converts the textual form of Lisp objects to the corresponding internal object structure.
In the original Lisp, S-expressions consisted only of symbols, integers, and the list constructors ( xi... ) and (x . y). Later Lisps, culminating in Common Lisp, added literals for floating-point, complex, and rational numbers, strings, and constructors for vectors.
The reader is responsible for parsing list structure, interning symbols, converting numbers to internal form, and calling read macros.
Remove ads
The reader is controlled by the readtable, which defines the meaning of each character.
Unlike most programming languages, Lisp supports parse-time execution of programs, called "read macros" or "reader macros". These are used to extend the syntax either in universal or program-specific ways. For example, the quoted form (quote x) operator can be abbreviated as 'x. The ' operator can be defined as a read macro which reads the following list and wraps it with quote. Similarly, the backquote operator (` ) can be defined as a read macro.
Wikiwand in your browser!
Seamless Wikipedia browsing. On steroids.
Every time you click a link to Wikipedia, Wiktionary or Wikiquote in your browser's search results, it will show the modern Wikiwand interface.
Wikiwand extension is a five stars, simple, with minimum permission required to keep your browsing private, safe and transparent.
Remove ads