188.8.131.52 Feature Expressions
Boolean combinations of features, called feature expressions, are used by the #+ and #- reader macros in order to direct conditional reading of expressions by the Lisp reader.
The rules for interpreting a feature expression are as follows:
If a symbol naming a feature is used as a feature expression, the feature expression succeeds if that feature is present; otherwise it fails.
- (not feature-conditional)
A not feature expression succeeds if its argument feature-conditional fails; otherwise, it succeeds.
- (and feature-conditional*)
An and feature expression succeeds if all of its argument feature-conditionals succeed; otherwise, it fails.
- (or feature-conditional*)
An or feature expression succeeds if any of its argument feature-conditionals succeed; otherwise, it fails.
184.108.40.206.1 Examples of Feature Expressions
Copyright 1996-2005, LispWorks Ltd. All rights reserved.