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(slib.info)Feature

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Feature
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SLIB denotes "features" by symbols.  SLIB maintains a list of features
supported by the Scheme "session".  The set of features provided by a
session may change over time.  Some features are properties of the
Scheme implementation being used.  The following features detail what
sort of numbers are available from an implementation.

   * 'inexact

   * 'rational

   * 'real

   * 'complex

   * 'bignum

Other features correspond to the presence of sets of Scheme procedures
or syntax (macros).

 - Function: provided? feature
     Returns `#t' if FEATURE is supported by the current Scheme session.

 - Procedure: provide feature
     Informs SLIB that FEATURE is supported.  Henceforth `(provided?
     FEATURE)' will return `#t'.

     (provided? 'foo)    => #f
     (provide 'foo)
     (provided? 'foo)    => #t