(r5rs.info.gz) Eval

(r5rs.info.gz) Standard procedures
 
 6.5 Eval
 ========
 
  -- procedure: eval expression environment-specifier
      Evaluates EXPRESSION in the specified environment and returns its
      value.  EXPRESSION must be a valid Scheme expression represented
      as data, and ENVIRONMENT-SPECIFIER must be a value returned by one
      of the three procedures described below.  Implementations may
      extend `eval' to allow non-expression programs (definitions) as
      the first argument and to allow other values as environments, with
      the restriction that `eval' is not allowed to create new bindings
      in the environments associated with `null-environment' or
      `scheme-report-environment'.
 
      (eval '(* 7 3) (scheme-report-environment 5))
                                                         ==>  21
 
      (let ((f (eval '(lambda (f x) (f x x))
                     (null-environment 5))))
        (f + 10))
                                                         ==>  20
 
 
  -- procedure: scheme-report-environment version
  -- procedure: null-environment version
      VERSION must be the exact integer `5', corresponding to this
      revision of the Scheme report (the Revised^5 Report on Scheme).
      `Scheme-report-environment' returns a specifier for an environment
      that is empty except for all bindings defined in this report that
      are either required or both optional and supported by the
      implementation. `Null-environment' returns a specifier for an
      environment that is empty except for the (syntactic) bindings for
      all syntactic keywords defined in this report that are either
      required or both optional and supported by the implementation.
 
      Other values of VERSION can be used to specify environments
      matching past revisions of this report, but their support is not
      required.  An implementation will signal an error if VERSION is
      neither `5' nor another value supported by the implementation.
 
      The effect of assigning (through the use of `eval') a variable
      bound in a `scheme-report-environment' (for example `car') is
      unspecified.  Thus the environments specified by
      `scheme-report-environment' may be immutable.
 
 
  -- optional procedure: interaction-environment
      This procedure returns a specifier for the environment that
      contains implementation-defined bindings, typically a superset of
      those listed in the report.  The intent is that this procedure
      will return the environment in which the implementation would
      evaluate expressions dynamically typed by the user.
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