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6.12 Environments and evaluation

eval library procedure: environment list₁… ¶

This procedure returns a specifier for the environment that results by starting with an empty environment and then importing each list, considered as an import set, into it. (See Libraries for a description of import sets.) The bindings of the environment represented by the specifier are immutable, as is the environment itself.

r5rs library procedure: scheme-report-environment version ¶

If version is equal to 5, corresponding to R⁵RS, scheme-report-environment returns a specifier for an environment that contains only the bindings defined in the R⁵RS library. Implementations must support this value of version.

Implementations may also support other values of version, in which case they return a specifier for an environment containing bindings corresponding to the specified version of the report. If version is neither 5 nor another value supported by the implementation, an error is signaled.

The effect of defining or assigning (through the use of eval) an identifier bound in a null-environment (for example car) is unspecified. Thus both the environment and the bindings it contains may be immutable.

r5rs library procedure: null-environment version ¶

If version is equal to 5, corresponding to R⁵RS, the null-environment procedure returns a specifier for an environment that contains only the bindings for all syntactic keywords defined in the R⁵RS library. Implementations must support this value of version.

Implementations may also support other values of version, in which case they return a specifier for an environment containing appropriate bindings corresponding to the specified version of the report. If version is neither 5 nor another value supported by the implementation, an error is signaled.

The effect of defining or assigning (through the use of eval) an identifier bound in a scheme-report-environment (for example car) is unspecified. Thus both the environment and the bindings it contains may be immutable.

repl library procedure: interaction-environment ¶

This procedure returns a specifier for a mutable environment that contains an implementation-defined set of bindings, typically a superset of those exported by (scheme base). The intent is that this procedure will return the environment in which the implementation would evaluate expressions entered by the user into a REPL.

eval library procedure: eval expr-or-def environment-specifier ¶

If expr-or-def is an expression, it is evaluated in the specified environment and its values are returned. If it is a definition, the specified identifier(s) are defined in the specified environment, provided the environment is not immutable. Implementations may extend eval to allow other objects.

(eval '(* 7 3) (environment '(scheme base))) ⇒  21

(let ((f (eval '(lambda (f x) (f x x))
               (null-environment 5))))
  (f + 10))
    ⇒  20
(eval '(define foo 32)
      (environment '(scheme base)))
    ⇒ error is signaled