The (r6rs eval) library allows a program to create Scheme expressions as data at run time and evaluate them.
Evaluates expression in the specified environment and returns its value. Expression must be a valid Scheme expression represented as a datum value, and environment-specifier must be a library specifier, which can be created using the environment procedure described below.
If the first argument to eval is not a syntactically correct expression, then eval must raise an exception with condition type &syntax. Specifically, if the first argument to eval is a definition or a splicing begin form containing a definition, it must raise an exception with condition type &syntax.
Import-spec must be a datum representing an <import spec> (see report section on “Library form”). The environment procedure returns an environment corresponding to import-spec
The bindings of the environment represented by the specifier are immutable: If eval is applied to an expression that attempts to assign to one of the variables of the environment, eval must raise an exception with a condition type &assertion.
(library (foo)