ANSI Common Lisp 3 Evaluation and Compilation
Execution of code can be accomplished by a variety of means ranging
from direct interpretation of a form representing a program
to invocation of compiled code produced by a compiler.
Evaluation is the process by which a program is executed in Common Lisp.
The mechanism of evaluation is manifested
both implicitly through the effect of the Lisp read-eval-print loop,
and explicitly through the presence of the functions
Any of these facilities might share the same execution strategy,
or each might use a different one.
The behavior of a conforming program processed by eval
and by compile-file might differ; see Section 188.8.131.52 Semantic Constraints.
Evaluation can be understood in terms of a model in which an
interpreter recursively traverses a form performing each
step of the computation as it goes.
This model, which describes the semantics of Common Lisp programs,
is described in Section 3.1.2 The Evaluation Model.
3.1.1 Introduction to Environments
3.1.2 The Evaluation Model
3.1.3 Lambda Expressions
3.1.4 Closures and Lexical Binding
3.1.7 Return Values