Processing of Top Level Forms (original) (raw)

Processing of top level forms in the file compiler is defined as follows:

1. If the form is a compiler macro form(not disabled by a notinline declaration), the implementation might or might not choose to compute the compiler macro expansion of the form and, having performed the expansion, might or might not choose to process the result as a top level form in the same processing mode (compile-time-too or not-compile-time). If it declines to obtain or use the expansion, it must process the original form.
2. If the form is a macro form, its macro expansion is computed and processed as a top level form in the same processing mode (compile-time-too or not-compile-time).
3. If the form is a progn form, each of its body forms is sequentially processed as a top level form in the same processing mode.
4. If the form is a locally, macrolet, or symbol-macrolet, compile-file establishes the appropriate bindings and processes the body forms as top level forms with those bindings in effect in the same processing mode. (Note that this implies that the lexical_environment_ in which top level forms are processed is not necessarily the null lexical environment.)

5. If the form is an eval-when form, it is handled according to the next figure.
EVAL-WHEN processing

CT	LT	E	Mode	Action	New Mode
Yes	Yes	---	---	Process	compile-time-too
No	Yes	Yes	CTT	Process	compile-time-too
No	Yes	Yes	NCT	Process	not-compile-time
No	Yes	No	---	Process	not-compile-time
Yes	No	---	---	Evaluate	---
No	No	Yes	CTT	Evaluate	---
No	No	Yes	NCT	Discard	---
No	No	No	---	Discard	---
Column CT indicates whether :compile-toplevel is specified. Column LT indicates whether :load-toplevel is specified. Column E indicates whether :execute is specified. Column Mode indicates the processing mode; a dash ( - ) indicates that the processing mode is not relevant.
The Action column specifies one of three actions:

Process: process the body as top level forms in the specified mode.
Evaluate: evaluate the body in the dynamic execution context of the compiler, using the evaluation environment as the global environment and the lexical environment in which the eval-when appears.
Discard: ignore the form.
The New Mode column indicates the new processing mode. A dash ( - ) indicates the compiler remains in its current mode.

6. Otherwise, the form is a top level form that is not one of the special cases. In compile-time-too mode, the compiler first evaluates the form in the evaluation environment and then minimally compiles it. In not-compile-time mode, the form is simply minimally compiled. All subformsare treated as non-top-level forms.
Note that top level forms are processed in the order in which they textually appear in the file and that each top level form read by the compiler is processed before the next is read. However, the order of processing (including macro expansion) ofsubforms that are not top level forms and the order of further compilation is unspecified as long as Common Lisp semantics are preserved.

eval-when forms cause compile-time evaluation only at top level. Both :compile-toplevel and :load-toplevel situation specifications are ignored for non-top-level forms. For non-top-level forms, an eval-whenspecifying the :execute situation is treated as an _implicit progn_including the forms in the body of the eval-when form; otherwise, the forms in the body are ignored.