Contents|Symbol Index|Up: Chapter 3 Dictionary|Prev: declaration|Next: special

Declaration `optimize`

Syntax:

(optimize {quality | (quality value)}^*)

Arguments:

quality—an optimize quality.

value—one of the integers 0, 1, 2, or 3.

Valid Context:

declaration or proclamation

Binding Types Affected:

None.

Description:

Advises the compiler that each quality should be given attention according to the specified corresponding value. Each quality must be a symbol naming an optimize quality; the names and meanings of the standard optimize qualities are shown in the next figure.

Name	Meaning
`compilation-speed`	speed of the compilation process
`debug`	ease of debugging
`safety`	run-time error checking
`space`	both code size and run-time space
`speed`	speed of the object code

Figure 3–25. Optimize qualities

There may be other, implementation-defined optimize qualities.

A value 0 means that the corresponding quality is totally unimportant, and 3 that the quality is extremely important; 1 and 2 are intermediate values, with 1 the "average" -> "neutral" since KAB balked and I think this will be less weird. -kmp 3-Oct-91 averageneutral value. (quality 3) can be abbreviated to quality. This declaration is \term{pervasive}.

Note that code which has the optimization (safety 3), or just safety, is called safe code.

Added per Sandra in response to Barrett query ...The consequences are unspecified if a quality appears more than once with different values.

Examples:

 (defun often-used-subroutine (x y)
   (declare (optimize (safety 2)))
   (error-check x y)
   (hairy-setup x)
   (do ((i 0 (+ i 1))
        (z x (cdr z)))
       ((null z))
     ;; This inner loop really needs to burn.
     (declare (optimize speed))
     (declare (fixnum i))
     ))

Notes:

An optimize declaration never applies to either a variable or a function binding. An optimize declaration can only be a free declaration. For more information, see Section 3.3.4 (Declaration Scope).