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optimize (Declaration)


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


quality—an optimize quality.

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

Valid Context:

declaration or proclamation


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 neutral value. (quality 3) can be abbreviated to quality.

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

The consequences are unspecified if a quality appears more than once with different values.

 (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))
See Also:

declare, declaim, proclaim, Section 3.3.4 (Declaration Scope)


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).