3.8.25 optimize [Declaration]

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

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 Figure 3–25.

  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.

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))
     ))

See Also::

declare, declaim , proclaim , Declaration Scope

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 Declaration Scope.