You can associate arbitrary properties with any procedure.
Each property is a (
value)-pair. Usually the
key is a symbol, but it can be any object.
(define my-car (lambda (arg) setter: my-set-car (primitive-car arg)))
The system uses certain internal properties:
'name refers to the name used when a procedure is printed;
'emacs-interactive is used to implement Emacs
'setter is used to associate a
Get the property value corresponding to the given
prochas no property with the given
default(which defaults to
Associate the given
To change the print name of the standard
+ procedure (probably
not a good idea!), you could do:
(set-procedure-property! + 'name 'PLUS)
Note this only changes the name property used for printing:
+ ⇒ #<procedure PLUS> (+ 2 3) ⇒ 5 (PLUS 3 4) ⇒ ERROR
As a matter of style, it is cleaner to use the
form, as it is a more declarative interface.
nameas a compound procedure consisting of the specified
methods, with the associated properties. Applying
nameselect the "best"
method, and applies that. See the following section on generic procedures.
For example, the standard
vector-refprocedure specifies one method, as well as the
setterproperty:(define-procedure vector-ref setter: vector-set! (lambda (vector::vector k ::int) (invoke vector 'get k)))
You can also specify properties in the lambda body:
(define (vector-ref vector::vector k ::int) setter: vector-set! (invoke vector 'get k))
The name of a procedure (as a symbol), which is used when the procedure is printed.
Set the setter procedure associated with the procedure.
Used during the validation phase of the compiler.
Used during the bytecode-generation phase of the compiler: If we see a call to a known function with this property, we can emit custom bytecode for the call.