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Node:Generic Function Internals, Next:Extending Guiles Primitives, Previous:Basic Generic Function Creation, Up:Creating Generic Functions
3.5.2 Generic Function Internals
define-generic calls ensure-generic to upgrade a pre-existing procedure value, or make with metaclass<generic> to create a new generic function.
define-accessor calls ensure-accessor to upgrade a pre-existing procedure value, or make-accessor to create a new accessor.
| ensure-generic old-definition [name] | procedure |
|---|
Return a generic function with name name, if possible by using or upgrading old-definition. If unspecified, name defaults to#f.
If old-definition is already a generic function, it is returned unchanged.
If old-definition is a Scheme procedure or procedure-with-setter,ensure-generic returns a new generic function that usesold-definition for its default procedure and setter.
Otherwise ensure-generic returns a new generic function with no defaults and no methods.
| make-generic [name] | procedure |
|---|
Return a new generic function with name (car name). If unspecified, name defaults to #f.
ensure-generic calls make with metaclasses<generic> and <generic-with-setter>, depending on the previous value of the variable that it is trying to upgrade.
make-generic is a simple wrapper for make with metaclass<generic>.
| ensure-accessor proc [name] | procedure |
|---|
Return an accessor with name name, if possible by using or upgrading proc. If unspecified, name defaults to #f.
If proc is already an accessor, it is returned unchanged.
If proc is a Scheme procedure, procedure-with-setter or generic function, ensure-accessor returns an accessor that reuses the reusable elements of proc.
Otherwise ensure-accessor returns a new accessor with no defaults and no methods.
| make-accessor [name] | procedure |
|---|
Return a new accessor with name (car name). If unspecified, name defaults to #f.
ensure-accessor calls make with metaclass <generic-with-setter>, as well as calls toensure-generic, make-accessor and (tail recursively)ensure-accessor.
make-accessor calls make twice, first with metaclass <generic> to create a generic function for the setter, then with metaclass <generic-with-setter> to create the accessor, passing the setter generic function as the value of the#:setter keyword.