(goops.info.gz) Basic Generic Function Creation

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(goops.info.gz) Creating Generic Functions

(goops.info.gz) Generic Function Internals

 
 Basic Generic Function Creation
 -------------------------------
 
 The following forms may be used to bind a variable to a generic
 function.  Depending on that variable's pre-existing value, the generic
 function may be created empty - with no methods - or it may contain
 methods that are inferred from the pre-existing value.
 
 It is not, in general, necessary to use `define-generic' or
 `define-accessor' before defining methods for the generic function
 using `define-method', since `define-method' will automatically
 interpolate a `define-generic' call, or upgrade an existing generic to
 an accessor, if that is implied by the `define-method' call.  Note in
 particular that, if the specified variable already has a _generic
 function_ value, `define-generic' and `define-accessor' will _discard_
 it!  Obviously it is application-dependent whether this is desirable or
 not.
 
 If, for example, you wanted to extend `+' for a class representing a
 new numerical type, you probably want to inherit any existing methods
 for `+' and so should not use `define-generic'.  If, on the other hand,
 you do not want to risk inheriting methods whose behaviour might
 surprise you, you can use `define-generic' or `define-accessor' to wipe
 the slate clean.
 
  - syntax: define-generic symbol
      Create a generic function with name SYMBOL and bind it to the
      variable SYMBOL.
 
      If the variable SYMBOL was previously bound to a Scheme procedure
      (or procedure-with-setter), the old procedure (and setter) is
      incorporated into the new generic function as its default
      procedure (and setter).  Any other previous value that was bound
      to SYMBOL, including an existing generic function, is overwritten
      by the new generic function.
 
  - syntax: define-accessor symbol
      Create an accessor with name SYMBOL and bind it to the variable
      SYMBOL.
 
      If the variable SYMBOL was previously bound to a Scheme procedure
      (or procedure-with-setter), the old procedure (and setter) is
      incorporated into the new accessor as its default procedure (and
      setter).  Any other previous value that was bound to SYMBOL,
      including an existing generic function or accessor, is overwritten
      by the new definition.
 

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(goops.info.gz) Creating Generic Functions

(goops.info.gz) Generic Function Internals