GBBopen 1.5 Reference -- decf/delete-acons

decf/delete-acons

decf/delete-acons item decrement place &key key test test-not => new-place-value [Macro]

Purpose
Decrement by decrement the value associated with item in an association list stored in place, deleting the cons associated with item if the value becomes zero.

Package :gbbopen-tools

Module :gbbopen-tools

Arguments and values

item		An object
decrement		A number
place		A form which is suitable for use as a generalized reference
key		A function of one argument, or `nil` (default is `nil`)
test		A function of two arguments that returns a generalized boolean (default is `#'eql`)
test-not		A function of two arguments that returns a generalized boolean (use of `:test-not` is deprecated)
new-place-value		An association list

Returns
An association list (the new value of place).

Errors
Item item is not present in the association list stored in place.

Description
This is the inverse of pushnew/incf-acons.

See also
pushnew/incf-acons

Examples

  > (setf alist '((x . 2)(y . 2))
  ((x . 2)(y . 2))
  > (decf/delete-acons 'x 1 alist)
  ((x . 1)(y . 2))
  > (decf/delete-acons 'x 1 alist)
  ((y . 2))
  > (decf/delete-acons 'y 2 alist)
  nil
  >

Note
Declared numeric and pseudo probability versions of decf/delete-acons are also provided: decf&/delete-acons, decf$&/delete-acons, decf$/delete-acons, decf$$/delete-acons, decf$$$/delete-acons, and decf%/delete-acons,

The GBBopen Project

decf/delete-acons